GEOL 4331: Intro To GIS: Exam I Review
What must a surveyor do if he is using a GPS enabled smartpole stadia rod but the GPS sateillite are obsructed from view?
A laser to the line of sight of a SmartStation
Satellites require these types of clocks.
ATOMIC CLOCK.
What increases as the Conceptual Model goes down the levels?
Abstraction
True Direction
Angular relationship are represented correctly
Define some of the features in a Vector Dataset.
- Contain, points, lines & polygons of real or imaginary features on Earth - Downloadable Vector Data - GPS Data collected All Day without sleep - Metadata describes the data but is missing
Emits energy in order to scan objects whereupon a sensor then detects and measures the radiation that is reflected or backscattered from the targe
Active Remote Sensing
Two Main Image Types
Aerial Photographs Satellite Images
Data to Info Conversion (Remote Sensing)
Analog visual Image Processing (using the Element of image Interpretation) Digital Image Processing Hypothesis Testing
Characteristics of Great Circles
1. Every great circle divide Earth into two equal halves called hemispheres 2. Every great circle is a circumference of the Earth 3. Great circles mark the shortest travel routes between locations on earth's surface
Industry Growth In China
2012(30%) and growth by 20%. 81 Billion By 2015 and 163 Billion By 2020. 23,000 Organizations in'volved in China
What is the mean radius of the Earth?
3,959 miles 6, 371.3 Km
Recreation
3-10m $400
At least ______ satellites are in line of sight from almost anywhere on Earth's surface
4
China GTECH Industry Value
42 Billion
Texas NAD83 State Plane Zones
4201 (North), 4202 (North-Central?), 4203 (Central), 4204 (South Central), 4205 (South)
Combination of scanning and manual digitizing.
Heads up digitizing
Mouse on a screen. Digitizes paper maps, aerial photos, or other images
Heads up digitizing
What is a Object Based Vector Model?
In this model, spatial data are treated as objects, i.e., roads, rivers, lakes, parks, etc. Objects contain all of the info and properties to define the object All of them are stored in a single system
Integer
In which case there is an associated value attribute table (VAT) which contains one record for each different value in the raster
What increases as Green leaves absorb more red and blue light
Increase in NIR reflectance
IRNSS
India. Initiated 2006. Being deployed. 1st satellite in 2011
Most error in standard GPS
Selective Availability
is an intentional degradation of the signal once imposed by the U.S. Department of Defense; turned off SA in May 2000
Selective Availability (SA)
Vector data Model
Defined Spatially Point (x and y Coordinates) Line (sequence of Points) Polygon (a closed Set of Lines) Good for representing clearly defined objects
Projected Coordinate System
Defined on a flat, two-dimensional surface. Unlike a geographic coordinate system, a projected coordinate system has constant lengths, angles, and areas across the two dimensions.
A simple geometric form capable of projecting information from globe without compressing or stretching
Developable Surfaces
Distance from satellite
Difference in time from satellite to time received gives distance from satellite. T0 is signal from satellite T1 is signal from receiver therefore D = Speed of Light x (T1 - T0)
....uses the time sequence of observed errors at fixed locations to adjust simultaneous measurements at mobile receivers
Differential GPS
..simultaneous GPS measurements at field-roving (unknown) and base (known) sites
Differential GPS
More accurate measurements if this instrument is left in place longer
Differential GPS
DOQQs
Digital Ortho Quarter Quads - Grayscale or color-infrared (CIR) images - 1-meter ground resolution; - Referenced to the North American Datum of 1983 (NAD83) and cast on the Universal Transverse Mercator (UTM) projection
The process where features on a map or image are converted into digital format for use by a GIS
Digitizing
Advantage of CAD?
Digitizing precision
- Used to digitize hard copy maps into GIS - Transform wire intersections into coordinates of the tablet's coordinate system
Digitizing tablets (Heads down digitizing)
What are The components of A Thematic Map?
Geographic Baseman of The World > Thematic overlay of The world's Largest Cities > Composite of Both maps
What is Visualized on Maps?
Geography
In plane-table survey a special telescope alidade is placed on a leveled plane-table. A line is drawn from the center of the table in the direction of feature of interest, outcrop, tree etc
True
Interval and Ratio data present continuous phenomena and are usually measured with real cell values
True
Latitude goes from 0 to 90º N or S and longitude to 180 º E or W of meridian; the 180 º line is the date line
True
Latitude is North/South of equator. And Longitude West/East of the Prime Meridian.
True
Latitude lines form parallel circles of different sizes, while longitude lines are half-circles that meet at the poles
True
Lines of Lat and Long constitute the Earth's Graticule
True
MAP Ratios are Dimensionless
True
Most GPS are set to WGS84 out-of-the-box (same as NAD83)
True
Multiband Rasters are often displayed as red-green-blue composites.
True
NAD 27 resulted in lat/long coordinates for about 26,000 survey points in the US and Canada.
True
Nominal and Ordinal data represent discrete categories and are represented in integer cell values
True
On-screen digitizing also removes or reduces the need for digitizing tables or map scanners
True
On-screen digitizing is often more accurate than manual digitizing because manual map digitization is often limited by the pointing ability of the operator
True
Originally, the "datum" referred to that "ultimate reference point."
True
Posidonius made measurement using angles to star in near horizon, 38, 600 km
True
Qualitative Maps Are based on descriptive Information(Nominal)
True
Quantitative maps may Use Numerical relationship Between Variables That have been Mapped
True
Reflectance, transmittance, and absorbtance are typically given as a percentage. No units
True
Satellites started collecting geodetic information in 1962 as part of National Geodetic Survey
True
Short segments of pseudo-random codes are unique for each satellite & time
True
Snapping may join nodes, or may place a node onto a nearby line segment
True
Spaghetti data model records each line separately and a shared boundary between polygon can be represented twice.
True
The Spherical Model uses the distance from the hypothetical center of the Earth to the surface (radius).
True
The basis of GPS is triangulation from satellites
True
The circle formed by a slice that does not pass through the center is a small circle (all lines of latitude except the equator are small circles)
True
The ellipsoid is an approximation of the Earth's shape that does not account for variations caused by non-uniform density of the Earth.
True
The feature is the arc, not the line.
True
The geoid is actually measured and interpolated, using gravitational measurements
True
The higher the PDOP value, the poorer the measurement
True
The intersection of Central Meridian of UTM zone and the Equator is the origin of the zone.
True
The sphere is the simplest model of Earth's surface.
True
The surface of the geoid extends across the Earth, approximately at mean sea level at a level set by gravity
True
Thematic Maps Can Show quantitative or qualitative information
True
This height above a geoid is also called the orthometric height
True
Topological info is used to detect errors in spatial data.
True
UTM coordinates are in meters, making it easy to make accurate calculations of short distances between points (error is less than 0.04%).
True
UTM system is transverse cylindrical projection, dividing the surface of the Earth 60 zones, each 6 degree of longitude wide, with the central meridian in the center of the zone.
True
Vegetation indices express the difference between NIR and red reflectance
True
WAAS Only available in North America and Ideal for open land and marine applications
True
You must correct for any delays the signal experiences as it travels through the atmosphere (positional uncertainty)
True
cesium can be used to create extraordinarily precise clock
True
early atomic clocks looked at vibrations of quartz crystal
True
if you have few Points Then you Should Use Size instead of Color value
True
the distance in curvature of a degree of longitude is not constant
True
• In NAD27 center point was Mead's Ranch, KS
True
Force of gravity responds to changes in water volume. Gravity is varying in time and space.
True Water is heavy.
An Object Class is a collection of objects in tabular format that have the same behavior and the same attributes.
True An object class is a table that has a unique identifier (ObjectID) for each record
The shortest distance between two points on the sphere is an arc of a great circle
True Defined by slicing the sphere through the two points and the center (all lines of longitude, and the equator, are great circles).
Globe is nearly a perfect model of our planet
True Displays relationship between landforms and water bodies, relative size and shape of features, and accurate compass directions
Anaximenes believed that the Earth was a rectangular box
True.
Newton and other suggested Earth must be flattened because of centrifugal forces
True.
Raster Models are useful for background maps and for spatial analysis
True.
A Relationship is an association or link between two objects in a database.
True. A relationship can exist between spatial objects (features in feature classes), non-spatial objects (objects in object classes), or between spatial and non-spatial objects.
At 1 degree Longitude you can calculate the rest of the Earth....
True. 1 degree Longitude = 111 x Cos(latitude)
Monochromatic color Scale are A Series of Colors of The Same hue But with Color value Varied from Low to High
True. Common for Choropleth Maps Darker Colors = More Importance
A feature class is a collection of geographic objects in tabular format that have the same behavior and the same attributes
True. Feature Class = Object class + spatial coordinates
In a Simple Raster one value is assigned per cell
True. Integer as a code example: limestone = 1, sandstone = 2, mudstone = 3 -One Raster per theme (Geology>Hydrography>Parcels)
The distance in curvature of a degree of latitude is always equal to about 111 km
True. 110 Km?
The U. S. Air Force lunches, maintains and constantly monitors exact location and of each GPS satellites through ground stations
True. Control Segment
A location measurement accurate to 1 cm horizontally and 2cm vertically is now possible in 3 minutes with a mobile receiver
True. Differential GPS
Saturation is a color Scale That goes from Pure Hue To gray or Black
True. Example Would be from Red To Black
Value is the amount of white or black in the Color
True. Goes blacker Towards The Right
GPS receivers on the ground communicate with the GPS satellites to get continuous, accurate, all-weather world-wide, x-y and z positional information
True. User Segment.
Harmony
Two Adjacent Hues Basically next to each other
Constrast
Two Hues with One Hue Skipped in Between
Compiles all line features used to create a block layer for the entire country
U.S. Census Bureau
Started building a map infrastructure in the late 1970s and early 1980s
U.S. Census Bureau
GPS country of origin?
USA USA USA. Began 1978. since 1994. 31-32 number of satellites
Cartograms
Value by Area map Shows Land areas Sized to reflect The magnitude of The Variable being mapped
Interval data
Values are numerically ordered Interval difference is meaningful Examples are voltage potential and difference in concentration
What are The Two Common methods That Are Used?
Vector data Model and Raster data Model
Coverage
Vector data format introduced with ArcInfo in 1981 - Multiple physical files (12 or so) in a folder - Proprietary: no published specs & ArcInfo required for changes - Can be "exported" to a single E00 (E-zero-zero) file for transfer
Create base map
Vector features or raster images
Can improve accuracy to within 2 meters
WAAS
if you are going to compare with GPS data you have collected elsewhere in the world....
WGS84
National Program by USGS and USDA (NRCS). First cut is by automated. delineation from NED. Hand checked and edited
Watershed Boundary Dataset
When vertices are entered too close together, the GIS will remove some of them in order to reduce the file size
Weeding
Name three ways Digitizing software helps in assisting your digitizing errors
Weeding Snapping (Lines) Snapping (Nodes)
Definition of GIS
a computer based system to capture, store, manipulate, analyze, output, and distribute spatial data and information.
An electrical device with cross hairs and multiple buttons to perform data entry operations and an operator then enters the information using...
digitizing puck
is a hardened surface with a fine electrical wire grid under the surface.
digitizing tablet
One satellite range measurement. The receiver is positioned somewhere....
on the sphere defined by the satellite position and the range distance, r
What are the visible boundaries in TIGER census block groups?
• street • road • stream • Shoreline
Are shape files the most commonly used format?
Yes
Can Adjacent Colors be Used for Harmony?
Yes
Is it good Practice To Use mathematical progression or formula instead of picking arbitrary Values?
Yes
Does spatial data that has topology require additional data files that defines topology?
Yes.
Is topology the science and mathematics of geometric relationships?
Yes.
Are Map features smaller than blocks are the responsibility of local governments? What are the features?
Yes. - deeded land parcels - buildings - street curbs - parking lots
Is the Conceptual Model more Computer Oriented as it goes down levels? Is it Human Oriented at the 'Reality' (upper) level?
Yes. Yes.
Equal Intervals
_ Consistent widths -Easy To Understand _ Use equal width intervals with multiples of 2, 5, 10 0-100,100-200,200-300
Radio waves =
speed of light
Mapping Grade
1m-submeter $5,000-$10,000
The whole system of linked reference and subreference points came to be known as the datum
"ultimate reference point."
Travel Time Saved
$1.1 Billion Hours
Money Geospatial Saves Businesses
$1.4 Trillion
U.S. Industry Value
$73 Billion
Wages Paid Out
$90 Billion
Conic
(Albers Equal Area, Lambert Conformal Conic) - good for East-West land areas. Map looks like half eaten pizza
GIF
(Graphic Interchange Format): - .gif as its file extension. - Ideal for schematic drawings that have relatively large areas with solid color fill and few color variations. - Small file sizes
JPEG
(Joint Photographic Experts Group): - .jpg file extension. - Most widely used format for photographs and other images that have a lot of color variations - Uses file compression at the expense of picture detail, if you specify a lot of compression
Azimuthal
(Lambert Azimuthal Equal Area) - good for global views. This is the circle map.
NGVD29
(National Geodetic Vertical Datum of 1929)
NAD27
(North American Datum of 1927) uses the Clarke (1866) ellipsoid on a non geocentric axis of rotation
Define NAD27
(North American Datum, 1927)
Define NAD83
(North American Datum, 1983)
NAVD88
(North American Vertical Datum of 1988)
TIFF
(Tagged Image File Format) - .tif file extension - Very high quality images - Commonly used in publishing - Sizes are large because it is uncompressed
Cylindrical
(Transverse Mercator) - good for North-South land areas. Normal rectangular almost maps of the world
Define WGS84
(World Geodetic Survey, 1984)
WGS84
(World Geodetic System of 1984) uses GRS80, almost the same as NAD83
Main types of radiation processes in remote sensing
(i) reflection (ii) emission, (iii) emission- reflection
Floating Point
(number with a decimal point) in which case there is no VAT table, and simply one decimal value per cell
Define Coordinate Systems
(x,y,z) coordinate systems for map data
Get data from Continuously Operating Reference Stations (CORS) network
*Post-processed DGPS* - Designed to meet post-processing needs of GPS users - Works with the GPS data you collected out in the field, and adds
Vertical Photography
+- 3º vertical to Earth's surface Uses: • Planimetric base maps • Topographic maps • Raster digital elevation models • orthophotographs
UTM Coordinates
- (Easting, Northing) = (X,Y) - Expressed in meters: Northings (e.g. 4286289) and Eastings (e.g. 0525690) - Each integer equals 1 meter » Easting (walk 1m east, 0525690 > 0525691) » North (walk 1m north, 4286289 > 4286290)
Subdivision of a census tract
- 400 housing units, with a minimum of 250 and a maximum of 550 housing units
MS Access-based Personal Geodatabase
- > 8.0 GIS - Single-user editing, multiple read-only users - Stored as one .mdb (Access) file - Max 2GB total & 250,000 features per layer (effective max is 250-500MB)
File-based Geodatabase
- > 9.2 - Single-user editor, many read-only users - Faster and more efficient than personal gdb. - Unix and Microsoft supported - Max 1 TB (256 TB for raster)
Explain Scanning
- A document is scanned using a digital scanner. The document is typically fed through an opening in the front. - Light is emitted onto the document, and the reflected light is read in by a sensor. The sensor then records the reflected brightness to create an image.
Advantage of Satellite Based Datums
- A spheroid when used as a datum correctly maps the earth such that all Latitude/Longitude measurements from all maps created with that datum agree. - Rather than linking points through surface measurements, they are linked to reference point in outer space
Other sources of RS data
- Airborne (lidar, hyperspectral). - Unmanned (UAV). - Ground sensors
Limitations of UTM
- Although the distortions of the UTM system are small, they are too great for some accurate surveying. - Zone boundaries are also a problem in many applications, because they follow arbitrary lines of longitude rather than boundaries between jurisdictions.
What are some types of Vector Topology?
- Arc-node and node topology - Polygon topology - Route topology - Regions topology
Polygon Feature
- Area of homogeneous phenomena - In polygon layer the lines (arc) define areas
Statement of Problem (Remote Sensing)
- Identify Data to be collected -formulate Hypothesis
CAD Software
- Autodesk, AutoCAD (.dwg) - Bentley, Microstation (.dgn, .dxf)
Things to know about multiband rasters
- Band 1 is at bottom, Band 2 in the middle, Band 3 at the top. - Band represents a segment of the electromagnetic spectrum that has been collected by a sensor
Simple Raster
- Binary - 0-1 stored; feature present or not. B&W image - requires a different raster for each attribute (e.g. rock type) within a single theme (e.g. geology. Limestone>Sandstone>Mudstone = Geology)
What is TIGER?
- Census Bureau's product for digital mapping of the U.S. - Available for the entire U.S. and its possessions
What is TIGER?
- Census Bureau's product for digital mapping of the U.S. - Available for the entire U.S. and its possessions - Include the following geographic features • roads and street centerlines • railroads • rivers • lakes • census statistical boundaries
Spatial Analysis of Raster Data
- Conceptually simple, easy to implement - Well-suited for surface-and field-related phenomena (e.g. elevation, gravity, rainfall etc.) and for discrete features - Wide availability of data-sets; all remotely sensed data of this short - Best suited for "where" rather than "What" questions
Constructs Built from Raster Data
- Connected cells can be formed in to networks - Related cells can be grouped into neighborhoods or regions
What area does DOQQ cover?
- Cover an area measuring 3.75 minutes longitude by 3.75 minutes latitude, approximately 5 miles on each side
ArcInfo Coverages
- Created using ESRI's ArcInfo software - Older format - Set of files within a folder or directory called a workspace - Files represent different types of topology or feature types
How are features presented in a State Plane Coordinate System (UTM)?
- Defined for each State in the United States - East-West States (e.g. Texas) use Lambert Conformal Conic. - North-South States (e.g. California) use Transverse Mercator - Texas has five zones (North, North Central, Central, South Central, South) to give accurate representation - Greatest accuracy for local measurements
Define some concepts behind topology.
- Defines spatial relationships between features. - Each Arc has a beginning and ending node - Arc connects with other arcs at nodes. - Connected arcs that surround an area form polygons (this defines area and perimeter). - Arcs have a right and left side (this defines adjacency).
National Elevation Dataset. Go into detail.
- Digital Elevation Model with 1 arc-second (30m) cells - Seamless in 1° blocks for the United States - 10 billion data - Derived from USGS *1:24,000* quadrangle sheets
What are some features of Vector Arc Feature?
- Each Point has a unique feature - 2 points = line segment - >One line segment = arc - Endpoints of an arc are called nodes - Angle points = vertices - Two arcs meet at nodes
What are the three types of Geodatabases? And what is their main purpose?
- File - Personal - ArcSDE (Manage features and tables inside a database management system)
Rules of Data Table Formats
- First row must have attribute names with self-documenting labels (e.g. Pop5To17, Area) - Usual naming convention. first character is a letter. Remaining characters be any letters, digits, or the underscore character - All additional rows of a data table need to contain attribute values - None of the rows can be sums, averages, or other statistics of raw data rows
Advantages of RS
- Global view. - Multiscale observation. - Frequent observation. - Direct and non destructive observation. - Complete cover. - Non-visible spectral regions. - Height estimation
What are False Easting (False X) and False Northing (False Y)?
- In order to minimize distortion, most projections are centered in the mapping area. - The unfortunate side effect of this is that with the x/y origin in the mapping area, negative x or y values are likely. <To eliminate this possibility, False X and False Y values are chosen and added to all x and y values so that all x/y values are positive> <-- actual answer?
What ways does a Grid store data?
- Integer - Floating Point
Numeric Interval Classification
- Keep the number of intervals as Small as Possible _ Cut Points (break Points) points At which we choose To Break The Total attribute Range
What signals are added to improve functionality?
- L2C to ease GPS tracking for navigation - L5 for worldwide safety and life application - L5 for military application
How do you determine Latitude and Longitude?
- Latitude Φ 60 N - Longitude λ 20 E - Latitude is the angular distance between the plane of the equator and a line passing through the point under investigation and the center of the earth. - Longitude is the angular distance between the prime meridian and the meridian of the point under investigation
What are the three databases associated with GIS?
- MS Access-based Personal Geodatabase - File-based Geodatabase - SDE-based Geodatabase
What is the location reference system for Earth's surface?
- Meridians: lines of longitude - Parallels: lines of latitude - Prime meridian is at Greenwich, England (that is 0º longitude) - Equator is at 0º latitude
What exactly is Grace?
- NASA Mission launched in 2002 - Designed to measure gravity anomaly of the earth - Two satellites, 220 km apart, one leading, one trailing - Distance between them measured by microwave to 2µm - High gravity force pulls satellites together - Lower gravity force, lets them fly apart more - Gravity anomaly = difference from average
What is Raster Data Values consist of?
- Nominal (descriptive) - Ordinal (rank or order) - Interval/ratio (numeric items)
What are the types of data represented in cells?
- Nominal Data - Ordinal Data - Interval Data - Ratio Data
What is A Thematic map?
- Not meant to locate anything with Precision - Displays one or more Specific variables - Income, crime rate, disease, earthquake Center
In a Geodatabase the replacement for coverages have support for...
- Simple features: points, lines polygons - Complex features: real world entities modeled as objects with properties, behavior, rules, & relationships
Satellite Images
- large area coverage - broader spectral range - digital formats - inexpensive for large areas - geometrically accurate
SDE-based Geodatabase
- Personal (4), Workgroup (10) and Enterprise (??) versions - Multi-user simultaneous editing via versioning and long transactions - Uses standard db: ORACLE, SQL Server, etc - Attribute and spatial data in same database
Define point, line, area in a spaghetti data model.
- Point: recorded as a x,y coordinate pair - Line: series of x,y coordinates - Area: series of x,y coordinates. 1st and last coordinates are identical. closed loop polygon
Digitizing converts the features on the map into what three basic data types?
- Points: zero dimensional objects - Lines: one dimensional objects - Polygons: two dimensional objects
What does a Data Model Provide?
- Provides devs to make application domains that can be made into designs and then implemented - Users get a view of the structure of the system. Void from data of specific items and details of some applications.
Conceptual Model Levels.
- Reality - Conceptual Model - Logical Model - Physical Model
Limitation of Surface Based Datums
- Requires line of sight, so many survey points required - Errors compound with distance
What is A Reference Map?
- Road MAP or navigational map for air on Sea They give general Information - Cadastral Map shows property boundaries for The purpose of recording property Ownership for tax assessment - They provide accurate info about different-features
Steps in heads up digitizing
- Scanning the map - Registering the map - Digitizing the map
Name the three ways rasters can be drawn
Monochrome image Grayscale image Display colormap image
What are the four steps in the Remote Sensing Process?
- Statement of problem - Data Collection - Data to Info Conversion - Information Presentation
Personal Database
- Stores datasets in a Microsoft Access .mdb file - Storage sizes between 250 and 500 MB - Limited to 2GB - Only supported on Windows
File Database
- Stores datasets in a folder of files - Each dataset a file up to 1 TB in size - Can be used across platforms - Can be compressed and encrypted for read-only, secure use - ESRI's recommended choice
ArcSDE Database
- Stores datasets in a number of optional DBMSs: • IBM DB2, IBM Informix , Microsoft SQL Server , Oracle, or PostgreSQL - Unlimited size and users
What is a Georelational Vector Model
- Stores spatial and attribute data in separate files - The spatial data (geo) are stored in graphics files and the attribute files are stored in relational database - A georelational dataset uses a common field to link spatial and attribute data - Used for decades
What are the Three types of Digital file formats?
- TIFF - GIF - JPEG
Define The Ellipsoid Model
- The rotation of the earth generates a centrifugal force that causes the surface of the oceans to protrude more at the equator than at the poles - This causes the shape of the earth to be an ellipsoid, and not a sphere. -
What were the twofold needs by Census mapping?
- To assign census employees to areas of responsibility, covering the entire country and its possessions - To report and display census tabulations by area, officials determined that the smallest area needed for these purposes is a city block or its equivalent
What are some repositories for National/State/Global Data?
- U.S. Census - USGS and other government sources - GDT Dynamap/2000 U.S. Street Data - Engineering companies - land surveys, aerial photos, CAD drawings - University Web sites (e.g. Penn State's PASDA) - ESRI
What are some difference between Vector and Raster Data models?
- Unlike a vector structure, which stores coordinates explicitly, raster coordinates are contained in the ordering of the matrix - Raster datasets are defined by: - Origin in X,Y - Cell Size in X,Y - Angle of Y-Axis - Number of Cells in X and Y
Three Problems with CAD Drawings
- Use local drawing coordinates - Individual objects do not have unique identifiers - Focused on graphical representation of objects, and cannot store relationships
Define the Geoid Model
- Variation in the strength of the gravitational pull, cause regions to dip or bulge above or below a reference ellipsoid. - Geoid is the the three-dimensional surface along which the pull of gravity is a specified constant.
Shape File
- Vector data format introduced with ArcView in 1993 - Comprises several (at least 3) physical disk files (with extension of (.shp, .shx, .dbf), all of which must be present - Openly published specs so other vendors can create shape files
Satellite Based Datums
- With satellite measurements the center of the spheroid can be matched with the center of the earth.
What Are fields?
- Worth measuring at every point on The Planet - Radiation, Elevation, Temp, Soil Type & PH, Rainfall, Land Cover Type, and Ownership
Scanning the map (Heads Up)
- a user can scan the map at a high resolution
What are the four directly loadable data types?
- dBase (.dbf) - Text with comma (.csv) or tab-separated values (.txt) - Microsoft Access (.mdb) - Microsoft Excel (.xls)
Define fields
- each Variable has one value everywhere - Variable is A function of The Location - Basically geographic concept as a set of variables, with each Variable having A Value at every Location on The planet
Salaries for Remote Sensing Scientists And Technicians
Scientists: 27,000 in Employment and Growth By 10,100
Shape Files
- shp (stores feature geometry) - shx (stores index of features) - .dbf (stores attribute data) - .prj (projection data) - .xml (metadata) - .sbn and .sbx (stores additional indices)
What are Types of Thematic Maps?
-Dot Density MAP, Choropleth Map (Graduated Colors), Proportional Symbol MAP (Graduated Symbol), lsarithmic Maps, flow Maps, Cartograms
What are mental maps?
-Maps That exist only in our minds -does not reflect geographic reality but What is Our perception of the Location
When atom goes from one energy state to lower one, it emits an electromagnetic wave of characteristic frequency...
...known as "resonant frequency"
Survey Grade
0.1m $20,000
What are the four types of projected coordinate systems?
1. Conformal (true shapes) 2. Equal Area 3. Equidistant (true distances) 4. True Direction
In Situ Data Collection. Name the five methods used as source for GIS data.
1. Digitization of Historical Spatial Information 2. Global Positional System (GPS) 3. Traditional Land Surveying 4. Surveying Using a Total Station 5. In Situ Data Sampling or the Taking of a Census
How GPS works in five logical steps...
1. The basis of GPS is triangulation from satellites 2. GPS receiver measures distance (range) from satellite using the travel time of radio signals 3. To measure travel time, GPS needs very accurate timing (atomic clocks) 4. Along with distance, you need to know exactly where the satellites are in space. Satellite location. High orbits and careful monitoring are the secret 5. You must correct for any delays the signal experiences as it travels through the atmosphere (positional uncertainty)
How many characters can dBase field names contain?
10 Characters
In Selective Availability what is the distance in horizontal and vertical?
100m in horizontal and 160m in vertical
Return interval of each satellite
12 hour
How many orbital planes are the satellites on track of? How many on each?
6 orbital planes each containing 4 satellites
What is Hue?
A Basic Color such as Red, Blue, Green
Theodolite with an electronic distance measurement device, that can be used for leveling when set at the horizontal plane
A Total Station
"ultimate reference point."
A central location was chosen where the spheroid meets the earth: this point was intensively measured using pendulums, magnetometers, sextants, etc. to try to determine its precise location
Ratio Data
Data values measure a continuous phenomenon with a natural zero point Examples are rainfall and population
What is GIS?
A geographic information system (GIS) is a tool for making and using spatial information.
Planar Coordinate System
A planar coordinate system is defined by a pair of orthogonal (x,y) axes drawn through an origin
How does a projection start?
A projection starts with one of the three representations of Earth's irregular surface 1. Spheroid 2. Ellipsoid 3. Geoid
Display colormap image
A set of values is arbitrarily coded to match a defined set of red green blue values.
What are Maps built from?
Data. Shapes includes the geometry of the feature and where it is located on earth
Vertical Earth Datums
A vertical datum defines elevation, z
Where can one create a new feature class?
ArcCatalog. Then you can add spatial reference system. New fields
Coverage attribute table
Area and Perimeter
Conformal
At any point on the map the scale is same in every direction (USGS, 2011). Meridian and parallels interest at right angles
Oscillations of Atoms principle behind atomic clocks...
Atoms absorb or emit electomagnetic energy in discrete amounts that correspond to differences in energy between different configurations of the atoms.
What does each cell contain in a Raster Data Model?
Attribute value and location coordinates
Electromagnetic Spectrum
Bands often represent a portion of the spectrum. Ranges that vary from not visible to eye - the infrared or ultraviolet sections of the spectrum
How Can you differentiate graphic features?
By Using Opposite Colors
How Can you Normalize data?
By dividing one numeric attribute by another in order to minimize differences in values bused on The Size of areas or number of features in each area
How can you differentiate one graphic feature nicely?
By using colors that are equally Spaced
Limitations of Globes
Can we use globe in our hiking trip?
Three dimensional surface from which latitude, longitude and elevation are calculated
Datum
COMPASS
China. Initiated in 2000. being deployed. 35 by 2020.
Problems with Aerial Photography
Clouds, haze, shadows/sun angle, snow • Distortion - tip & tilt - relief distortion - radial distortion • Limited to 0.3 - 0.9 um (UV-NIR) • Storage and handling can be a problem
What are Three Geographic Data Models?
Conceptual Model- Set of Concepts That describe A Subject Mathematical Model- Model expressed in Symbols and equations Data Model - A Conceptual Model exp in A data structure
Isarithmic MAP
Contour Maps Maps continuous variables Uses lines Called isolines to connect places of equal quantity of The Variables Environmental Variables such as air quality, Temp, Precipitation, are considered Continuous (isotherms, isobaths. isohyets)
What are two file formats for Georelational Vector Data Model
Coverage Shape 'file'
Add Editor toolbar
Customize, Toolbars, Editor toolbar
WHAT term did The NSF Blue-ribbon Panel Introduce
Cyber Infrastructure
What were the Three Terms That were for This emerging field:
Cyberinfrastructure (Spatial CI), CyberGis, geographic information Science (Giscience) and Lately Spatial Information Systems
What are Event files?
Data table that includes map coordinates, such as latitude and longitude or projected coordinates
Nominal Data
Data values are categorized and have names. Data Value is an arbitrary type code. Examples are soil types and land use
Ordinal Data
Data values are categorized, have names, and the value is a numerical rank. Example is land sustainability classifications and soil drainage rank.
What does Vector Data Represent?
Discrete Features. Points. Lines. Polygons
Galileo Position System
EU and European Space Agency. Initiated 2005. Deployed. 18-24 satellites as of 2014
Monochrome image
Each cell has a value of 0 or 1. Often used for scanning maps with simple linework such as parcel maps which I have no idea what they are but I am very curious about but I am kind of stressed out about my four other exams so I couldn't really google it but I had the time to type all of this out. The last sentence was a run on sentence -10 points. College, huh? Go to college they said. Best four years of your life they said.
What is the Spaghetti Data Model?
Early vector data model to organize and manipulate line data.
Start editing
Editor, Start editing
Salaries GIS Scientists
Employment (2008) 209,000 and Growth By 72,600 with Expected Growth Rate By A to 13
Dichromatic Color Scale
Exception To The Typical Mono Scale. This is A Combo of two Mono Scales with a low color value in Center. Uses Natural midpoint which is a zero
Converting the image to a paper or other hardcopy form would not likely introduce error
False. Converting the image to a paper or other hardcopy form would likely introduce error (advantage of heads up digitizing)
GPS receivers are composed of an antenna, a central processing unit and a relatively inexpensive carbon infused metallic colored clock
False. GPS receivers are composed of an antenna, a central processing unit and a relatively inexpensive clock
Laser range finder can be accurate to a few millimeters at 10,000 m
False. Laser range finder can be accurate to a few millimeters at 1,000 m
Longitudinal strips extend from 90 degrees South latitude to 94 degrees North latitude.
False. Longitudinal strips extend from 80 degrees South latitude to 84 degrees North latitude.
Positions based on carrier signal measurements (L1, L2, and L5) frequencies are more less accurate than those based on the code
False. Positions based on carrier signal measurements (L1, L2, and L5) frequencies are *more* accurate than those based on the code
Snapping does occur if the nodes and/or lines are separated by more than the snap tolerance
False. Snapping does NOT occur if the nodes and/or lines are separated by more than the snap tolerance
on-screen digitizing may NOT be used to limit operator-induced positional error when digitizing.
False. on-screen digitizing may be used to limit operator-induced positional error when digitizing.
Along with distance, you don't need to know exactly where the satellites are in space. Satellite location. High orbits and careful monitoring are the secret
False. Along with distance, you need to know exactly where the satellites are in space. Satellite location. High orbits and careful monitoring are the secret
To measure travel time, GPS doesn't very accurate timing (atomic clocks)
False. It needs them
....satellites required to solve for x, y, z, and t
Four
Growth In GIS Related Markets
GIS(9.60), Gnss Base(22%), LIDAR(16.64), Gis Market in BFSI(4.95), Utilities(10.37), farming(13.36)
L1 (1573.42 MHz) and L2 (1227.6 MHz)
GPS satellites broadcast two carrier signals
GSDI
Global Spatial Data Infrastructure Association (GSDI)was established to coordinate collection and processing of GIS data worldwide
Disadvantages of OpenStreetMap
Good source of data but for some areas quality documentation and uniformity may be lacking
Why Do GIS?
Government decisions are based around geography. $270 Billion Market in 2013 Six New Occupations
Choropleth Map
Graduated Colors Shows rate, percentages of ratio or phenomenon Each geographic unit recieves A color pattern Color coded polygon Maps Uses monochromatic Scales or saturated colors
Proportional Symbol Map
Graduated Symbol Shows relative or absolute size of the entity to be mapped or number of particular phenomenon Located at that point if you want to show relative amounts, sizes or degrees of importance at specific Location
Graphic Scale
Graphic Representation of A map Scale Places A line on the map with ground dist marked such as 10,15 miles
WHAT IS GRACE?
Gravity Recovery and Climate Experiment
An imaginary circle drawn in any direction around the Earth's surface and whose plane passes through the center of Earth
Great Circles
Associated with plant photosynthetic activity, biomass, fractional cover of vegetation
Greenness
measure hundreds of wavelength bands
Hyperspectral - "HyMap" airplane sensor has 126 bands - Ocean Optics has thousands of bands
Incident Light
I = R + A + T I, R, A, and T are usually written as energy per unit time
Equal Area
If every part of the map , as well as the whole, has the same area as the corresponding part on the Earth, at the same reduced scale.
Information Presenetation (Remote Sensing)
Image Metadata (sources and processing lineage) Accuracy Assessment (Geometric, Thematic, Change detection) Analog and Digital Stats and Graphs
What is a Raster Model?
Implementation of field conceptual models. Array of cells that represents objects.
Data Collection (Remote Sensing)
In Situ Measurements (field (GPS), LAB (reflectance)) Collateral Data (Digital elevation model's, Soils, geology, population) Remote Sensing
What did They Realise About The future
In The future Science and Engineering will focus Heavily on huge datasets and will need digital data, grid's AND Software tools
Selective Availability
Intentional degradation of GPS accuracy
...the satellite signal slows as it passes through the atmosphere. The GPS system uses a built-in model that calculates an average amount of delay to partially correct for this type of error. Any error due to this is usually negligible
Ionospheric and Atmospheric Delay
What is Vector Point Feature?
It is a point layer which is a collection of records with (x,y) coordinates
What Are Atoms of Geographic Information?
It's An Infinite number anol We Can give A two Word description of every Sq km On The planet, 10 GB 1 number = Every Sqkm = I Pb (trillion Bytes)
QZSS.
Japan. 2002 initiation. Being deployed. 1st satellite in 2010
What codes do L1 and L2 carry?
L1 carries both C/A and P code L2 carries only P code
Spatial Questions Asked by GIS
Law Enforcement, Developer, University admissions, Aid worker, Realtor, Delivery Truck, Legislator, CDC
Light Vs DARK Colors
Light = Low Values DARK Colors = High Values Human eye 😲 Dark Colors
What are the two systems associated with Network Data Model?
Linear Referencing System Dynamic Segmentation
Increasing Interval Width
Long Tailed distributions 0-15, 5-15, 15-35
What are MXD files?
MXD files are Project files Saves your Layout, Preferences, Data not included, . mxd extension
Thematic Mapping
Map Types = Mental and Tangible Tangible = Reference and Thematic and Virtual Thematic = Qualitative and Quantitative Quantitative = Single Variable and Multi-Variable
When was Selective Availability turned off?
May 2, 2000
What Scale Would 1:100,000 be Considered?
Medium Scale
What is A DATA Model?
Method Used to represent real world objects
Active Remote Sensing
Microwave (RADAR) Laser (LIDAR) Acoustic (SONAR) Illumination provided by the sensor system (light or radiowaves)
GLONASS
Mother Russia. Initiated 1976. Restoration. 23-24 satellites in 2011
measure several wavelength bands
Multispectral - Average reflectance in the bands - Landsat TM-7 had 7 bands - NDVI: bands 3 (red) and 4 (NIR)
USGS Topo maps are...
NAD27
if you are in N. America, and want to match your... topo maps
NAD27
if you are in N. America, and are collecting raw data...
NAD83
...takes advantage of the ability of vegetation to strongly reflect near-IR and poorly reflect red, resulting in a high contrast between bands and a high...
NDVI
NDVI FORMULA
NDVI = (NIR - RED)/(NIR+RED)
Is making geographic data more accessible to the public by reducing duplications, improve quality and reduce costs
National Spatial Data Infrastructure (NSDI)
What is a Network Data Model?
Network topological relationships define how lines connect with each other at nodes and define rules about how flows can move through the network
Can Representations be Accurate all The Time?
No Representations Can be deceiving.
Can geometric characteristics of features that have topology be changed?
No. Even when the data maybe altered through projection and data transformation
NDVI
Normalized Difference Vegetation Index
what Are Objects?
Objects Are Well defined boundaries in An empty Space. Example could be the 49 Houses in A Subdivision
The Geographic Coordinate System
Once you have a ellipsoid, you also define the location of poles (axis points of revolution) and equator (midway circle between poles, spanning the widest dimension of the spheroid), - You have enough information to create a coordinate grid or "graticule" for referencing the position of features on the spheroid.
Variables In Thematic Maps
One Variable = univariate maps Two Variables = bivariate Maps
What are the four types of Database Relationships?
One to one One to many Many to one Many to many
Extended Raster
One value per cell but multiple attributes per value in value attribute table (VAT) --> what does this mean? In the VAT table there is a limestone which has the value of 1 but there are 7 Limestones in total in the Raster Data Model.
An effort to develop global data through international volunteer collaboration
OpenStreetMap
CLASH
Opposites
....these are inaccuracies of the satellite's reported location. Any error due to this is usually negligible.
Orbital errors: AKA ephemeris errors
Digital imagery in which distortion from the camera angle and topography have been removed, thus equalizing the distances represented on the image
Orthophotography
French scientists suggested earth was flattened at equatorial regions
Oui. Vrai. True.
What does Vector topology help with?
Overshoots Slivers Dangles Not Sharing borders
Passive Remote Sensing
Panchromatic Multispectral Hyperspectral • Illumination typically by the sun • Passive - no energy provided by the remote sensing system to the object example the moon or the earth from space
What are the two types of Remote Sensing?
Passive Active
What are some components of a Vector Model?
Point, line, and polygon representations. Used in Cartography and network analysis.
Exponential Scale
Popular method of Increasing intervals Break values That Are Power of 2n and 3n mostly Start W/T Zero 0, 1-2, 3-4, 5-8, 9-16
Describes sensitivity of receiver to changes in the geometric positioning of the GPS satellites
Position Dilution of Precision (PDOP)
This is the ratio of the volume of a tetrahedron created by four observed satellites to the volume defined by ideal tetrahedron
Position Dilution of Precision (PDOP)
(PDOP)
Positional Dilution of Precision Satellite position/geometry. - Describes sensitivity of receiver to changes in the geometric positioning of the GPS satellites - This is the ratio of the volume of a tetrahedron created by four observed satellites to the volume defined by ideal tetrahedron
What is A Color wheel?
Provides Guidance in choosing Colors
Quantitative Vs Qualitative thematic Maps
Qualitative maps are nominal which means It's Textual and not numerical Quantitative maps are numerical meaning The data is in numbers and was measured
Range formula
Range = speed of light X travel time
What does Raster Data form?
Raster Data forms a grid of cells or pixels
Diagrams of Raster and Vector data
Raster data is described by A Cell grid, one Value per cell
- Clocks similar to quartz watch - Always an error between satellite and receiver clocks ( t)
Receiver Clocks
.....A GPS receiver's built-in clock is not as accurate as the atomic clocks onboard the GPS satellites. Leads to slight timing errors. Any error due to this is usually negligible.
Receiver clock errors
Name three types of GPS Units
Recreational Grade Mapping Grade Survey Grade
Red-Green-Blue Composite
Red in the top half Green the Left half Blue in the bottom half
- 2 Cesium & 2 Rubidium in each GPS satellite - $100,000-$500,000 each
Satellite Clocks
Raster data Model
Regular grid of Cells Each Cell represents an area on the ground Spatial Resolution, Value assigned to cell represent reflectance, land Cover, Elevation Sateillite images, DE-M, and They are good for continuously changing attributes
measures electromagnetic energy reflected or emitted from objects - airborne or satellite based instruments
Remote Sensing
Dot Density MAP
Show Variation in Spatial density of Some Phenomenon. Used To plot The Absolute number of things. Thematic Maps Can be Used To plot one or more Specific Variables.
Equidisdant
Show true distances along center of the projection or along a special set of lines
Flow Maps
Shows Volume and directions of The movements of Something Such as population or commodities
Pythagoras and Aristotle reasoned the Earth was a sphere
Si. Yes. True.
...this occurs when the GPS signal is reflected off objects such as tall buildings or large rock surfaces before it reaches the receiver. This increases the travel time of the signal, thereby causing error
Signal multi-path
Instruments and Procedures used for millenia i.e. Egypt, Cyclopedia
Simple plane-table instruments and procedures
Takes nodes and snaps them to a nearby line, if the nearby line is within a specified tolerance
Snapping (lines)
Snaps nodes to nearby nodes within a tolerance.
Snapping (nodes)
Sources of Signal Interference
Solid Structure Electromagnetic fields
In a Raster Data Model what does spatial data model define?
Space as an array of equally sized cells arranged in rows and columns, and composed of single or multiple bands.
Dynamic segmentation
Special case of linear referencing in which data values are added dynamically to the route each time the user queries the database
How are stations measured in a triangulation survey network?
Stations may be measured using astronomical (open circles) or surface surveys (filled circles)
What is a geodatabase?
Store for all types of geospatial information
Starting points need to be very central relative to landmass being measured
Surface Based Datums
Prior to satellites, datums were realized by connected series of ground-measured survey monuments
Surface-Based Datums
What do Layer files Save?
Symbology and Setting Used to Saving Legend Setting extension is .|yr
WAAS needs unobstructed view of the horizon!
TRUE
A Quartile is A distribution That Seperates in to equal Sizes of feature Attribute
TRUE. 0-25, 25-50, 50-75
Requires a person to enter coordinate information through the use of a digitizing tablet and digitizing puck
Tablet Digitizing Answer is literally in the question. Kind of.
The United States Geological Survey (USGS) has combined data from 20 federal agencies and created a base map at a single portal
The National Atlas
This is described as "cornerstone" of U.S. mapping efforts
The U. S. National Map
What is the difference between the ellipsoidal and Geoidal height?
The difference between the ellipsoidal height and geoidal height at any location is less than 100 meters over most of the Earth
Define Contrast
The greater the difference in value between an object and its background is greater The Contrast
DOQQ image resolutions
The ground length of one pixel of the image - image with one meter resolution means that each pixel in the image represents one square meter on the ground.
How do you convert to Degrees from Degrees: Minutes: Seconds?
The latitude and longitude are input in degrees, so you might need to convert to decimal degrees from degrees: minutes: seconds EXAMPLE: 65:45:36 south latitude converts to -(65 degrees + 45 minutes x (1 degree/60 minutes) + 36 seconds x (1 minute/60 seconds) x (1 degree/60 minutes) = -65.76 degrees latitude
Linear Referencing Systems
The locations of geographic entities are stored as distances along a network from a point of origin
In most cases preserving one of these spatial properties of the data decreases accuracy of the other properties (projected coordinate system)
True
Define Map Projections
The transformation of a curved Earth to a flat map.
Digitizing the map (Heads Up)
The user can zoom to specific areas on screen and trace points, lines, or polygons on the map. Because the maps are already in the correct geographic coordinate system anything digitized on top of the map will also be in the correct coordinate system.
Route topology
The way that a line feature of one type (e.g. commuter rail line) shares segments with line features of another type (e.g. Amtrack rail line)
Arc-node and node topology
The way that line features connect to point features
Regions topology
The way that polygons overlap (e.g. GIS layers with a time component) or when spatially separate polygons are part of the same feature
Is a geometric deformation indicator. A small circle on the surface of Earth projected as a small ellipse on a map projection plane.
Tissot's Indicatrix
TIGER
Topologically Integrated Geographic Encoding and Referencing files
EarthCube Vision
Transform The Conoluct of Geosciences Reasearch. Predict Earth System from center of The sun to the Center of Earth Earth Cube integration of geosciences data, information, Knowledge. and Tools
Name Some Data Types.
Triangulated Irregular Network, Annotation, Multipatch
1:5,000 is A Large Scale
True
1:50,000,000 is A Small Scale
True
A CAD system is real-world entities are represented symbolically as simple point, polyline, and polygon vectors
True
A Vector Model is an implementation of discrete object conceptual model
True
A cartesian coordinate system is one that assigns two coordinates (x & y) to every point on a flat surface.
True
A conventional total station needs local or federal control points
True
A projected coordinate system is always based on a geographic coordinate system that is based on a sphere or spheroid.
True
A raster can have one or many bands
True
All satellites transmit same signal "string" at same tim
True
An advantage of heads up digitizing is many data sources are inherently digital, these data may be magnified on screen to any desired scale
True
Another OpenStreetMap drawback, method of distribution data is available in publicly defined but rarely used format, and a 3rd party sales the data in standard format
True
As plants grow, canopy and biomass increase
True
Atom Clock came into being during World War II; nothing to do with GPS. Physicists wanted to test Einstein's ideas about gravity and time
True
Babylonians believed the Earth was flat disk floating in an endless ocean
True
Can DATA frames be Used for Context?
True
Carrier signals are modulated to produce coded signals C/A code at 1.023 MHz and the P code at 10.23 MHz
True
Datum allows us to figure out where things actually are on the graticule since the graticule only gives us a framework for measuring, and not the actual locations
True
Datum is a frame of reference for placing specific locations at specific points on the spheroid
True
Digitizing software allows a user to collect data in point mode or stream mode.
True
Einstein predicted that clock on Mt. Everest would run 30 millionths of a second faster than clock at sea level
True
Elevation is typically defined as the distance above a geoid.
True
French Royal Academy of sciences between 1730-1745 measured the shape of earth near Equator in South America and in high northern latitudes in Europe
True
GPS clocks are cesium clocks
True
GPS receiver measures distance (range) from satellite using the travel time of radio signals
True
GRID's are a raster data format
True
Geoid is always at right angles to the direction of local gravity, and this surface is the reference against which heights are measured
True
Global data sets are less common than national data set
True
Green leaves absorb more red and blue light
True
Groups of cells that share the same value represent the same type of geographic feature.
True
Heights above an ellipsoid are often referred to as ellipsoidal height.
True
Horizontal Earth Datums. An earth datum is defined by an ellipse and an axis of rotation
True
Ideally plane-table was placed directly over a monument that had x, y, z coordinates.
True
In GCS, Each degree of latitude represents about 110 km, although, that varies slightly because the Earth is not a perfect sphere
True
In GPS Standardization it is better to use UTM coordinates than Latitude and Longitude
True
In Line (Arc) Feature each point has a unique location
True
In Polygon feature line segments bound the feature.
True
In Polygon feature the first and last coordinates pairs are in the same location
True
In a projected coordinate system, locations are identified by x,y coordinates on a grid, with the origin at the center of the grid.
True
In order to use the Vector Data in ArcMap, the coordinate system for the data must be identified
True
What are UTM's used in?
USGS topographic map, and digital elevation models (DEMs)
Conformal projection, so small features appear with the correct shape and scale is the same in all directions. (all distances, directions, shapes, and areas are reasonably accurate ).
Universal Transverse Mercator (UTM)
Map Ratios
Use of with any Linear measurement Unit Such as ft. miles, meters Example: 1:24,000 Which means I inch on The map is 24,000 inches on The ground
Three segments of GPS
User Satellite Control
Surface Based Datums were largely done without having to measure distances. How?
Using high-quality celestial observations and distance measurements for the first two observations, could then use trigonometry to determine distances
Registering the map (Heads Up)
Using the same transformation methods previously discussed, the user can enter control points on screen and transform the scanned image to real world coordinates.
25 ground reference stations positioned across the U.S. Send data to 2 master stations
Wide Area Augmentation System (WAAS)
Point mode
allows the operator to place discreet points to represent geographic objects. This is the method you are probably most familiar with
Stream mode
automatically places points at specified time intervals, and the user traces the digitizing puck along the geographic features.
Resonant frequencies are identical for every atom of a given type...
cesium 133 atoms: 9,192,631,770 cycles/second
Two satellites the receiver is somewhere on a....
circle where two spheres meet
Why is choosing the right projection important?
controlling distortions
Reflectance
defined as the ratio of reflected light to incident light p=R/I
Transmittance
defined as the ratio of transmitted light to incident light t=T/I
Grayscale Image
each cell has a value of 0 to 225. Used for black and white aerial photographs
Add new feature class
example would be streets.
Flattening Ratio Formula
f = (a-b)/a
Ellipsoidal Height formula
h = H + N h = ellipsoidal height H = orthometric height N = geoidal height
What two things are needed for a Datum?
spheroid and set of surveyed and measured points
Problems with Infinite Complexity
many Limiting details, User must make A choice, Devs must allow for many options Important Question is what we Choose to Think About The World
What is taken into account in a Vertical Earth Datum?
map of gravity anomalies between the ellipsoid and the geoid
What is topology?
mathematical study of the properties of objects.
Is the The Spherical Model accurate?
model is very inaccurate and should only be used for scales smaller than 1:5,000,000,000.
Three satellites the receiver is at...
one of two points where the three spheres intersect
Four satellites the receiver is at...
one point where the spheres intersect
When digital data for a GIS project is not available, it is created from....
paper maps
Early twentieth century Bridseye and Clarke from USGS, used ____________ in western USA
plane-table surveying
C/A, P and M are commonly referred as...
pseudo-random code
Specialized software is used to convert the scanned image into lines. This process is called....
raster to vector conversion (R2V)
Absorbtance
ratio of absorbed light to incident light a=A/I
Receivers decodes each signal from GPS satellite to identify...
satellite, transmission time and satellite position at the time the signal was sent
HIGH PDOP...
satellites close together. Large area of uncertainty
LOW PDOP...
satellites widely spaced small area of uncertainty
What do Datum's define?
the origin and orientation of latitude and longitude lines.
Define Geodesy
the science of measuring the shape of the Earth
NAD83
uses the GRS80 ellipsoid on a geocentric axis of rotation
Define Map Projection
the transformation of a curved Earth to a flat map
Polygon topology
the way that neighboring polygons connect and share borders
Receivers have nanosecond accuracy (0.000000001 second)
true
the Greenwich Meridian is the origin of the X axis and the Equator is the origin of the Y axis
true
How did Eratosthenes measure the circumference of the earth?
used a deep well in Syene, Egypt and vertical post at Alexandria at an angle 7 12' and found circumference of Earth, 40, 250 km, he was off by 4%, 38,762 KM
How Can We Limit The Detail On Maps?
we Can aggregate, generalize, approximate. Can We ignore The water? But That is 2/3 of The map. You Can give one Temperature To Houston for ex. Sample The Space As do measurements only in Weather stations in Weather stations. Nearly All geographic data miss detail.
How many satellites orbit the Earth? And at what speed?
~31-32 satellites, orbit the Earth at 20, 200 km\12,600 mi
Where and what do the two master stations do in regards to WAAS?
• 2 master stations (on west and east coasts) - Accounts for satellite orbit, clock drift, and signal delays - Sends corrections to geo-synchronous equatorial satellites, which is received by your GPS unit
Smart Station Procedure
• A SmartStation uses a GPS-enabled station that uses dual frequency GNSS receivers and real-time kinematics (RTK) technology. • A SmartPole is a GPS enabled stadia rod. Both SmartStation and SmartPole can be used independently to acquire accurate x, y, z, measurements • A surveyor will setup the SmartStation at a location that has unobstructed view of the sky. The surveyor then takes the SmartPole and walks to important locations in the terrain to obtain measurements *make sure to look at image in lecture explaining this process*
Explain Datum's in every way possible.
• A datum is essentially the model that is used to translate a spheroid into locations on the earth • A spheroid only gives you a shape—a datum gives you locations of specific places on that shape. • Hence, a different datum is generally used for each spheroid
Five steps involved in Digitizing new features
• Create base map • Add feature in ArcMap • Start editing (Editor toolbar) • Digitize feature • Stop editing and save
What are the two types of Coordinate Systems?
• Geographic coordinates (Φ, h, z) Latitude and Longitude. • Projected coordinates (x, y, z) on a local area of the earth's surface
Explain the procedure involved in Traditional Land Surveying
• Ideally plane-table was placed directly over a monument that had x, y, z coordinates. • Surveyors repeated this procedure at second stations and measured the distance between stations • As second member of the surveying crew would go to a station 3 and hold a leveling rod (stadia), the surveyor at home station could view the stadia through alidade and determine the change in elevation
Certain features of a Geographic Coordinate System
• Like a planar coordinate system, with an origin at the point where the equator meets the prime meridian • The difference is that it is not a Grid because grid lines must meet at right angles; this is why it's called a graticule instead
What are the four sources to get Soil Data?
• Natural Resources Conservation Service (NRCS) • National Cartography and Geospatial Center (NCGC) • State Soil Geographic Database-STASGO • Soil Survey Geographic Database- SURGO
What are Representations?
• Needed To Convey Information ° fit Info into a standard form or model • Simplify Representation
Ways of Measuring Spectral Reflectance
• Optical Spectrometer • Non-imaging - Just spectrum • Ground-based, aircraft, or satellite • Example: Ocean Optics Spectrometer - 350 to 1,000 nm
Four Basic Functions of GPS
• Position and coordinates. • The distance and direction between any two waypoints, or a position and a waypoint. • Travel progress reports. • Accurate time measurement.
What are some Analysis Examples?
• Predict fate of pollutants in the atmosphere • The spread of disease • Animal migrations • Crop yields • EPA - hazard analysis of urban superfund sites • Local to global scale forest growth analysis
- Incorporates the L2 satellite signal real-time - Need special DGPS equipment
• Real-time DGPS
Two types of Differential GPS (DGPS)
• Real-time DGPS • Post-processed DGPS
NHDPlus Reach Attributes
• Slope • Elevation • Mean annual flow - Corresponding velocity • Drainage area • % of upstream drainage area in different land uses • Stream order
Name three methods of Digitizing.
• Tablet Digitizing • Heads-up Digitizing • Scanning and Vectorization
Steps for heads down digitizing
• Tape map to the digitizer • Register control points on the map • Estimate two conversion equations (one for vertical and one for horizontal coordinates) • Digitize vectors (points, lines, or polygons)
Applications of GPS
• To determine exact location • Routing • Navigation • Finding Places • Precision agriculture • Geotaging • Crowd sourcing • Geological
Types of Air Photos
• Vertical • High Oblique (horizon) & Low Oblique (no horizon) • Stereo/3D
Differential Correction Procedures
• WAAS (can improve to 2-5m) • DGPS (can improve to 0.1-1m) • Real-Time Differential Positioning • Real Time Kinematic and Virtual Reference Stations
Where do Representations occur?
• We get Info Through Our senses and Store it in our minds • In photographs, 2-dimensional models of Light received by the camera • In Text, Info is in words
Aerial Photographs
• common • relatively inexpensive • easy to interpret • small area coverage • can be geometrically corrected
Non-visible boundaries in TIGER?
• county, city, neighborhood boundary • property line
What features are included in TIGER?
• roads and street centerlines • railroads • rivers • lakes • census statistical boundaries