Geodatabase - ANSobject oriented spatial model, native data structure for ArcGIS, and is the
primary data format used for storing, editing, and managing geographic data.
Types of Geodatabases - ANSPersonal, File, Enterprise, workgroup
Types of Geodatabase datasets - ANSGeometric network, network dataset, parcel fabric, terrain
dataset, LAS dataset
Distance relations - ANSspecifies how far is the object away from the reference object.
Examples of distance relations - ANSat, nearby, in the vicinity;far away
Euclidean Distance - ANSexact distance between two coordinates sqrt((x1-x2)^2 + (y1+y2)^2))
Manhattan Distance - ANSvertical plus horizontal distance - abs(x1-x2)+abs(y1+y2)
Internal Direction - ANSwhere an object is located inside the reference object
External Direction - ANSwhere the object is located outside of the reference object
Spatial Model - ANSbasic properties and processes for a set of spatial features
Vector Data - ANScomposed of points, lines, polygons
Raster - ANScomposed of rectangular arrays of regularly spaced square grid cells and each cell
has a value (attribute)
Pixel - ANSsmallest resolvable piece of scanned image-pixel is always a cell but a cell is not
always a pixel.
Temporal - ANSthe world is constantly changing. A static map can only show one time period at
once.
Imprecision - ANSall data is taken from a 3D globe and transferred to a 2D surface through
spatial transformations (projections and datum's) which causes distortions with the data.
Uncertainty - ANSThe GIS data was created/collected at a certain point of time, may already be
out of data.
, Geoid - ANSthe shape of the earth as defined by mean sea level and affected by topographic
and gravitational factors. What the shape of the earth would be if there were only seas and no
continents.
Reference Ellipsoid - ANSa mathematically defined surface that approximates the geoid, the
truer figure of the earth, or other planetary body.
Oblate ellipsoid - ANSfits the geoid to a first order approximation-formed when an ellipse is
rotated about its minor axis
Sphere - ANSAs can be seen from dimensions of the Earth ellipsoid, the semi-major axis 'a' and
the semi-minor axis 'b' differ only by a bit more than 21 kilometeres
Spatial reference (SRS) or Coordinate system (CRS) - ANSis coordinate-based local, regional
or global system used to locate geographical entities
International Terrestrial Reference System (ITRS) - ANSThree-dimensional coordinate system
with a well-defined origin (the center of mass of the Earth) and three orthogonal coordinate axes
(X,Y,Z)
Map projection - ANStransforming coordinates from a curved earth to a flat map
Horizontal Datum - ANSmodel of the earth as a spheroid (2 components, reference ellipsoid and
a set of survey points both the shape of the spheroid and its position relative to the earth)
Vertical Datum - ANSreference point for elevations of surfaces and features on the Earth-could
be based on tidal, sea levels, gravimetric, based on a geoid
What kinds of things can be distorted with different map projections? - ANSDistance, direction,
shape, area
Datum - ANSModel of the earth as a spheroid
Geodetic datum - ANSa set of control points whose geometric relationships are known, either
through measurement or calculation.
NAVD88 - ANSgravity based geodetic datum in North America
North American Datum of 1927 (NAD 1927) - ANSbased on the Clarke 1866 spheroid
North American Datum of 1983 (NAD 1983) - ANSbased on the more accurate GRS 1980
spheroid
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