Conceptual Foundations

Question 1

Georeferencing

Answer 1

Associating a map (such as a pdf without spatial information), or image (such as an aerial image without spatial information), with spatial locations.

Question 2

Control Points

Answer 2

Consisting of multiple points, points come in pairs that match the spatial location with a point on an unreferenced image or map.

Question 3

Spatial Reference System (SRS)/ Coordinate Reference System (CRS)

Answer 3

A coordinate-based local, regional, or global system is used to locate geographical entities.

Question 4

International Terrestrial Reference System (ITRS)

Answer 4

It’s 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).

Question 5

Map Projection

Answer 5

transforming coordinates from a curved earth to a flat map

Question 6

UTM

Answer 6

Universal Transverse Mercator - a global coordinate system. UTM zones are 6 degrees

Question 7

Horizontal Datum

Answer 7

Model of the Earth as a spheroid ( 2 components, reference ellipsoid and a set of survey points, both the shape of the spheroid and the features on the Earth)

Question 8

NAVD88

Answer 8

Gravity-based geodetic datum in North America

Question 9

Geodetic Datum

Answer 9

A set of control points whose geometric relationships are known, either through measurement or calculation.

Question 10

Vertical Datum

Answer 10

reference point for elevations of surfaces and features on the Earth

Question 11

WGS84

Answer 11

World Geodetic System, reference coordinate system used by the Global Positioning System (GPS).

Question 12

SRID Integer

Answer 12

spatial reference system id numbers, including EPSG codes defined by the International Association of Oil and Gas Producers

Question 13

Four Distortions

Answer 13

Angle, Area, Direction, Shape (A SAD)

Question 14

Mercator Projection

Answer 14

Preserve shape and direction, the area gets distorted, projecting earth onto a cylinder tangent to a meridian.

Question 15

Azimuthal Equidistant

Answer 15

planar (tangent), used for air route distances; Distance measured from the center is true; Distortion of other properties increases away from the center point

Question 16

Cylindrical Equal-area Projection

Answer 16

preserves area; shape and distance get distorted near the upper and lower regions of the map; straight meridians and parallels; meridians are equally spaced and the parallels are unequally spaced

Question 17

Conic Projection

Answer 17

preserves directions and the area in limited areas; Distorts distances and scales except along standard parallels; Generated by projecting a spherical surface onto a cone

Question 18

Choosing projections: based on latitude

Answer 18

Latitude: low -> conical projection; polar regions –> azimuthal planar projection

Question 19

Choosing projections: based on the extent

Answer 19

Extent: Broad in East-West –> conical; Broad in North-South –> Cylindrical projection

Question 20

Choosing projection: based on thematic

Answer 20

If you are doing an analysis that compares the different values in a different location, typically an equal-area projection will be used.

Question 21

Discrete features

Answer 21

a feature that has a definable boundary, begins and ends, for example a highway or a lake

Question 22

Continuous phenomena

Answer 22

Each location is a measure of something, including the measure of concentration level, and the measure of a value in terms of a fixed point, such as elevation

Question 23

Geoid

Answer 23

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 wind or tides; Used to reference heights, by registering the ocean’s water level as coastal places using the tide gauges (how the sea level is decided).

Question 24

Reference Ellipsoid

Answer 24

A mathematically defined surface that approximates the geoid, the truer figure of the Earth, or other planetary body

Question 25

Oblate Ellipsoid

Answer 25

It fits the geoid to a first-order approximation, formed when an ellipse is rotated about its minor axis.

Question 26

Sphere (Earth)

Answer 26

Earth’s semi-major axis A and semi-minor axis B differ only by a bit more than 21 km.

Question 27

First (direct) geodetic problem

Answer 27

Given a point (in terms of its coordinates) and the direction (azimuth) and distance from that point to a second point, determine (the coordinate of) that second point

Question 28

Second (inverse) geodetic problem

Answer 28

Given two points, determine the azimuth and length of the line that connects them

Question 29

Geomatics

Answer 29

Science and technology of gathering, analyzing, interpreting, distributing, and using geographic information (including surveying, mapping, remote sensing, GIS, GPS)