<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv=Content-Type content="text/html; charset=us-ascii">
<meta name=Generator content="Microsoft Word 12 (filtered medium)">
<!--[if !mso]>
<style>
v\:* {behavior:url(#default#VML);}
o\:* {behavior:url(#default#VML);}
w\:* {behavior:url(#default#VML);}
.shape {behavior:url(#default#VML);}
</style>
<![endif]-->
<title>[Proj] geoid in Kalimantan, Indonesia</title>
<style>
<!--
/* Font Definitions */
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Tahoma;
panose-1:2 11 6 4 3 5 4 4 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman","serif";}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
p
{mso-style-priority:99;
mso-margin-top-alt:auto;
margin-right:0cm;
mso-margin-bottom-alt:auto;
margin-left:0cm;
font-size:12.0pt;
font-family:"Times New Roman","serif";}
span.EmailStyle18
{mso-style-type:personal-reply;
font-family:"Calibri","sans-serif";
color:#1F497D;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page Section1
{size:612.0pt 792.0pt;
margin:72.0pt 72.0pt 72.0pt 72.0pt;}
div.Section1
{page:Section1;}
-->
</style>
<!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body lang=EN-US link=blue vlink=purple>
<div class=Section1>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Frans,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I tend to agree with Clifford. As a surveyor myself and having
used the ProMark3’s in anger I can say the manufacturers specifications leave
the whole “accuracy depending on atmosphere” open to
interpretation. When I read your post I assumed you’d performed a static
differential survey with a pair of ProMarks to build a network including your
tide gauges. If you have simply positioned your Promark above the tide gauge and
observed for 20 or 30 minutes then your results are likely to be poor.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I have always used a rule of thumb that the vertical accuracy of
a GPS is about 2.5-3 time worse than the quoted horizontal accuracy in RELATIVE
terms. What you’re trying to do is perform a gravity survey in ABSOLUTE
terms. I’ve done countless surveys for irrigation over vast tracts of
land. They key here is you need an accurate vertical geoidal model upon which
to base your survey. Typically I’ve had the benefit of connecting to
existing bench marks that were leveled with spirit or optical leveling techniques.
Since both the spirit or optical levels are affected by gravity you have a
great framework for basing your GPS survey.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Most of my work has been using Thales/Magellan DSNP Dual
Frequency Long Range Kinematic GPS. They way we use this is to set up a base
station in a convenient location.(Usually a high hill/mountain) within 40km of
the job. There will be surveyors reading this saying I’m crazy, but
believe me Thales mean LONG range kinematic.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Anyway I’d observe a network of previously established bench
marks with Horizontal and vertical coordinates. That would establish my survey
reference framework. After that any new or unknown points would then be coordinated
relative to this framework.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>In your case you may not have this network of existing “control”.
This is the challenge. I have transferred control using the above technique.
What that means is as you survey points that are unknown as above they become “known”.
You can then pick up your equipment, transfer it to a convenient location
closer to job site and use then new benchmarks as control for the new site.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>This is not a job to be taken lightly. I’m also not too
sure what the terrain is like in Kalimantan but I assume difficult to traverse.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<div>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>
proj-bounces@lists.maptools.org [mailto:proj-bounces@lists.maptools.org] <b>On
Behalf Of </b>Clifford J Mugnier<br>
<b>Sent:</b> Thursday, 6 March 2008 2:50 AM<br>
<b>To:</b> PROJ.4 and general Projections Discussions<br>
<b>Subject:</b> RE: [Proj] geoid in Kalimantan, Indonesia<o:p></o:p></span></p>
</div>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<div id=idOWAReplyText99414>
<div>
<p class=MsoNormal><span style='font-size:10.0pt;color:black'>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!</span><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt'> <o:p></o:p></span></p>
</div>
<div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt'>Clifford J. Mugnier, C.P.,
C.M.S.<o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt'>LSU Student ASCE Chapter
Faculty Advisor<o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt'>and<br>
National Director (2006-2008),<br>
Photogrammetric Applications Division<br>
American Society for Photogrammetry and Remote Sensing <o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt'>and <o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt'>Chief of Geodesy,<br>
CENTER FOR GEOINFORMATICS <o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt'>Department of Civil
Engineering <o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt'>CEBA 3223A<br>
LOUISIANA STATE UNIVERSITY <o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt'>Baton Rouge, LA 70803<br>
Voice and Facsimile: (225) 578-8536 [Academic] <o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt'>Voice and Facsimile:
(225) 578-4474 [Research] <o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt'>Honorary Life Member of the <o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt'>Louisiana Society of
Professional Surveyors <o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt'>Member Emeritus of the ASPRS <o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt'>Member of the Americas
Petroleum Survey Group<br>
======================================================<br>
<a
href="https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.ls"
target="_blank">http://www.asprs.org/resources/GRIDS/</a><br>
======================================================<o:p></o:p></span></p>
</div>
</div>
</div>
<div>
<p class=MsoNormal><o:p> </o:p></p>
<div class=MsoNormal align=center style='text-align:center'>
<hr size=3 width="100%" align=center>
</div>
<p class=MsoNormal style='margin-bottom:12.0pt'><b><span style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'>From:</span></b><span style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'> 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</span><o:p></o:p></p>
</div>
<div>
<p><span style='font-size:10.0pt'>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></span><o:p></o:p></p>
</div>
</div>
</body>
</html>