Conceptual Foundations

Question 1

Distance

Answer 1

how far the object is from the reference object

Examples: at, nearby, in the vicinity, far away

Question 2

Euclidean Distance

Answer 2

exact distance between two coordinates, straight line sqrt((x1-x2)^2 + (y1+y2)^2))

Question 3

Manhattan Distance

Answer 3

vertical plus horizontal distance, x and y plane abs(x1-x2) + abs(y1-y2)

Question 4

Internal Direction

Answer 4

where an object is located inside a reference object

Examples: left, on the back, athwart, abaft

Question 5

External Direction

Answer 5

where the object is located outside of the reference object

Examples: on the right of, behind, in front of, abeam, astern

Question 6

Spatial Model

Answer 6

Basic Properties and process for a set of spatial features

Question 7

Vector

Answer 7

points, lines, polygons

Question 8

Raster

Answer 8

composed of rectangular arrays of regularly spaced square grid cells and each cell has a value (attribute)
Examples: elevation, soil pH, salinity of a body of water

Question 9

Pixel

Answer 9

smallest resolvable piece of scanned image. All pixels are cells

Question 10

Geodatabase

Answer 10

object oriented spatial model (feature class, feature dataset, nonspatial tables, topology, relationship classes, geometric networks

Question 11

Temporal

Answer 11

Time. the world is constantly changing. Multiple Maps can be created to show the changes or somehow superimpose multiple time period pieces of data on a map

Question 12

Imprecision

Answer 12

all data is taken from a 3D globe and transferred to a 2D surface through spatial transformations (projections and datums) which causes distortions to the data

Question 13

Uncertainty

Answer 13

The GIS data was created/collected at a certain point of time, may already be out of date

Question 14

Geoid

Answer 14

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 tides and winds.
Used to reference heights, by registering ocean’s water level at coastal places using tide gauges, this is how mean sea level is determined

Question 15

Reference Ellipsoid

Answer 15

a mathematically defined surface that approximates the geoid, the truer figure of the Earth or other planetary body. preferred surface on which geodetic network computations are performed such as longitude, latitude and elevation

Question 16

Oblate Ellipsoid

Answer 16

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

Question 17

Sphere

Answer 17

As can be seen from the dimensions of the Earth ellipsoid, the semi-major axis a and the semi-minor axis b differ only by a bit more than 21 kilometres

Question 18

International Terrestrial Reference System (ITRS)

Answer 18

three-dimensional coordinate system with a well defined origin ( center of the mass of the Earth) and three orthogonal coordinate axes (X,Y,Z)
X axis - oriented toward Greenwich meridian
Z axis - oriented toward Earth’s North Pole

Question 19

Geodetic Datums

Answer 19

geocentrically positioned with respect to the center of mass of the Earth – WGS84, ITRF2000

Question 20

Horizontal Datum

Answer 20

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

Question 21

Vertical Datum

Answer 21

reference point for elevations of surfaces and features on the Earth - could be based on tidal, seas levels, gravimetric, based on a geoid

Question 22

Map Projection

Answer 22

Transforming coordinates from a curved earth to a flat map

Question 23

NAVD88

Answer 23

gravity based geodetic datum in North America

Question 24

WGS 84

Answer 24

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

Question 25

SRID Integer

Answer 25

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

Distortions, Distance,Direction,Shape,Area

Question 26

Mercator

Answer 26

Preserves shape and direction, area gets distorted - projecting earth onto a cylinder tangent to a meridian

Question 27

Azimuthal Equidistant

Answer 27

planar tangent - used for air route distances - distances measured from the center are true - distortion of other properties increases away from the center point

Question 28

Cylindrical equal-area projections

Answer 28

preserves area, shape and distance gets 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 29

Conic Projections

Answer 29

preserves directions and areas in limited areas - distorts distances and scale except along standard parallels - generated by projecting a spherical surface onto a cone

Question 30

Latitude

Answer 30

low-latitude areas ( near equator) use a conical projection; Polar regions use a azimuthal planar projection

Question 31

Extent

Answer 31

Broad in East-West (USA) use a conical projection; Broad in North-South (Africa) use a transverse-case cylindrical projection

Question 32

Thematic

Answer 32

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

Question 33

Spatial Reference System

Answer 33

coordinate-based local, regional or global system used to locate geographical areas