PS Geodetic Datums & Coordinate Systems 3

Question 1

What is the approximate horizontal shift between NAD27 and NAD83 coordinates in the contiguous United States?

Accepted Answer

10 to 100 meters

Answer

NAD27 to NAD83 datum shifts in CONUS typically range from about 10 to 100 meters depending on location.

Question 2

What does the acronym ITRF stand for in the context of global geodetic reference frames?

Accepted Answer

International Terrestrial Reference Frame

Answer

ITRF (International Terrestrial Reference Frame) is maintained by the IERS and represents the most precise global geodetic reference system.

Question 3

In SPCS 83, the false easting assigned to the central meridian of a Transverse Mercator zone is typically:

Accepted Answer

200,000 meters

Answer

SPCS 83 TM zones are assigned a false easting of 200,000 meters to keep all coordinates positive.

Question 4

Which of the following best describes an orthometric height?

Accepted Answer

Height above the geoid measured along the plumb line

Answer

Orthometric height is the distance from the geoid to the point, measured along the curved plumb line (direction of gravity).

Question 5

The Transverse Mercator projection is conformal, which means it preserves:

Accepted Answer

Shape (angles) locally

Answer

Conformal projections preserve local angles and shapes, meaning small figures on the map are geometrically similar to those on the ellipsoid.

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