Certified Photogrammetrist Geodesy & Map Projections

Question 1

NAD 83 coordinates are referenced to which ellipsoid?

Accepted Answer

GRS 80

Answer

NAD 83 uses the GRS 80 ellipsoid, while NAD 27 used Clarke 1866.

Question 2

A GNSS point has ellipsoid height h = 152.40 m and geoid height N = -30.10 m. What is its orthometric height H?

Accepted Answer

182.50 m

Answer

H = h - N = 152.40 - (-30.10) = 182.50 m.

Question 3

What scale factor is applied at the central meridian of every UTM zone?

Accepted Answer

0.9996

Answer

UTM uses a central meridian scale factor of 0.9996 to balance distortion across the 6-degree zone.

Question 4

Which projection is typically used for State Plane zones that extend mainly east-west?

Accepted Answer

Lambert Conformal Conic

Answer

Lambert Conformal Conic keeps scale error low along its standard parallels, which suits east-west zones.

Question 5

What is the deflection of the vertical?

Accepted Answer

The angle between the plumb line and the ellipsoid normal

Answer

Deflection of the vertical is the angle between the direction of gravity (plumb line) and the ellipsoid normal at a point.

Certified Photogrammetrist Practice Test