Lecture 3: Coordinate systems

Question 1

Geographic figure definition

Answer 1

Physical shape given by the terrain

Question 2

Geoid definition

Answer 2

1. An equipotential surface
2. Approximates mean sea level

Question 3

Reference ellipsoid definition

Answer 3

1. A convenient computational surface
2. Ellipsoid: latitude > longitude
3. Flattening f = (latitude-longitude)/longitude

Question 4

Coordinate system transformation process

Answer 4

Actual earth - 3D Earth Model (ellipsoid or sphere) - Plane Surface (projection) - Map (e.g cadastral, engineering plan, topo map, chart)

Question 5

Two datum surfaces and one projection surface in surveying

Answer 5

Datum surfaces: Coordinate frame, Reference ellipsoid
Projection surface: Projection

Question 6

The three primary map types

Answer 6

1. Conic
2. Azimuthal
3. Mercator

Question 7

What are map projections attempts at

Answer 7

Attempts to portray the surface of the earth on a flat surface

Question 8

An implication to projections is that survey measurements (directions, distances) require

Answer 8

Observation corrections

Question 9

Three primary observation corrections

Answer 9

1. Line scale factor
2. Arc to chord corrections
3. Reduction to the ellipsoid

Question 10

The mapping process creates distortion in

Answer 10

1. Shapes and angles
2. Distance
3. Direction
4. Scale
5. Area

Question 11

The larger the map, the greater the

Answer 11

Distortion

Question 12

The four coordinate types

Answer 12

1. 3D Cartesian coordinates
2. 3D Geodetic coordinates
3. 2D Grid coordinates
4. 1D Geodetic coordinates

Question 13

What parameters do 3D Cartesian Coordinates use

Answer 13

XYZ

Question 14

What parameters do 3D Geodetic coordinates use

Answer 14

Latitude, longitude and height (ellipsoid parameters)

Question 15

What parameters do 2D grid coordinates use

Answer 15

Northing and Easting (projection parameters)

Question 16

What parameters do 1D geodetic coordinates use

Answer 16

Height and elevations (MSL, geoid ellipsoid seperation relationships)

Question 17

3D geodetic coordinates require the definition of

Answer 17

An ellipsoid

Question 18

Whats required to define an ellipsoid

Answer 18

1. Semi-axis major (m)
2. Inverse flattening (1/f)

Question 19

3D cartesian coordinates assume earth is

Answer 19

Centred and fixed

Question 20

Both cartesian and geodetic coordinates are geometrically

Answer 20

Consistent

Question 21

When are 3D Cartesian coordinates commonly used

Answer 21

1. GNSS positioning - satellite orbits, SPP (pseudorange positions), RTK (carrier-phase vectors)
2. Remote imagery
3. Lidar data sets

Question 22

When are 3D Geodetic coordinates commonly used

Answer 22

1. Navigation - sea and air
2. Global and navigation survey networks

Question 23

Most common/relevant examples of 2D dimensional coordinates

Answer 23

1. Transverse Mercator
2. Lambert
3. NZ map grid

Question 24

The projection parameters required in 2D Dimensional coordinates

Answer 24

1. Latitude and longitude of origin
2. False Easting and Northing
3. Central meridian scale factor

Question 25

When are 2D dimensional coordinates commonly used

Answer 25

1. Most field surveying 2. Topographical maps - e.g NZTM, Topo50 (1:50,000) 3. Bathymetric charts (also often used in geodetic coordinates) 4. Cadastral maps - e.g meridional circuits 5. Engineering projects - typically based on a local grid and can be plane grid if project is not too large

Question 26

In 1D dimensional coordinates, the Ellipsoid/geodetic height is calculated how

Answer 26

Orthometric height (approx mean sea level) + Geoid and ellipsoid height difference

Question 27

Coordinates are mathematically ____

Answer 27

Related to each other

Question 27

By defining a coordinate frame, we can give the point ____ coordinates

Answer 27

Cartesian coordinates

Question 28

By defining an ellipsoid, we can give the point ____ coordinates

Answer 28

Geodetic coordinates

Question 29

By defining a projection, we can give the point ____ coordinates

Answer 29

Grid/Projection coordinates

Question 30

From lines of latitude, parallels are

Answer 30

East/west lines which are parallel with the equator

Question 31

From lines of longitude, parallels are

Answer 31

North/South lines that converge through the poles and are perpendicular to the equator

Question 32

What is the origin for parallels

Answer 32

The pole of rotation

Question 33

What is the origin for Meridians

Answer 33

The centre of the earth

Question 34

Accessing and downloading geodetic mark data is available at

Answer 34

LINZ geodetic database

Question 35

3D equals 2D plus 1D. True or false

Answer 35

False

Question 36

A geodetic datum is

Answer 36

A customized reference and computational surface for 2D and/or 3D coordinates

Question 37

The worlds geodetic datum

Answer 37

WGS84

Question 38

New zealands terrestrial triangulation (2d) geodetic datum

Answer 38

NZGD1949

Question 39

New zealands space based (3d) geodetic datum

Answer 39

NZGD2000

Question 40

A vertical datum is

Answer 40

A customized reference surface for 1D coordinates

Question 41

Dunedins vertical datum

Answer 41

DunedinVD1958 - classical mean sea level (MSL) based on levelling

Question 42

New Zealands vertical datum

Answer 42

NZVD2016 - equipotential surface based on gravity

Question 43

Global datum characteristics

Answer 43

1. Geocentric 2. Global network 3. Reference ellipsoid 4. Defined using space-based technology e.g GNSS

Question 44

Local datum characteristics

Answer 44

1. Non-geocentric 2. Single origin station (usually) 3. Reference ellipsoid 4. Defined using triangulation methodology

Question 45

Most common ellipsoids

Answer 45

1. International 1924 2. WGS72 3. WGS84 4. GRS80

Question 46

The geoid is a representation of the surface of the earth that it would assume if

Answer 46

The sea covered the earth (i.e no topography

Question 47

Geoids are thought of as a surface of equal

Answer 47

Gravitational potential and mean sea level, however sea level isnt flat and has topography

Question 48

Geoids can be defined as

Answer 48

The shape a fluid earth would have if it had the gravity field of the earth

Question 49

Geoids are roughly the mean sea level surface, excluding

Answer 49

Dynamic effects such as waves and tides

Question 50

Geoid highs are gravity ____

Answer 50

Highs (and vice versa)

Question 51

Vector/vertical gravity is perpendicular to

Answer 51

The geoid

Question 52

Gravity will be deflected towards a dense body because

Answer 52

Fluid is attracted toward a denser body and therefore raises its surface