<HTML dir=ltr><HEAD><TITLE>[Proj] geoid in Kalimantan, Indonesia</TITLE>
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<DIV dir=ltr><FONT face="Times New Roman" color=#000000 size=2>EGM96 is the best worldwide geoid available, but a Promark is a single-frequency receiver and is a poor candidate for the third component. I would estimate the vertical accuracy at about plus or minus 1 to 2 meters at best. A dual frequency receiver can get fairly reliable verticals because the two frequencies allow proper modeling of tropospheric effects - an impossibility with only a single frequency receiver. A short baseline differential technique (less than one kilometer with two simultaneous Promarks) is used for construction work, but certainly not even close to 10 kilometers muchless 30!</FONT></DIV>
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<FONT face=Tahoma size=2><B>From:</B> proj-bounces@lists.maptools.org on behalf of Frans Buschman<BR><B>Sent:</B> Wed 05-Mar-08 05:03<BR><B>To:</B> proj@lists.maptools.org<BR><B>Subject:</B> [Proj] geoid in Kalimantan, Indonesia<BR></FONT><BR></DIV>
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<P><FONT size=2>Hello,<BR><BR>In a coastal region in East Kalimantan, Indonesia, we measured with a GPS promark3 system height differences of several water level gauges with respect to the WGS-84 ellipsoide and datum. The stations are about 30 km apart and we think that the precision of the measurements is within 10 cm.<BR><BR>>From the water level gauges we want to see in what direction water should be flowing, so we want the want to derive the height differences with respect to a geoid. For Kalimantan no detailed geoid seems to exist, so I would like to convert measured height differences on the WGS-84 ellipsoide to height differences on a global geoid. Which geoid is best for this purpose and how can I make the conversion? Could you give an estimate of the error you make with this conversion?<BR><BR>Thanks!<BR>Frans<BR><BR>--<BR>______________________________________________________<BR>Frans Buschman (PhD student)<BR>Department of Physical Geography<BR>Institute for Marine and Atmospheric Research Utrecht<BR>Utrecht University<BR>P.O. box 80.115 / Heidelberglaan 2<BR>3508 TC Utrecht, the Netherlands<BR>Room 211 in Jan Zonneveldvleugel<BR>Phone: +31 - (0)30 2532778<BR>Fax: +31 - (0)30 2531145<BR>mail: f.buschman@geo.uu.nl<BR>______________________________________________________<BR><BR>_______________________________________________<BR>Proj mailing list<BR>Proj@lists.maptools.org<BR><A href="http://lists.maptools.org/mailman/listinfo/proj">http://lists.maptools.org/mailman/listinfo/proj</A><BR></FONT></P></DIV></BODY></HTML>