Midterm Exam Flashcards
(130 cards)
0
Q
Spatial
A
Refers to data models that are related to or existing within space
1
Q
Definition of GIS
A
An organized collection of computer hardware, software geographic data and personnel designed to efficiently capture, store, manipulate, analyze, and display all forms of geographically referenced information
2
Q
Geospatial
A
Data that can be associated with geographic locations-locations in the space around us- that can normally be shown as features on a map
3
Q
CADD
A
Computer aided design/drafting.
Technology for symbolically representing features, in Cartesian coordinate system
Used for the design and display of graphical data. Must commonly used for engineering, planning, and illustrating.
GIS is not the same as CADD because GIS can store information about spatial features separately from the spatial component of those features, and analyze that spatial data.
CAD/CAM are non-geographic
4
Q
MIS
A
Management information system.
management systems are non-spatial, so GIS is not simply MIS
5
Q
ArcGIS
A
ESRI’s geographic information system
6
Q
Spatial analysis
A
The formal techniques which study entities using their topological, geometric, or geographic properties
ESRI:The process of examining the locations, attributes, and relationships of features in spatial data through overlay and other analytical techniques in order to address a question or gain useful knowledge.
Spatial analysis extracts or creates new information from spatial data.
7
Q
ESRI
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A supplier of GIS software. Maker of ArcGIS
8
Q
ArcGIS licensing levels
A
Basic
standard- adds tools for editing geodatabases
advanced- all the capabilities of ArcEditor plus additional geoprocessing tools
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Q
Geodatabase
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The common data storage and management framework for GIS
A container for spatial and attribute data
Contains feature classes, and grouped feature classes in a feature dataset
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Q
GIS queries
A
Location- what is at...? Condition- where is it....? Trend- what has changed....? Routing- what is the best way...? Pattern- what is the pattern...? Modeling- what if....?
11
Q
Hierarchy of spatial data structure
A
Spatial concept- perception of space ex. 2d
Spatial data models- formalize the spatial concept. Ex vector or raster
Low level spatial data structures- implementations of the concept… Data storage and performance efficiency. Ex. Shape file, geodatabase
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Q
Model
A
Simplified view of the real world.
Models used in GIS to represent geographic space
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Q
Coordinate data
A
Gives an object’s location
Quantify or define location of the object
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Q
Attribute data
A
Gives an object’s characteristics
Describe the characteristics of the object
Records non-spatial information about the entity
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Q
Nominal
A
Descriptive characteristics, can’t be measured
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Q
Ordinal
A
Imply a ranked order, but no scale
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Q
Interval/ratio
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Use numerical values to imply a magnitude
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Q
Discrete data
A
Represents phenomena with distinct boundaries. Usually represented by vector data
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Q
Continuous data
A
Data that varies without discrete steps. Ex. Temperature. Usually represented by raster data
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Q
Node
A
Special type of vertex that begins/ends a polyline
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Q
Vertex
A
Points on a poly line
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Q
Point
A
Vector geometry. Single point to represent an object
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Q
Polyline
A
Vector geometry. Comprised of vertices connected by arcs
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Polygon
Vector geometry. Represent are features that begin and end with the same vertex
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Topology
Represents a set of rules that ensure connectivity, contiguity, and adjacency between features in a data set.
A numerical description of the relationships between geographic features. Mathematical procedure for explicitly defining spatial relationships
Geometric properties that are shared by multiple objects.
Can be used to perform integrity checks on the data
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Planar topology
Prevents overlap of features in the same layer
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Adjacency
Ensures correct alignment for polygons
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Connectivity
Ensures line files are connected
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Contiguity
Every arc has a direction
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Containment
An enclosed polygon has a measurable area
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Raster cells
Pixels. Set of regularly spaced cells to represent the world. Typically square with coordinates corresponding to the center.
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Resolution
Cell size. Dictates the quality of the model... Small cell size means greater accuracy
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DBMS
Database management system. System for storage, access, and manipulation of GIS data. Contains data objects, attributes, spatial reference, and topology rules.
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Relational database
A data structure in which collections of tables are logically associated with each other by shared fields
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Geoid
A gravitational surface of equal potential, which approximates mean sea level
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Ellipsoid
A simplified mathematical surface used to represent the earth
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Flattening factor
Flattening due to the earth's rotation. (a-b)/a
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Vertical datums
Using for measuring elevations
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UTM
Universal transverse Mercator , a global coordinate system system
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Datum
A frame of reference which measurements are made relative to.
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DRG
Digital raster graphics. Raster image of a scanned USGS topographic map
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SDI
Spatial data infrastructure. A frame work of spatial data, metadata, users, and tools that are interactively connected in order to use spatial data in an efficient and flexible way.
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NSDI
US national spatial data infrastructure
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Circular A16
Document that enacted the US NSDI. Requires that metadata be written for all spatial data derived using government funds.
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Metadata
Data about data. Describes content, quality, condition, and characteristics of the data.
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FGDC
Federal geographic data committee
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The 7 framework layers
```
Digital ortho imagery
Elevation
Hydro geography
Transportation
Boundaries
Cadastral
Geodetic control
```
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The national map
Contains ortho rectified imagery, land cover , elevation, vector layers, geographic names
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DOQQ
Digital ortho quarter quads. A digital orthophoto quadrangle divided into four parts
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NED
National elevation data set
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NLCD
National land cover data set
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NWI
National wetlands inventory
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NHD
National hydrography data set
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GUBs
Government unit boundaries
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ESRI shapefile
A vector data storage format for storing the location, shape, and attributes of geographic features. Stored in a set of related files and contains one feature class
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ESRI coverage
A data model for storing geographic features. Stores a set of thematically associated data considered to be a unit. Features stored as both primary features (points, lines, polygons) and secondary features (tics, links, annotation)
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GNSS
global navigational satellite systems
a satellite-based technology that provides horizontal and vertical positional information/data- estimates of the receiver's location
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GPS
NAVSTAR global positioning system. created by US DOD
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GNSS components
1. satellite segment (constellation)-orbitting
2. control segment- earth-based stations, observe, maintain, and manage the satellite system
3. user segment - receivers
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GPS satellite segment characteristics
21 satellites, orbit at 20,000 km, each satellite orbits the planet twice a day, typically 4-8 satellites visible from any point at any time
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GPS control segment characteristics
master control station is in cheyenne mountain, colorado
maintains and manages the GPS satellite system: satellite health records and transmits corrections, tracking info from each station, timing data from the US naval observatory, earth data from US DMA
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GPS receiver segment characteristics
- interface: most have a graphics screen, page by page options
- can specify coordinates system and units for collection
- marking a point: accuracy, averaging
- setting up a track
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broadcast signals for GPS
based on radio signals broadcast from GPS satellites
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how does a GPS determine position?
time between signal transmission from satellite and reception by receiver can be used to estimate range distance
determined by the simultaneous measurement of range distance from four satellites
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errors and accuracy considerations for GPS
- atmospheric and ionospheric delays: our atmosphere is not a vacuum
- satellite system operation
- receiver errors: multi path signals- signals bounce off walls, buildings, etc
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how can GPS accuracy be improved?
- having more than 4 satellites will improve accuracy
- accuracy can be improved by averaging the range distance for a period of time... requires the receiver to remain stationary
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area of uncertainty
the product of range error
| the wider the spread of satellites, the smaller the area of uncertainty
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PDOP
positional Dilution of Precison
the ratio of the volume of an ideal tetrahedron to the volume of the tetrahedron formed by four ideally widespread satellites.
ideally spaced satellites would be four at 120 degrees
ideal PDOP=1 (lower values better)
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differential correction
correction of field data using errors from a nearby base-station receiver
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steps for differential correction
1. field receiver gets estimate of its x,y location
2. base station nearby has a previously established, highly accurate known location
3. base station collects estimates of its known location for all times and all possible sets of satellites
4. base station calculates x and y deltas for the estimates
5. using this delta set, corrections are made to the estimate made by the field receiver
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remote sensing
the study of something without making physical contact with the object of study
the acquisition and measurement of data/information on some property of a phenomenon, object, or material by a recording device not in physical, intimate contact with the feature under surveillance
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satellite imagery
consists of images of Earth or other planets collected by artificial satellites.
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aerial photography (and orthoimagery)
s an aerial photograph geometrically corrected ("orthorectified") such that the scale is uniform: the photo has the same lack of distortion as a map. Unlike an uncorrected aerial photograph, an orthophotograph can be used to measure true distances, because it is an accurate representation of the Earth's surface, having been adjusted for topographic relief,[1] lens distortion, and camera tilt.
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LiDAR
Light Detection and Ranging (elevation models!)
| elevation rasters and/or vector contours from surface modeling using LiDAR data
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electromagnetic spectrum
the range of all possible frequencies of electromagnetic radiation
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spatial resolution
ability to distinguish small details of an object
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spectral resolution
measure of its ability to resolve features in the electromagnetic spectrum.
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sensor (active and passive)
passive- typically energy reflected from the sun
| active- energy from system source (radar, LiDAR, etc)
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platform
the platform supports the sensor...
ground-based
satellite
aerial
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panchromatic
cover a wide band of wavelengths in or near the visible light spectrum...high spatial resolution
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multispectral
cover two or more spectral bands simultaneously
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hyperspectral
cover hundreds of very narrow spectral bands (high spectral resolution)
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spectral signature
derived from hyperspectral data.
the specific combination of emitted, reflected or absorbed electromagnetic radiation (EM) at varying wavelengths which can uniquely identify an object
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LandSat program
developed in the 70's by NASA, NOAA, AND USGS
landsat 1-7.. 7 is the primary source of current data
30m multispectral resolution 7 channels, 15m panchromatic
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classification system for remotely sensed data
system that classifies land cover classes, land-use classes, vegetation
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why do remote sensing?
allows study of objects that are too large for fieldwork (regions) over long periods (decades) and are possibly hazardous in nature
- agriculture
- geological/mining-fault detection, surficial mapping
- land resource management-forestry
- land sue monitoring
- environmental monitoring
- military
- emergency management
- mass market apps- ex google maps
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remote sensing system components
- target
- energy source
- transmission path
- sensor
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wavelength range of visible spectrum
400-700 nm
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relative wavelengths of electromagnetic spectrum (short to long)
```
gamma
x rays
ultraviolet
visible
infa red
microwaves
radio
long waves
```
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elements of space based remote sensing
1. energy source illumination (passive or active- sun or satellite)
2. radiation
3. interaction
4. sensor recording
5. transmission
6. reception and processing
7. interpretation and analysis and application
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spectral resolution vs spatial resolution
there is a resolution tradeoff .... spectral spatial
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types of RS sensors scanner types
whiskbroom, pushbroom
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supervised RS
analyst specifies certain "known" areas in the image, and statistics about the DNs in these areas are used to categorize the entire scene
this is referred to as the training stage
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unsupervised RS
no training stage, pixels are run through an iterative clustering algorithm, and "similar" groups of pixels are classified thematically
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true or false:
| in the value attribute table of and arcgis raster data set, each record corresponds to a unique pixel in the raster
False
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what makes up a GIS "feature"?
feature attribute/value + spatial geometry
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what is the domain of an attribute?
Attribute domains define what values are allowed in a field in a feature class or nonspatial attribute table.
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3 advantages of using a vector data model vs raster data model
advantages of vector:
- more compact storage
- smoother appearance of linear features
- facilitate the use of topological information
- most precise
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advantages of establishing topological relationships among vector features
- stores data more efficiently
- allows processing of larger data sets
- allows you to perform spatial analyses (ex. overlays)
- allows faster processing
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automatic routing operations are dependent on which type of topological feature?
contiguity
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what is a datum and why are there multiple datums for the same portion of the earth's surface?
datums are updated timely when more precise measurements become available
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projection sources
- at the center of the ellipsoid
- anitpodal
- at infinity
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4 types of distortion
- distances
- directions
- shapes
- areal sizes
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why is there always some sort of distortion?
it is impossible to preserve distances, directions, shapes, and aerial sizes all at the same time.
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what map type uses different coloration/shading of polygons based on values of an attribute in the attribute table?
choropleth
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what is the first step in developing a GIS database?
1. identify the information products that will be produced with your GIS.
107
which two types of data sources already exist (are secondary data sources)?
digital form data
| hardcopy maps
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how is metadata used to enable or facilitate data discovery, evaluation, and access?
tells you the properties and characteristics of the data.
| allows interoperability
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2 components of data models that are essential to GIS
coordinate data- object's location
| attribute data- object's characteristics
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origin
where all values are zero
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types of attributes
nominal, ordinal, interval/ratio
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structure of an attribute table
rows/records: each represents an individual object
| columns/fields: each represents an attribute, ex. population
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types of geometric properties (topology)
adjacency
connectivity
containment
contiguity
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why topology matters
- detect and prevent digitizing errors
- overlay analysis
- ensure the spatial integrity of your data
- efficiency in storage
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in order to establish topologic rules between 2 or more feature classes...
they must be in the same feature dataset
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components, advantages DBMS
contains data objects, attributes, spatial reference, and topology rules. advantages: allows for centralized data storage and management, efficiency.
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geodatabase object types
feature classes, feature datasets
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geodatabase object types
attribute data, geographic features, surface modeling, gps coordinates, survey measurements
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set algebra operators
,=,<>
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boolean operators
and, or, not
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Two primary types coordinate (reference) systems for describing locations on the earth’s surface:
spherical (lattitude and longitude) and Cartesian coordinate
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components of a datum
1. ellipsoid specification, with an origin
| 2. observations: the precise coordinates of permanently mounted plates called benchmarks
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WMS-detail
Web Map Service
| delivers pictures of features from geographic datasets
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service
collection of operations, accessible through and interface, that allows a user to evoke a behavior of value to the user
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web service
the specification, offering, discovery, request, and performance of work relies on an Internet protocol background
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map request
with parameters provided, returns a map image
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interoperability
the capability to communicate execute programs, or transfer data among various functional units in a manner that requires the user to have little or no knowledge of the unique characteristics of those units
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how does WMS differ from WFS?
WFS= web feature service, delivers coordinate pair and attribute values for the features of the geographic data set
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capabilities request
returns parameters about the WMS and the available layers
