[Proj] geoid in Kalimantan, Indonesia

[Clifford J Mugnier]

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!
 
Clifford J. Mugnier, C.P., C.M.S.
LSU Student ASCE Chapter Faculty Advisor
and
National Director (2006-2008),
Photogrammetric Applications Division
American Society for Photogrammetry and Remote Sensing 
and 
Chief of Geodesy,
CENTER FOR GEOINFORMATICS 
Department of Civil Engineering 
CEBA 3223A
LOUISIANA STATE UNIVERSITY 
Baton Rouge, LA  70803
Voice and Facsimile:  (225) 578-8536 [Academic] 
Voice and Facsimile:  (225) 578-4474 [Research] 
Honorary Life Member of the 
Louisiana Society of Professional Surveyors 
Member Emeritus of the ASPRS 
Member of the Americas Petroleum Survey Group
======================================================
http://www.asprs.org/resources/GRIDS/
======================================================

________________________________

From: proj-bounces at lists.maptools.org on behalf of Frans Buschman
Sent: Wed 05-Mar-08 05:03
To: proj at lists.maptools.org
Subject: [Proj] geoid in Kalimantan, Indonesia



Hello,

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.

>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?

Thanks!
Frans

--
______________________________________________________
Frans Buschman (PhD student)
Department of Physical Geography
Institute for Marine and Atmospheric Research Utrecht
Utrecht University
P.O. box 80.115 / Heidelberglaan 2
3508 TC Utrecht, the Netherlands
Room 211 in Jan Zonneveldvleugel
Phone: +31 - (0)30 2532778
Fax: +31 - (0)30 2531145
mail: f.buschman at geo.uu.nl
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