PS Geodetic Datums & Coordinate Systems 2

Question 1

What is the ellipsoidal flattening (f) of GRS80, the ellipsoid underlying NAD83?

Accepted Answer

1/298.257222101

Answer

GRS80 has a flattening of 1/298.257222101, making it nearly identical to WGS84's 1/298.257223563.

Question 2

Which datum adjustment method was used to establish NAD83 and involved over 250,000 control points?

Accepted Answer

Minimum-constraint least squares adjustment

Answer

NAD83 was established using a minimum-constraint least squares adjustment holding one point (Meades Ranch area) and one azimuth fixed.

Question 3

In the Universal Transverse Mercator (UTM) system, what is the width of each zone in degrees of longitude?

Accepted Answer

6°

Answer

UTM divides the world into 60 zones, each spanning 6° of longitude, numbered 1 through 60 eastward from 180°.

Question 4

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

Accepted Answer

0.99960

Answer

The UTM central meridian scale factor is 0.9996, reducing distortion by distributing scale error across the zone width.

Question 5

A geoid height (N) of +35 meters at a point means the geoid is located how relative to the ellipsoid?

Accepted Answer

35 m above the ellipsoid

Answer

Positive geoid height (N) indicates the geoid surface lies above the reference ellipsoid by that amount.

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