<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META http-equiv=Content-Type content="text/html; charset=iso-8859-1">
<META content="MSHTML 6.00.2800.1106" name=GENERATOR>
<STYLE></STYLE>
</HEAD>
<BODY bgColor=#d8d0c8>
<DIV><FONT face=Arial size=2>Took a look at your Southampton Water problem and
the words Datum Shift immediately sprang to mind. I often have to solve these
problems of old to new datums. (I am working on a Munich based GIS problem at
the moment)</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>I have spent a long time learning this stuff and am stil not
expert at it. I warn you it is more complicated than it looks! If I had time I
might be able to help. Sadly I do not! :(</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>If you are editing OS data it is most likely to be in a very
old "topocentric" datum or tie point between the map and the earth.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>GPS data is collected with reference to the centre of the
earth or "geocentric" data.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Acouple of links for you to check this out.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2><A
href="http://soaring.aerobatics.ws/SOARING/BGA/os-note.html">http://soaring.aerobatics.ws/SOARING/BGA/os-note.html</A></FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2><A
href="http://www.gps.gov.uk/guide5.asp">http://www.gps.gov.uk/guide5.asp</A></FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2><A
href="http://www.gpsinformation.org/dale/measure.htm">http://www.gpsinformation.org/dale/measure.htm</A></FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT size=2>.....and this paper from the chap who really knows what he is
talking about....</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2><A
href="http://www.asprs.org/resources/grids/10-2003-unitedkingdom.pdf">www.asprs.org/resources/grids/10-2003-unitedkingdom.pdf</A></FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I hope this helps!</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Jeremy Stocks.</FONT></DIV></BODY></HTML>