GEOG 201 Midterm
GNSS
the global navigation satellite system, an overall term for the technologies that use signals from satellites to find locations on Earth's surface.
equator
the line of latitude that runs around the center of Earth and serves as the 0 degree line from which to make latitude measurements.
prime meridian
the line of longitude that runs through Greenwich, England, and serves as the 0 degree line of longitude from with to base measurements.
attributes
the non-spatial data that can be associated with a spatial location (i.e. house value, house address, name of the owner, number of household residents, etc) There are 4 types: nominal data, ordinal, interval, or ratio data
PDOP
the position dilution of precision; descries the amount of error due to the geometric position of the GPS satellite.
projection
the translation of locations on the 3D earth to a 2D surface (map)
two tables may be joined together if what condition is met?
the two tables have a common field
Summarize the three basic systems and tools that make up geospatial technology.
(1) geographic information systems (GIS) - computer based mapping, analysis, and retrieval of location-based data (2) remote sensing - acquisition of data and imagery from the use of satellites or aircraft (3) global positioning system (GPS) - acquisition of real-time location information from a series of satellites in Earth's orbit
Define the four different types of non-spatial (attribute) data that are linked to spatial (locational) data
(1) nominal data is a unique identifier of some kind - if numerical, the differences between numbers are not significant, (2) ordinal data refers solely to a raking of some kind (1st, 2nd, 3rd, etc), (3) interval data is numerical data where the difference between numbers is significant, but there is no fixed non-arbitrary zero point associated with the data, and (4) ratio data is numerical data where the difference between numbers is significant, and there is a fixed non-arbitrary zero point associated with the data
Describe how datums and the geographic coordinate system of latitude and longitude are used to reference locations on the Earth's 3D surface
when a geographic coordinate system is overlaid onto a datum, the latitude and longitude values are systematically used to reference specific points on the Earth's surface.
Describe how and what kind of delays in the travel time of the satellite signal can cause errors in the calculation of a GPS location.
(1) selective availability is intentionally introduced error by the US into GPS with the goal of protecting the military from enemy forces. this introduced error in both the timing information (delta error) and in the satellite ephemeris info (epsilon error) resulting in an accuracy of about 100m. selective availability was turned off by US government in 2000. (2) multipath error introduces additional delays into the reception of signals due to reflecting from surfaces before reaching the receiver. - one method of improving accuracy is the DGPS method using ground-based correction in addition to the satellite signals.
Summarize the basic components of NAVSTAR GPS
(1) the space segment is made up of numerous GPS satellites orbiting Earth in fixed paths, the (2) control segment is a series of worldwide ground stations that track and monitor the signals being transmitted by the satellites, and the (3) user segment represents the GPS unit somewhere on the Earth that is receiving satellite signals.
GIS
(geographic information system) computer-based mapping, analysis, and retrieval of location-based data
GPS
(global positioning system) a technology using signals broadcast from satellites for navigation and position determination on Earth.
GPS
(global positioning system) acquisition of real-time location information from a series of satellites in Earth's orbit
NLCD
(national land cover database) a raster-based GIS data set that maps the land-cover types for the entire US as 30m resolution, wherein each grid cell is coded with a value that corresponds to a specific land cover type at that location (i.e. open water, developed, deciduous forest, etc)
UTM
(universal transverse mercator) the grid system of locating coordinates across the globe. divides the world into a series of zones, and then determine the x and y coordinates for a location in that zone.
WAAS
(wide area augmentation system) a satellite-based augmentation system that covers the US and other portions of North America. helps to obtain more accurate position information for aircraft and has developed widespread uses beyond the world of aviation.
use of WAAS can reduce position error to within
3 meters
Datum
A reference surface, or model of Earth that is used fro plotting locations anywhere on the actual surface of Earth. The datum represents the size and shape of the Earth which, contrary to popular belief, isn't perfectly round.
which of the following is an example of non-spatial data A. list of addresses for a delivery truck to visit B. parcel database of all residential developments in a neighborhood C. digital map of all roads in a township D. map of locations of emergency phones on a college campus
A. list of addresses for a delivery truck to visist
environmental conditions for the planet earth can be monitored by which of the following A. remote sensing B. Global Positioning System C. tabular databases D. Global Satellite Program
A. remote sensing
Which of the following is not an example of goespatial data? A. the length of a piece of wood B. the measurement made between two road intersections C. the size and shape of the continent of North America D. the dimension of a lake
A. the length of a piece of wood
Explain how the resolution of a grid cell relates to the distance and area on the Earth's surface in the raster data model.
As resolution increases, the area that each grid cell represents of earth's surface decreases as does the distance between grid cells. When resolution decreases, the grid cells become larger representing a greater area and larger distances between grid cells.
the Master Control station for the US GPS is located in
Colorado
the chinese counterpart of GPS is
Compass
The series of ground stations that help maintain GPS refers to which component of GPS?
Control Segment
Explain the formula for calculating distance from GPS receiver to satellite
D = (time traveled)*(constant speed of light) the signal is sent at the speed of light from the satellite to the receiver. multiplying the velocity of the signal by the time traveled gives the distance traveled.
the use of a base station or other earth-bound source to transmit a correction signal to a GPS receiver refers to
DGPS
Describe how spatial data are projected onto a 2D flat developable surface of a cylinder, cone or flat plane.
Depending on the area of the earth that is being mapped, the Earth's spherical surface will be projected onto a 2D map surface. this is done using a cylinder, cone, or flat plane. These 2D representations always have some sort of distortion built into them, simply because they're 2D versions of a 3D reality. The Lambert Conformal Conic is used for cone projections, and the Transverse Mercator is used for cylindrical projections
Describe how GIS allows the user to store and link spatial (locational) data to non-spatial (attribute) data.
Each layer in the GIS has an associated attribute table that stores additional information about the features making up that layer. The attribute table is like a spreadsheet where objects are stored as records (rows) which are the locations and the information associated with the records - the attributes - is stored as fields (columns).
Describe why geospatial technologies can be considered 'geography in action'.
For example, if you use an in-car navigation system to go somewhere new, you're using basic geographic concepts of space and place through technology.
computer-based mapping and analysis of location-based data best describes
GIS
the overall term for the technologies that use signals from satellites to find locations on earth's surface is
GNSS
the European equivalent of GPS is
Galileo
Describe how the disciple of geography is fundamental to understanding geospatial technology?
Geography is the study of the Earth's surface as the space within which the human population lives, essentially not just the study of where things are, but also why things are where they are. GIS has been described as 'geography in action', for example, if you use an in-car navigation system to go somewhere new, you're using basic geographic concepts of space and place through technology.
acquiring real-time location information from a series of satellites in orbit best describes
Global positioning system
Describe how the WGS84 and NAD27 datums are created differently, and explain the implications of those differences for finding your location on Earth.
NAD27: developed for measurements of the US and North America. it has a center at Meades Ranch in Kansas WGS84: developed by the US Department of Defense, and is used by the GPS for locating points worldwide on Earth's surface. measurements made with one datum don't necessarily line up with measurements made from another datum. a datum transformation is required to alter the measurements from one datum to another.
describe how SQL allows the user to create a subset of geospatial data based on specific queries of the non-spatial attribute data
SQL is a specific format that is used for querying, or retrieve data from a database based on certain conditions, a layer or database to find what attributes meet certain conditions. Attributes can be sorted and selected from relational or boolean operators.
What makes geospatial data unique?
The ability to assign a location to data is what makes geospatial technology different from other systems. Knowing where something is located from the data.
Geoid
The actual shape of Earth, since it isn't a smoothed ellipsoid. Gravitational forces affect different parts of Earth in different ways. causing some areas to be out of sync with the ellipsoid. A geoid places the surface of the Earth at mean sea level to try to account for these differences.
Ellipsoid
The actual shape of the Earth. It's larger at its center than it is at its poles.
summarize the difference between the discrete object view (vector data model) and the continuous field view (raster data model) of locations in the real world
The vector data model represents real-world spatial information as a series of vector objects, items realized in the GIS as points, lines or polygons. The continuous field view is a conceptualization in which all items vary across Earth's surface as constant fields, and values are available at all locations along the field.
spatial query
the conditions used to retrieve data from a database, a way to select only those records from the attribute table that reflect the qualities/objects you want to work with
Explain the concept of trilateration and why 4 satellites are needed to determine an accurate position on the Earth's surface.
Trilateration is the process of using three points of reference to find where you are on the Earth's surface. (for example how geologists find the epicenter of earthquakes on the earth's surface from info from 3 seismographs) 3D trilateration finds a point on the Earth's surface using spherical distances rather than flat circular distances. Four satellites are necessary in 3D trilateration to locate one position on earth's surface because the spheres from just 3 satellites have 2 intersection points where the GPS could be located. Usually one of the two points is in outer space and can be disregarded, but to just have one intersection point, 4 spheres or satellites.
EGNOS is the European equivalent of
WAAS
Describe how differential correction and WAAS are similar and how they are different.
WAAS is similar to DGPS in that a correction is calculated and picked up by your receiver in addition to signals from the regular 4 satellites; however, in this case the correction is sent from an additional new satellite. not from and Earth-bound station.
Which datum does NAVSTAR GPS use for coordinate locations?
WGS84
the datum used by GPS is
WGS84
provide an example of spatial analysis
Within climate science, I'm interested in studying how precipitation varies over space which is an example of spatial analysis since it examines the spatial characteristics of data or how objects relate to one another across distances.
Geographic Information System (GIS)
a computer-based set of hardware and software used to capture, analyze, manipulate, and visualize geospatial information.
vector data model
a conceptualization of the world that represents spatial data as a series of vector objects (points, lines, and polygons)
small-scale maps
a map with a lower value for its representative fraction; such maps will usually show a large amount of geographic area
false easting
a measurement made east (or west) of an imaginary meridian set up for a particular zone. the value for easting in UTM is referred to as a false easting since the easting calculation is based on an imaginary central meridian in each zone.
Differential Correction (DGPS)
a method of using a group-based correction in addition to the satellite signals to determine position. one or more base stations are used at locations on the ground to provide a correction for GPS position determination.
buffer
a polygon of spatial proximity built around a feature
a datum represents
a reference surface used in computing coordinates
define how spatial query differs from an SQL attribute query
a spatial query selects records or objects from one layer based on their spatial relationship with other layers, rather than using attributes which is what SQL attribute query does.
attribute table
a spreadsheet-style form where the rows consist of individual objects and the columns are the attributes associated with those objects
suitability index
a system whereby locations are ranked according to how well they fit a set of criteria
a map projection is
a translation of locations on the earth's surface to their corresponding locations on a flat surface
union
a type of GIS overlay that combines all features from both layers
symmetrical difference
a type of GIS overlay that retains all features from both layers except for the features that they have in common
intersect
a type of GIS overlay that retains the features that are common to two layers
identity
a type of GIS overly that retains all features from the first layer along with the features it has in common with the second layer
ordinal data
a type of data that refers solely to a ranking of some kind - the value is just a ranking not a measure of what that ranking is based on
ratio data
a type of numerical data in which the difference between numbers is significant, but there is a fixed non-arbitrary zero point associated with the data.
interval data
a type of numerical data in which the difference between numbers is significant, but there is no fixed non-arbitrary zero point associated with the data.
nominal data
a typed of data that is a unique identifier of some kind - if numerical, the difference between numbers are not significant (i.e. social security number, telephone number, etc)
raster data model
a way of representing spatial data that utilizes a series of equally spaced and sized grid cells
ephemeris error can result in what level of error in GPS accuracy
about 2 meters
Remote sensing
acquisition of data and imagery from the use of satellites (satellite imagery) or aircraft (aerial photography)
The difference between a geoid and ellipsoid models of the earth's surface
an ellipsoid is a model of the earth as a rounded ellipse-shape sphere. a geiod uses the mean sea level as the base to account for the fact that Earth doesn't have a smoothed surface because gravitational forces affect different part of Earth in different ways causing some areas to be out of sync with the ellipsoid.
multipath errors
an error caused by a delay in the signal due to reflecting from surfaces before reaching the receiver.
map algebra
combing data sets together using simple mathematical operators
metadata
descriptive information about geospatial data
which of the following receivers can pick up the military p-code
dual frequency
when the correct satellite position is not being sent, what type of error is being encountered?
ephemeris
spatial analysis
examining the characteristics or features of spatial data, or how features spatially relate to one another
trilateration
finding a location in relation to three points of reference.
the shortest distance between two points on a sphere is the
great circle distance
visual hierarchy
how features are displayed on a map to emphasize their level of prominence
topology in GIS refers to
how objects are connected to one another independently of their coordinates
what makes geospatial data unique
it is connected to a real world location
Geospatial data
items that are tied to specific real world locations; location based data
UTM coordinates are measured in
meters
when the GPS signals bounce off objects to arrive later than anticipated, what error is occurring?
multipath
a persons social security number would represent what type of numerical data?
nominal
boolean operator
one of the four connectors (AND, OR, NOT, XOR) used in building compound queries
relational operator
one of the six connectors (=, <>, <, >, >=, or <=) used to build a query
Example of how geospatial technology is used in both the private and public sectors.
private: realtor and appraisers create and examine maps of neighborhoods, and they use high resolution areial photography to look at and assess properties public: law enforcement officials plot crime locations using GIS to analyze patters and determine potential new crime areas
the distance between a receiver and one satellite is referred to as
pseudorange
in an attribute table, each object is stored as a
record
list the different types of relational and boolean operators used in SQL
relational: equal, not equal, greater than, less than, greater than or equal, less than or equal boolean: and, or, not, xor
Define spatial thinking and concepts of space.
spatial thinking is thinking that finds meaning in the shape, size, orientation, location, direction or trajectory of objects, processes or phenomena
SQL
structured query language - a formal setup for building queries (the conditions used to retrieve data from a database)
NAVSTAR GPS
the US global positioning system, where the term GPS originated from as this was the initial development of the set up by the US Department of Defense. this is on type of geospatial technology (GNSS) that allows the user to locate their position on the earth's surface.
dissolve
the ability of GIS to combine polygons with the same features together
cartography
the art and science of creating and designing maps
overlay operation
the combining of two or more layers in the GIS