GIS Flashcards Exam 1

Geography
GIS
A computer system for capturing, storing, querying, analyzing, and displaying geospatial data
geospatial data
data that describe both the locations and characteristics of spatial features on the Earth’s surface
vector data model
a spatial data model that uses points and their x-y- coordinates to construct spatial features of points, lines, and polygons
georelational data model
a vector data model that uses a split system to store geometries and attributes
data exploration
data centered query and analysis
projection
process of transforming the spatial relationship of features on the Earth’s surface to a flat map
reprojection
projection of spatial data from one spatial coordinate system to another
geographic coordinate system
a location reference system for spatial features on the earth’s surface
latitude
– the angle north or south of the equatorial plane
longitude
the angle east or west of the prime meridian
meridians
line of longitude (East and West)
parallels
line of latitude (N and S)
sphere
perfectly round geometric object in 3D space
spheroid/ellipsoid
a model that approximates the earth
geoid
closer approximation of earth than a spheroid
Clarke 1866
a ground measured spheroid which is the basis for NAD27.
NAD 27
North american datum of 1927… based on clarke 1886. centered in Meades Ranch, Kansas.
NAD 83
North american datum of 1983… based on the GRS80 spheroid… origin at center of spheroid
GRS 80
a satellite determined spheroid developed in 1980- Geodetic Reference System 1980
WGS 84
satellite determined spheroid for the world geodetic system 1984
datum
the basis for calculating the geographic coordinates of a a location. A spheroid is a required input to the derivation of a datum.
map projection
a systematic arrangement of parallels and meridians on a plane surface
false easting/northing
a value applied to the origin of a coordinate system to change the x or y-coordinate readings.
state plane coordinate system
a coordinate system developed in the 1930s to permanently record original land survey monument locations in the US. Most states have more than one zone based on SPC27 or SPC83
map scale
ratio of the distance on the map to the actual distance on the ground.
projected coordinate system
a plane coordinate system based on a map projection
on-the-fly projection
displaying datasets based on different coordinate systems… a means of using projection files available and converting datasets to common coordinate systems.
Coverage (arcinfo)
the vector data model associated with the ARCInfo software package. Example of georelational data model, which uses a split system to store geometries and attributes.
shapefile (ArcView)
the vector data model associated with the ArcView software package. Example of georelational data model, which uses a split system to store geometries and attributes.
geodatabase (ArcGIS)
the vector data model associated with the ArcGIS software package… an example of object-based data model, which stores geometries and attributes in a single system… AN object-based vector data model developed by Esri
Esri
environmental systems research institute, developer of ARCGis
Point
has zero dimension and has only the property of location… example, well, tree, gravel pit… a spatial feature represented by a pair of coordinates and has only the geometric property of location
Line
A spatial feature that has one dimension and has the property of length in addition to location. Has two end points and points in between to mark the shape of the line. Represented by a series of points
Polygon
two dimensional shape which has the properties of area and perimeter in addition to location. Made of connected, closed, non intersecting line segments. A spatial feature that is represented by a series of lines and has the geometric properties of location, size, and perimeter
Topology
A subfield of mathematics that studies the properties of geometric objects that remain invariant under certain transformations such as bending and stretching
TIGER
an early application of topology in geospatial technology – the Topologically Integrated Geographic Encoding and Referencing database created by the US Census Bureau.
DLG
another well known example of vector data with built-in topology. Digital representations of point, line, and area features from USGS quadrangle maps.
georelational data model (coverage & shapefile)
type of model which stores geometries and attributes in a split system – geometries in graphic files and attributes in relational database. GIS data model that stores geometries and attributes n two separated by related file systems
object-based data model (geodatabase)
type of model which treats geospatial models as objects which can represent spatial features such as a road, or a hydrological unit… a vector data model that uses objects to organize spatial data.
feature class
a data set that stores features of the same geometry type in a geodatabase… stores spatial features of the same geometry type
feature dataset
a collection of feature classes in a geodatabase that share the same coordinate system and area extent…stores feature classes that share the same coordinate system and area extent (BOTH FEATURE CLASSES AND FEATURE DATASETS ARE COMPONENTS OF GEODATABASES)
NHDinGEO
the acronym used by the National Hydrography Dataset program to designate their data in geodatabases
raster data model
a data model that uses rows, columns, and cells to construct spatial features
cell value
each cell in a raster contains a value which represents a characteristic of a spatial phenomenon at the location denoted by its row and column
integer (categorical)
– a raster that contains cell values of integers
floating-point (continuous)
a raster that contains cells of continuous values
cell size
– determines the resolution of a raster.
spatial reference –
a raster model must have a spatial reference information so they can align with other datasets in a GIS. The projection upon which raster data is able to be spatially related.
georeferenced raster –
a raster that has been processed to align with a projected coordinate system
remote sensing
– acquisition of information about an object without making physical contact with the object.
Landsat (NASA)
– an orbiting satellite that provides repeat images of the Earth’s surface. Latest landsat launched in 1999.
digital elevation model (DEM)
– a digital model with an array of uniformly spaced elevation data in raster format
digital orthophoto quad (DOQ)
a digitized image in which the displacement caused by the camera tilt and terrain relief has been removed from an aerial photograph.
digital raster graphic (DRG) –
a scanned image of a USGS topographic map.
USGS topographic map (7 1?2 minute quads)
map which stores topographic features at 250
dpi, uses 13 colors.
ESRI Grid –
format in which ArcGIS stores raster data
cell-by-cell encoding
– a raster data structure that stores cell value in a matrix by row and column
run-length encoding (RLE)
– a raster data structure that records the cell values by row and by group. A run-length encoded file is also called a run-length compressed file
quad tree (recursive decomposition)
– a raster data structure that divides rasters into a hierarchy of quadrants
header file
– file in which information about the raster, such as data structure, number of bands, and value for no data is stored.
data compression
– reduction of data volume, especially for raster data
MrSID
– a compression technique / format which allows for lossless and lossy compression (multiresolution seamless image database). Multiresolution means it can recall the image data at different resolutions or scales.
rasterization
– converting vector to raster
vectorization
converting raster to vector
Metadata –
provide information about geospatial data – an integral part of GIS data and are usually prepared and entered during the data production process
framework data-
common types of GIS data on the internet that many organizations regularly use for GIS activities, typically consist of seven basic layers
geodetic control
accurate positional framework for surveying and mapping
orthoimagery
recertified imagery such as orthophotos
Federal Geographic Data Committee (FGDC)
an interagency committee that leads development of policies, metadata standards, and training to support NSDI
National Spatial Data Infrastructure (NSDI)
– aimed at sharing of geospatial data throughout all levels of government, the private and nonprofit sectors, and the academic community.
U.S. Geological Survey (USGS)
– major provider of GIS data in the US.. offers national mapping and remotely sensed data, and to thematic data clearinghouses on biological, geological, and water resources data.
digital line graphs (DLGs) –
VECTOR digital representations of point, line, and area features from USGS quadrangle maps, at the scales of 1:24000, 1:100000, and 1:2,000,000
National Land Cover Data (NLDC)
– one of two datasets… 1992 includes 21 thematic classes compiled from thematic mapper imagery of the early 1990s. 2001 used the Landsat 7 ETM+ imagery to compile land cover data for all states and Puerto Rico.
digital elevation models (DEMs)
– digital elevation models available at three designated websites… include 7.5 minute, 15 minute and 30 minute DEMS.
National Elevation Dataset (NED) –
compiled by the USGS – provides 1:24000 scale of DEMS nationwide. A USGS program that uses a seamless system for delivering 1:24000 scale DEMS.
TIGER/Line Files (U.S. Census)
– offered by the US census bureau – extracts of geographic/ cartographic information from it’s MAF/TIGER database. Contain legal and statistical area boundaries such as counties, census tracts, and block groups, which can be linked to the census data, as well as roads, railroads, streams, waterbodies, etc.
Content Standard for Digital Geospatial Metadata (CSDGM)-
standards published by the FGDC which cover: identification, data quality, spatial data organization, spatial reference, entity and attribute, distribution, metadata reference, citation, time period, and contact. Have been revised in accordance with international standards.
Data conversion
– mechanism for converting GIS data from one format to another
Autocad’s DXF and DWG
a type of CAD file which can be translated to a GIS format (either shapefile or geodatabase) using ARCToolbox
GPS
is a space-based satellite navigation system that provides location and time information in all weather, anywhere on or near the Earth, where there is an unobstructed line of sight to four or more GPS satellites. Longitude, latitude, and elevation data for point locations made available through a navigational satellite system and a reciever
NAVSTAR (Navigation Satellite Timing and Ranging)-
a group of 24 satellites maintained by the US military which play a crucial role in GPS application.
Differential correction
– reducing noise errors mediated by a reference or base station
reference (base) station
– stations which allow for differential correction by using a known position that can calculate what the travel time of GPS signals should be.
Digitizing
– process of converting data from analog to digital format.
Scanning –
digitizing method which uses a scanner to concert an analog map into a scanned file in raster format, which is then concerted back to vector format through tracing.
Vectorization
– turns raster files into vector lines via a process called tracing.
on-screen (heads-up digitizing)
– manual digitizing on the computer monitor using a data source such as DOQ as the background.

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