EAS 531 Midterm
Raster extent
# of cols, # of rows
In row and column space, the upper left cell is usually
1,1
ArcGIS representation of projections
Geographic, aka GCS
Observed element (2types)
Object model, field model
3 common ellipsoid shapes
Clarke 1866, GRS 1980, WGS 1984
3 uses of multispectral satellite images
Classification of land cover or other features, biophysical parameters (continuous data), others (real time monitoring ,weather)
Fields
Earth is a continuous surface characterized by a number of properties (elevaiton, pH)
Longitutde is measuring _____ relative to _____
East West relative to the Greenwich Meridian
location in raster
coordinates assigned to the entire grid and also to each cell
what dataset has arc attribute tables?
coverages
digitizing polygons with autcomplete
create a new polygon by snapping to an existing one
Plate Carree Projection
cylindrical projection that distorts areas and shapes
3 families of projections
cylindrical, conic, azimuthal
3 uses of GPS
field digitizing, navigation, tracking
computer map window projection defined by ____-
first data source added, subsequent data will be reprojected on the fly
Object model
focus is on the object (objects can have different attributes)
Field model
focus on the attribute (varies over space)
in the US state plane system, projected origins and coordinate origins are established -__
for each zone
data structure
formal symbolic representation of specific things in the data model (coordinates, attribute data) Organized set of files for managing entities/fields defined in the data model
domains are defined at hte level of hte
geodatabase
spatial sample
geographic measurements based on a sample of space
All layers are precisely ____
geolocated
connectivity and adjacency
geometric relationships between features in a single GIS layer (no overshoots or undershoots)
Raster cells have X, Y locations that are
georeferenced
remote sensing
getting info about an object/area through analysis of data acquired by a device that is not in contact with the object
GADM
global administrative boundaries available by country
GNSS
global navigation satellite systems
SEDAC
global or national, social, environmental, and health themed data
Open street map
global road data
ASTER GDEM
global, from aster sensor, elevation data
symbolization for ordinal
gradations in color or symbol size
2 ways to select by location
graphical interaction pointer (clicking on what you want) topological relationships to features in the same or a different data set
Projections
mathematically defined conversions from location on 3D earth to 2D space
spatial census
measure or count every object or location in an area
RMSE
measures the fit of transformation
why does GIS need simplification or sampling framework
measuring everything everywehre all the time is impossible!
Balance
minimize blank space, efficient use of space
why use relational database?
more efficient, makes updating easier, can mix and match data from various tables
best if you have ____ georeferenced points
more than 15
feature dataset
multiple feature classes with the same projection/datum can be combined into this
Each spatial feature in a vector data set can have _____
multiple values
geodatabase contains _____
multiple vector feature datasets and/or vector feature classes. can also contain raster
NLCD
national land cover database, created from landsat
USGS
national map of the US
natural color and fake color
natural - assigning RGB . to their true values fake - assigning other values to RGB
3 resampling methods for raster
nearest neighbor, bilinear interpolation, cubic convolution
vector is prefered for ____ analysis
network
is there a single set of topology rules or relationships across software packages or data formats?
no
dangling nodes
node connection to only one arc (overshoot or undershoot)
Shapefiles are ______ and use a _____ objected approach
non topological, use disconnected object approach
NAD83 best fit for, based on
north america, GRS80
NAD 27 best fit for, based on
north america, clarke 1866
1st order transformation
not warped. rescaled, rotated, etc
number of bands
number of layers
difference between feature and object
object does not have a known location, feature is an object with a location
line in vector is an ______
ordered set of points
database
organized collection of tables, files, data. formall defined and centrally controlled colleciton of data
spatial cognition
our understanding of hte geographic world
How to make a distance raster?
perform GIS functions on vector data to output a raster
spatial resolution and extent
pixel size and image extent
ESRI GIS coverage enforces
planar topology
Thematic map example
population change map by district
5 uses for GIS
Platform for collecting data Database and data repos Tool for analysis Visualization Land, resources, and infrastructure management tool
Coordinate origins in the UTM
X = 500,000 west of central meridian (false easting) Y = one for northern hemi (equator), different one for southern hemisphere
in cartesian coordinate space, the lower left cell is
X min Y min
Layers have their own internal ____
abstraction and logic
Lidar sensing
active, aircraft mounted, cannot see through clouds, records geo location and height
radar sensors
active, light and clouds irrelevant, most are space borne, use radio
datum location information corresponds to
actual surveyed coordinates at Earth Locations
Non-map representations of the earth
air photos and satellite images, photos and drawings
snapping
allows you to create features that automatically connect to others
attributes can be measured using
almost any measurement device
TIGER
census geography. Census tracts, block groups, blocks geogrpahic data. can be joined to census data
line of contact in UTM
central meridian
flat bed scanner
cheap, limited in size
Thematic raster maps are created from
classification of remotely sensed images
polygon is a single _____ or a set of ____
closed line, connected lines forming an enclosed area
______ are commonly used for continuous raster data with ratio attributes
color ramps
legibility
common font throughout, less is more
symbolization for nominal
common symbol for all features or a unique color or symbol for features with a different value
Mercator Projection is ______, has correct ______, exaggerates _____, designed for______
conformal, correct shapes, exaggerates high latitutde area, navigation
with coverage, features are __
connected
Attribute domains
constrains values to values you specify Coded value or range
records in an attribute table
contain a set of values for a single entity
Raster is prefered for ___ data analysis
continuous
can't do attribute table for _____ data, only for _____
continuous, integer
CORS
continuously operating reference stations - allows for differential correction post processing
issues of trilateration
position dilution of precision (PDOP) based on geometric arrangements of satellites when satellites are closer together, there is a large area of uncertainty
vector spatial precision is limited by____
positional measurements
Objects
present a view of hte world in which the earth's surface is populated by a number of discrete entities
JPEG is only good for
presentation, not looking at data
measurement
process of extracting data about the world
normalization
process of identifying redundancies and storing them in separate tables
another word for cartesian coordinates
projected coordinates
prj
projection information
US state plane coordinate system
projects the 3D earth into separate projections for each state, some have more than one zone
How does GPS work?
pseudo random code (radio signal) generated by satellite and decoded by receiver. Receiver compares signals and determines the time it took to travel from satellite to receiver
ratio attribute
quantitative values, equality of units, non-arbitrary 0 measurement, ratios between values makes sense
Interval attribute
quantitative, equality of units, arbitrary 0 measure
domain
range of values that features may take
ESRI GRID is a _____ format
raster
raster is good for _____ output, vector is good for _____ output
raster - images vector - maps
difference in reclassification between raster and vector
raster - just recode vector - recode, then dissolve
raster is ____ in coordinate conversion, vector is _____ in coordinate conversion
raster - slow vector - simple
Path of less abstract to more abstract
real world --> data model --> data structure --> machine code
in the attributre table, the rows are the ____ and the columns are the _____
records, fields
hierachry
relative importance should be clear, use placement
georeferencing a raster image file
resample the image pixel values to fit the new raster geometry
graphic scale uses
scale bar
MMU dependent on
scale over original source and goals of cartographers
topology
science and math of spatial relationships
Real-float numbers use ___
scientific notation
5 ways to increase GPS precision
select satellites that are not low to the horizon select low PDOP threshold take multiple readings at a point and average them apply differential correction use more expensive carrier phase receivers
set-based approach for retrieving data
select subset of records based on a logical expression
Map content is ____
selective, maker has control
relational databases store ______ connected by _____
separate types of entities in separate tables, connected by a key variable
shp
shape format, feature geometry itself
shx
shape index format, positional index of the feature geometry
Every projection distorts ____
shape, area, or direction
SRTM GDEM
shuttle radar topography mission, NASA, global. Elevation data
Atmospheric interference with signal sent from GPS
signal is delayed, solution: mask out low angle satellites
keep roughly ______ for hues of all categories of nominal
similar saturation and value
simple vs compound data query
simple - one conditional statement compound - use Boolean logic
raster are ____ and _____ than vector as data models
simple and larger
domains advantage
simplify entering data, validate entered data
Vector point is made of a _____
single coordinate pair
sliver polygon
small spurious polygon between two others as a result of overlap
Reference map communicates
spatial assc between various phenomena
Vector data uses ___
spatial features - points, lines, and polygons
Location in vector
spatial features with coordinates assigned to points
feature classes inside a feature dataset inherit ____ from dataset
spatial reference
spatial operation data can be ___, ____, ____
spatial, non spatial, used for another operation
database management system
specialized computer program for organiziang and managing data
hue
spectral color
Geographic framework for michigan
standardizes basic info for the state features include roads, lakes, streams, school districts. uses Michigan GeoRef
NAVSTAR GPS
started in 1995, continually improving
node
starting and ending points of the line
Data from FAO of the UN
stat data, broad range land, forest, agri, food, pop
in ArcGIS, coordinates are stored _____ and define _____
stored in the permanent spatial portion of GIS, define projection of hte data
arc attribute table
stores relationships between points, lines/arcs, and polygons. preserves topology
DBMS main function
storing and retrieving data as requested by software
GCS is useful for
storing large, global dataset files, project as needed
Pyramids
subsample data to be displayed more rapidly
WGS 84 is the best fit for ____, origin is
the globe, origin is the Earth's center of mass
Real world abstraction
the real world physical entities or continuous fields
Geoid
the shape that the surface of the oceans would take under the influence of Earth's gravitation and rotation alone, in the absence of other influences such as winds and tides.
resolution
the smallest resolvable unit
use two colors in a blended hue ramp if
the variable range has a center
four ways to represent ratio attributes in raster
total value over the cell, average value, extreme value, cell center
Universal Transverse Mercator (UTM)
transverse mercator projection for each of 60 different zones, each 6 degrees of longitude wide
in shapefile, boundaries are recorded _____
twice
what to do if your datum/projection is defined in your GIS layer but you want to convert it?
use a projection - reprojecting, converting between projections and datum use PROJECT in ArcMap Geographic transformation - changes the datum
symbolization for ratio
use gradations in colors or symbol size, color ramps, proportional symbols
what to do if your layer is neither defined nor projected
use ground control point method and a statistical transformation (georectification) to match the geometry of a digital reference map or images taht has a known datum/projection using least squares regression
How do geodatabases store vector data?
uses feature class and feature datasets to store vector data
generalization
values from a census are generalized over geographic units
Ordinal attribute
values that have a natural order or rank
attributes are considered____ and are often stored in _____
variables, stored in a data table called an attribute table
2nd order transformaiton
warping, most often used
your choice of scale affects
what can be measured and how it's represnted
Abstraction in map making
what is important for the map? extent vs purpuse
WAAS
wide area augmentation system - allows for correction on the fly
In Raster, each grid cell is coded ____
with a single value
geodatabases have topology ______
within and between feature classes
raster spatial precision is set by ____
cell size
spatial operation
manipulates or calculates based on coordinates or attribute values
WWF ecoregions
825 terrestrial ecoregions in 14 biomes
if one bit is used to indicate sign, what is the range of values?
-128 to 127
3 benefits of Geodatabase
1. allows for data models to be formalized before creation. predefine all feature classes etc 2. is topological within and between classes 3. topology can be defined by rules and stored as a component of a feature dataset
3 things GIS uses topology for
1. enforce the geometry of vector features in a single GIS layer 2. define geometric relationships between vector features in a single GIS layer 3. enforce spatial relationships between GIS layers
topology rules can do two things
1. monitor spatial relationships of features in a single feature class. 2. restrict the relationships that exist between feature classes
2 solutions for if you need a single coordinate system for an area that spans multiple UTM or state plan zones?
1. project all to one 2. create a new single custom projection for the entire area
3 things GIS requires
1. system for precise measurement of location 2. attribute scheme and acceptance of attribute defs 3. spatial, thematic, and temporal simplification or sampling framework
CCI global land cover
12 classes of data
Cartesian/projected : location referenced relative to _____
2 perpendicular axes (x,y)
8 bit max storage
256 values (0-255)
How many zones does Michigan hvae in the US state plane coordinate system?
3 - north, central, south
single precision floating can be represented wit
32 bit
how many satellite signals do you need to locate yourself?
4
when you ½ the cell size the file size is ____
4x as large. 4 times as many cells
CEP
50% of the GPS fixes fall within this area circle's radius around the true mean
double precision floating can be represented with
64 bits
16 bit max storage
65,536 values
1 byte =
8 bits
coordinate systems in ArcMap have 5 things
A projeciton an ellipsoid/datum projection lines of contact (central meridian or standard parallels) units coordinate system origins
characters are coded with
ASCII coding
Equal area conic (1 type, what does it preserve)
Alber's Equal Area preserves area at the expense of shapes
4 advantages of DBMS in large enterprise
Control simultaneous multi-user access Data independence (structured independently of the apps) Multiple applications centralized control and maintenance
2 units for angles and the conversion between them
Decimal degrees and degrees-minutes-seconds 1 degree = 60 minutes
3 non-lossy
ESRI GRID, ERDAS/IMAGINE, TIF
units of distance measure in projected data
English : inches, feet Metric
multipath errors
GPS is line of sight technology signal bounces of nearby objects can screen via signal to noise ratio
GIS acronym
Geographic Information System
fine spatial resolution (3 examples, time)
Ikonos, quickbird, WorldView. infrequent coverage, pointable
Lossy format
JPEG
coarse spatial resolution (2 examples, frequency)
MODIS, AVHRR daily data
Do pyramids alter your data?
No!
is your data projected in GCS
No! Simply based on datum/ellipsoid, uses angular units
3 attribute types in GIS and how they're stored
Nominal -text field or integer Ordinal - text field or integer Ratio - integer or real number
Latitude is measuring _____ relative to _____
North South relative to the Equator
SQL query format
Select ____ from -____ where _____ and/or/not _____
3 steps in building map model
Spatial cognition measurement symbolization
GPS
US satellite segment
How does differential correction work?
a base station at a precisely known location records its own GPS location. Different between the recorded and true value = error in GPS estimated location. can adjust post data collection or real time
each feature class in a geo db is available as ____-
a layer for display, like a shapefile
Radial coordinates: location referenced relative to _____
a single axis (x)
Each vector data layer in GIS contains ___
a single feature class
geographical coordinates : reference is made using ____
angle positioned at the center of th earth
Radial coordinates : measurement is ____
angular displacement from x and linear distance (r) from origin (0,0)
____ within a feature class inside a geodatabase can use a domain inside that geodatabase
any attribute
Object model empty space
any space between the entities
if you want your projection to preserve: area, shape, direction
area - equal area shape - conformal direction - conformal or azimuthal
Equal area cylindrical
areas are correct, shapes distorted
UTM is best for
areas with longer NS extents and not EW extents
dbf
attribute format, columnar attributes for each shape
Fields are defined by
attribute name, type (text, integer, float, etc)
fields in attribute table hold
attributes or variables describing all entities
point samples dependent on
average sample spacing
Pro and con of equal interval
bad for highly skewed data, easier to interpret
natural breaks
balance between equal and quantiles
figure ground
be clear what is the information highlighted and what is the background, contrast and color
2 ways to select features in ArcGIS
by attribute, by locaiton
attribute range in raster is determined by
bytes
3 options for when 2 vector polygons span one raster cell
can do largest share rule or central point rule, presence or absence
Resolution in raster
cell size
In GIS, information is organized into data ____ that represent ____
data layers, single theme
simplest form of spatial operation
data query
Compression is basically
data storage
resolution of polygons
defined by "minimum mapping unit"
Michigan GEOREF
defined to allow referencing locations throughout the state of michigan on a single projection and coordinate system
prj file
defines projections
Attributes
describe characteristics of either locations/cells or geographic features
Can use infrared to ___
differentiate between surfaces ,differnet sufraces have different spectral reflectance curves
heads up digitizing
digitizing on screen with a georeferenced map or image displayed and use a mouse to record locations
non-lossy compression is good for
discrete data with large homogenous areas
Cartesian measurements are in _____
distance along each axis from the origin (0,0)
Thematic map communicates
distribution of a single property or relationship among several
quantiles
divides range into n categories with the same number of features
Equal interval
divides the range into categories that all have the same value range
Empty space in field model
does not exist
Most zones in the US state plane coordinate system use
either a ™ projection (cylindrical) or a lambert projection
DEM
elevation data
datums
ellipsoids with location information (lat and long)
planarity
enforcing geometry requires that all features occur on a 2d surface. No overlapping
manual digitizing tablet
enter points through map document placed on digitizer and use mouse to record locations
data model
entities or fields represented in a spatial database and hte relationships among them (raster, vector, object based)
symbolization
established rules for relating marks to real world entities or continuous fields
Satellites know their (3)
exact altitude, position in orbit, and position wrt the WGS84 ellipsoid
drum scanner
expensive, accurate, can handle large documents
tissot indicatrix
graphically displays distortion. Helps you see what type of distortion occurs in the size, shape, and orientation of ellipses that would be circles were they located on the spherical Earth's surface
Raster data uses ____
grid cells
feature class
group of features of the same type (analogous to vector layer in the geo db)
pro and con of quintiles
highlights differences in the values of features, hard to read
spectral resolution
how many bands (Wavelengths) can the sensor collect simultaneously
temporal resolution
how often does a location get sampled?
saturation
how rich or vivid a color is, deep/saturated
Nominal attribute
identifier value, names, letters, numbers (phones, SSN)
why use pyramids?
improves the performance of rasters
if your data is not projected, it will display ...
in a plate carree projection with coordinates in Lat/long
Selective availability
in the 1990s, intentional degradation of public GPS. reduces precision
high accuracy in UTM occurs
in zones less than a few degrees in east west extent
Maps are a form of _____, because they can be interpreted
information storage
value
intensity (lightness or darkness)
vertices
intermediate points on the line
join vs relate
join - appends the attributes to the table based on a common field relate - defines a relationship between the two tables based on a common field, does not append
conformal conic (1 type, preserves)
lambert conformal - preserves shapes at the expense of areas
MODIS
land cover map from NASA, 17 land cover classes
moderate spatial resolution (1 example, time)
landsat, 16 days
1:5000 is a ____ scale map than 1:500,000
larger
large scale map covers ____ area, has ___detail , and ____ denominator
less area, more detail, smaller denom
Connectivity applies to ____ and adjacency applies to _____
lines, polygons
______ and ______ between marks on maps and what the refer to
logical and scientific correspondence
selecting by attribute
logical expression to interact with attribute table
Non-lossy format
maintains original cell values