What is the difference between Geiod 1999 and Geiod 2003 for Hawaii
April 13 2009 |
What is the difference between Geiod 1999 and Geiod 2003 for Hawaii?
Mapping Center Answer:
The GEOID 1999 model computes hybrid geoid undulations (an old term for the name for the separation N between the geoid and the reference ellipsoid of the Earth) between NAD 83 GPS derived ellipsoid heights, which is NAD 83 (HARN), and NAVD 88 Helmert orthometric heights. Areas covered are the conterminous United States, Hawaii, Alaska, Puerto Rico and the American Virgin Islands. More information about this model and the next model is available at NOAA/NGS/GEOID website.
The GEOID 2003 is a refined model of the GEOID 1999 model. In regards to Hawaii, this GEOID 2003 is based on 11 thousand GPS observations for better accuracy than the previous model where 6 thousand GPS observations were used. The model doesn't replace the accuracy that surveyors might achieve using differential leveling, but if you don't require centimeter of less vertical accuracy, then the GEOID 2003 will do the job.
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