You are currently viewing an archived version of Topic Horizontal (Geometric) Datums.
If updates or revisions have been published you can find them at Horizontal (Geometric) Datums.

Learning Objectives:

Discuss appropriate applications of the various datum transformation options

Explain the difference between NAD 27 and NAD 83 in terms of ellipsoid parameters

Outline the historical development of horizontal datums

Explain the difference in coordinate specifications for the same position when referenced to NAD 27 and NAD 83

Explain the rationale for updating NAD 27 to NAD 83

Explain why all GPS data are originally referenced to the WGS 84 datum

Identify which datum transformation options are available and unavailable in a GIS software package

Define “horizontal datum” in terms of the relationship between a coordinate system and an approximation of the Earth’s surface

Describe the limitations of a Molodenski transformation and in what circumstances a higher parameter transformation such as Helmert may be appropriate

Determine the impact of a datum transformation from NAD 27 to NAD 83 for a given location using a conversion routine maintained by the U.S. National Geodetic Survey

Explain the methodology employed by the U.S. National Geodetic Survey to transform control points from NAD 27 to NAD 83

Perform a Molodenski transformation manually

Use GIS software to perform a datum transformation

You are currently viewing an archived version of Topic Horizontal (Geometric) Datums. If updates or revisions have been published you can find them at Horizontal (Geometric) Datums.

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