Week 6: Georeferencing and projections

Question 1

Enclave

Answer 1

Territory, or part of a territory that is entirely surrounded by the territory of one other state

Question 2

Geo referencing needs to be

Answer 2

Unique, have a shared meaning that is persistent through time

Question 3

Latitude/longitude is a

Answer 3

Geographic unprojected coordinate system

Question 4

Georeferencing is

Answer 4

The process of aligning digital maps or images with real-world geographic locations, essentially tying them to a known coordinate system

Question 5

Four common types of geo references

Answer 5

1. Place names (nominal)
2. Postal codes / addresses (ordering)
3. Cadastral (metric, land parcels)
4. Coordinates (metric, lat/long, UTM)

Question 6

Coordinate systems are used to

Answer 6

Identify locations of features on maps that are on the earths surface

Question 7

Coordinate systems are based on

Answer 7

Measurements of displacement from a given location (origin)

Question 8

Coordinate systems allow us to

Answer 8

Integrate map feature types for the same area in the same projection and do GIS-based spatial analysis

Question 9

Two types of coordinate systems

Answer 9

1. Global (geographic unprojected coordinate system
2. Plane (projected coordinate system)

Question 10

All projected coordinate systems have

Answer 10

Distortions

Question 11

Components to create a coordinate system

Answer 11

1. Projection
2. Datum
3. Origin point
4. Units

Question 12

Why is there the usage of planar (cartesian) coordinate systems

Answer 12

1. Flat paper maps are simpler than curved mathematically
2. Units are the same for both X and Y

Question 13

Most widely used projected coordinate system

Answer 13

Transverse mercator

Question 14

Process of creating a (metric) geo referencing system

Answer 14

1. Approximate the earth’s surface that other processes can reference
   (spheroid, ellipsoids, geoids, datums, origin)
2. Transform semi-spherical surface of the earth to flat (2-D) map (map
   projections with units)
3. Use a co-ordinate system that allows features to be located with reference
   to the projected map

Question 15

Why are geoids important

Answer 15

1. A reference surface for vertical measurements
2. Ellipsoids do not account for earths complex topography

Question 16

Characteristics of an equipotential surface based on gravitational irregularities

Answer 16

1. Equal gravity surface extends through the continents
2. Approximates mean sea level (w/o tides, winds, waves or swell)
3. surveying is based on the concept of a plane perpendicular to the gravity surface of the earth (i.e the direction of a plumb bob pointing to earhts centre of mass

Question 17

Why are ellipsoids important

Answer 17

A reference surface for horizontal measurements

Question 18

Latitude/longitude and plane coordinates derived from latitude/longitude are referenced to

Answer 18

A given ellipsoid

Question 19

Definition of a datum

Answer 19

A system for anchoring an ellipsoid to known locations (surveyed control points) on the earth

Question 20

Characteristics of a datum

Answer 20

1. A reference ellipsoid closely fitting the local geoid is tied to an initial point
2. Or if a global datum (WGS 84), a close fit for the entire earth is sought
3. A basepoint is assigned base coordinates as an anchor, and from there all other coordinates are calculated upon the reference ellipsoid