GISP Study Guide with Complete Solutions
Georeferencing - Answer️️ -101- associating a map or image with spatial
location
control points - Answer️️ -101- points come in pairs that match the spatial
location with a point on an unreferenced image or map
Spatial Reference Systems (SRS) - ...
Georeferencing - Answer✔️✔️-101- associating a map or image with spatial
location
control points - Answer✔️✔️-101- points come in pairs that match the spatial
location with a point on an unreferenced image or map
Spatial Reference Systems (SRS) - Answer✔️✔️-101- coordinate based local,
regional, or global system used to location geographical entities (aka
Coordinate Reference System (CRS))
Coordinate Reference System (CRS) - Answer✔️✔️-101- coordinate based
local, regional, or global system used to location geographical entities (aka
Spatial Reference Systems (SRS))
International Terrestrial Reference System (ITRS) - Answer✔️✔️-101- a three-
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 - Answer✔️✔️-101- transforming coordinated from a curved
surface (Earth) to a flat map
Horizontal datum - Answer✔️✔️-101- model 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 - Answer✔️✔️-101- reference point for measuring elevations
NAVD88 - Answer✔️✔️-101- Gravity based geodetic datum in North
America
WGS 84 (World Geodetic System) - Answer✔️✔️-101- reference coordinate
system used by the Global Positioning System (GPS)
SRID integer - Answer✔️✔️-101- Spatial reference system id numbers,
including EPSG codes defined by the International Association of Oil and
Gas Producers
types of distortion - Answer✔️✔️-101- Distance, Direction, Shape, Area
(sometimes bearing and scale)
Mercator Projection- distortions - Answer✔️✔️-101- preserves shape and
direction, area gets distorted
Mercator Projection - Answer✔️✔️-101- projecting the Earth onto a cylinder
tangent to a meridian
Azimuthal Projection- distortions - Answer✔️✔️-101- distance from center is
true, other properties distort with distance
Azimuthal Projection - Answer✔️✔️-101- planar or tangent (meaning they
are formed when a flat piece of paper is placed on top of the globe and a
light source projects the surrounding areas on to a map.) Either the North
Pole or the South pole is orientated at the center of the map, giving the
viewer an impression of looking up or down at Earth.
Cylindrical Projection- distortions - Answer✔️✔️-101- preserve area and
shape, distance gets distorted, especially on upper and lower regions of the
map
meridians are equally spaced while parallels are not
Conical Projection- distortions - Answer✔️✔️-101- preserves direction and
area in limited areas, distorts distance and scale except along standard
parallels
Conic Projections - Answer✔️✔️-101- mapped to equally spaced lines by
projecting a spherical surface onto a cone
Choosing a Projection- Low LATITUDE, (near Equator) - Answer✔️✔️-101-
use conical projection
Choosing a Projection- High LATITUDE, Polar Regions - Answer✔️✔️-101-
use azimuthal planar projections
Choosing a Projection- EXTENT, broad East-West (e.g. USA) - Answer✔️✔️-
101- use conical projection
Choosing a Projection- EXTENT, broad North-South (e.g. Africa) -
Answer✔️✔️-101- use transverse-case cylindrical projection
Choosing a Projection- THEMATIC, analysis that compares different
values in different locations - Answer✔️✔️-101- use an equal-area projection
Discrete features - Answer✔️✔️-102- feature has a definable boundary
(think, "vector")
continuous phenomena - Answer✔️✔️-102- each location is a measure of
something, often temperature or elevation (think "raster", but not always)
Geoid - Answer✔️✔️-103- the shape that the surface of the oceans would
take under the influence of Earth's gravitation and rotation alone (absent of
the influence of wind or tide)
Mean Sea Level (MSL) - Answer✔️✔️-103- is determined by referencing the
geoid model which registers ocean's water level at coastal places using tide
gauges
Reference Ellipsoid - Answer✔️✔️-103- is a mathematically defined surface
that approximates the geoid (a truer model of shape that geoid)
oblate ellipsoid - Answer✔️✔️-103- fits the geiod model to a first order
approximation
formed when an ellipse is rotated about its minor axis (The shape of the
Earth, slightly bulging at the Equator.)
sphere - Answer✔️✔️-103- can be seen from dimensions of the Earth
ellipsoid
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