DM-52 - Horizontal datums
- 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
DM-51 - Vertical datums