FUNDAMENTAL SURVEYING Geodesy and Map Projections 3

Question 1

What is GEOID18 (or GEOID12B) used for?

Accepted Answer

Converting between ellipsoid heights (GPS) and orthometric heights (NAVD88)

Answer

Converting NAD83 horizontal coordinates to NAD27

Answer

Converting UTM coordinates to State Plane

Answer

Determining magnetic declination

Question 2

The semi-major axis of the GRS80 ellipsoid (used for NAD83) is approximately:

Accepted Answer

6,378,137 m

Answer

6,356,752 m

Answer

6,371,000 m

Answer

6,400,000 m

Question 3

What is the relationship between geographic (geodetic) latitude and geocentric latitude?

Accepted Answer

Geographic latitude is larger than geocentric latitude except at poles and equator

Answer

They are identical on any ellipsoid

Answer

Geocentric latitude is always larger

Answer

They differ only at the poles

Question 4

An 'equal-area' map projection preserves which property?

Accepted Answer

Areas of regions

Answer

Angles and shapes

Answer

Distances from the center

Answer

Compass directions

Question 5

What is the 'Helmert transformation' used for in geodesy?

Accepted Answer

Transforming coordinates between two geodetic datums using translation, rotation, and scale parameters

Answer

Converting ground distances to grid distances

Answer

Adjusting a GPS baseline

Answer

Computing geoid undulation values

Question 6

What is the 'deflection of the vertical'?

Accepted Answer

The angular difference between the direction of gravity (plumb line) and the normal to the reference ellipsoid

Answer

The tilt of a survey instrument off-level

Answer

The angle between magnetic and true north

Answer

The refraction correction for vertical angles