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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Sextant Positions versus Map Datums
From: Jared Sherman
Date: 2002 Jan 20, 9:22 PM
From: Jared Sherman
Date: 2002 Jan 20, 9:22 PM
>> Does your conversion program make that conversion ? << No Bill, the program they supplied does only limited conversions. Unless the celestial system is the same as UTM? Here's a quote from the docs on it: "$ The U.S. Army Topographic Engineering Center (TEC) created a more comprehensive program called Corpscon (Corps Convert), which is based on Nadcon, Vertcon and Geoid96. In addition to transformations between NAD83 and NAD27 geographical coordinates, Corpscon also converts between State Plane Coordinates Systems (SPCS), Universal Transverse Mercator (UTM) and geographical coordinates; thus eliminating several steps in the total process of converting between SPCS27, SPCS83, UTM27, and UTM83. Inputs can be in either geographic or SPCS/UTM coordinates (SPCS27 X and Y or SPCS83 Northing and Easting). This program can also be used to convert between state plane, geographic, and UTM coordinates on the same datum. Corpscon will convert orthometric and ellipsoidal heights in Geographic, State Plane and UTM coordinate systems. $ Corpscon allows conversions based on U.S. Survey and International Feet. As of 1997, 19 states have specified, by statute, units of measure for grid coordinates as follows: U.S. Survey Foot - California, Colorado, Connecticut, Idaho, Indiana, Kentucky, Maryland, Massachusetts, Mississippi, New Mexico, New York, North Carolina, Oklahoma, Pennsylvania, Tennessee, Texas, Washington and Wisconsin. International Survey Foot - Arizona, Michigan, Montana, North Dakota, Oregon, South Carolina and Utah. $ Corpscon 5.0 includes conversions based on High Accuracy Regional Networks (HARN's). " ====================================== Incidentally--carefully locating the Jones Beach Water Tower on my 1985 NAD27 1:20,000 chart shows it to be located 0.3nm away from the current position of the tower that is given in the http://www.ngs.noaa.gov/cgi-bin/ds_mm.prl reference list. So infosofar as that particular area, more than 1/10th of my position error appears to come from the landmarks being shown in the wrong place. 1/10th down, 9/10th's more to go.It will be interesting to take a (pre-WAAS) GPS to the three area benchmarks that are accessible and see how well it compares.