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<DIV dir=ltr align=left><SPAN class=262514013-06102008><FONT face=Arial>Thanks
for explaining. I did not understand that the extra False
Northing should be added only south of the False
Origin. </FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=262514013-06102008><FONT face=Arial>Let me
see if I got it right.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=262514013-06102008><FONT
face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=262514013-06102008><FONT
face=Arial>So, in the Lambert Sud Algerie Grid, there is one False
Northing that is 300 km, and an extra False Northing that is 1000 km?
</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=262514013-06102008><FONT face=Arial>As one
goes south from the northmost part of the map grid, the Northing value would
decrease </FONT></SPAN><SPAN class=262514013-06102008><FONT face=Arial>until it
reaches 300 km at the Origin, </FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=262514013-06102008><FONT face=Arial>but
there the Northing would wrap around and become 1300 km? </FONT></SPAN><SPAN
class=262514013-06102008><FONT face=Arial>And then it would decrease again, if
one would go further south. </FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=262514013-06102008><FONT
face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=262514013-06102008><FONT
face=Arial>Tricky. Reminds me of UTM. I can see that it works on a
paper map, but I suppose most GIS systems would have </FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=262514013-06102008><FONT face=Arial>to
implement such a map grid as two separate projections.
</FONT></SPAN></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><SPAN class=262514013-06102008><FONT
face=Arial>Regards,</FONT></SPAN></DIV><!-- Converted from text/plain format -->
<P><FONT size=2>--<BR>Mikael Rittri<BR>Carmenta AB<BR>Box 11354<BR>SE-404 28
Göteborg<BR>Visitors: Sankt Eriksgatan 5<BR>SWEDEN<BR>Tel: +46-31-775 57
37<BR>Mob: +46-703-60 34
07<BR>mikael.rittri@carmenta.com<BR>www.carmenta.com</FONT> <BR></P>
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<HR tabIndex=-1>
<FONT face=Tahoma size=2><B>From:</B> Clifford J Mugnier [mailto:cjmce@lsu.edu]
<BR><B>Sent:</B> den 6 oktober 2008 15:33<BR><B>To:</B> PROJ.4 and general
Projections Discussions<BR><B>Cc:</B> Mikael Rittri<BR><B>Subject:</B> RE:
[Proj] Terminology for origins<BR></FONT><BR></DIV>
<DIV></DIV>
<DIV id=idOWAReplyText38958 dir=ltr>
<DIV dir=ltr><FONT face="Times New Roman" size=2>Sorry you find it
contradictory, but it remains a fact. When you get to zero and still need
to go further south to use the same grid system, they add an additional number
to that zero for a significant "jump." I have not ever seen it used for
False Easting; just for False Northing. </FONT></DIV>
<DIV dir=ltr><FONT face="Times New Roman" size=2></FONT> </DIV>
<DIV dir=ltr><FONT face="Times New Roman" size=2>The French Lambert Sud Algerie
Grid has a False Northing of 300 km at the origin of 33<SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA">º<SPAN
style="mso-spacerun: yes"> 18</SPAN>' North. <STRONG>("South of
the False Origin add 1,000,000 meters to the northings").</STRONG>
The original grid tables are <EM>Tables de Projeciton Systeme Lambert Nort
Maroc.</EM><SPAN style="mso-spacerun: yes"> The EPSG has an interesting
database for such things, however I consider my personal holdings
as authoritative in most cases that differ. This is one of
those common cases. </SPAN></SPAN></FONT></DIV>
<DIV dir=ltr><FONT face="Times New Roman" size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA"><SPAN
style="mso-spacerun: yes"></SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr><FONT face="Times New Roman" size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA"><SPAN
style="mso-spacerun: yes">Regards,</SPAN></SPAN></FONT></DIV>
<DIV dir=ltr><FONT face="Times New Roman" size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA"><SPAN
style="mso-spacerun: yes"></SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr><FONT face="Times New Roman" color=#000000 size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA"><SPAN
style="mso-spacerun: yes"><SPAN style="FONT-SIZE: 10pt">Clifford J. Mugnier,
C.P., C.M.S.<BR>Past National Director (2006-2008),<BR>Photogrammetric
Applications Division<BR>American Society for Photogrammetry and Remote Sensing
<BR>and <BR>Chief of Geodesy,<BR>CENTER FOR GEOINFORMATICS <BR>Department of
Civil Engineering <BR>Patrick F. Taylor Hall 3223A<BR>LOUISIANA STATE UNIVERSITY
<BR>Baton Rouge, LA 70803<BR>Voice and Facsimile: (225) 578-8536
[Academic] <BR>Voice and Facsimile: (225) 578-4474 [Research] <BR>Honorary
Life Member of the <BR>Louisiana Society of Professional Surveyors <BR>Member
Emeritus of the ASPRS <BR>Member of the Americas Petroleum Survey
Group<BR>======================================================<BR></SPAN><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><FONT
size=2><SPAN
style="FONT-SIZE: 10pt">http://www.asprs.org/resources/GRIDS/</SPAN></FONT></A><BR><FONT
size=2><SPAN
style="FONT-SIZE: 10pt">======================================================</SPAN></FONT></SPAN></SPAN></FONT></DIV></DIV>
<DIV dir=ltr><BR>
<HR tabIndex=-1>
<FONT face=Tahoma size=2><B>From:</B> proj-bounces@lists.maptools.org on behalf
of Mikael Rittri<BR><B>Sent:</B> Mon 06-Oct-08 02:03<BR><B>To:</B> PROJ.4 and
general Projections Discussions<BR><B>Subject:</B> RE: [Proj] Terminology for
origins<BR></FONT><BR></DIV>
<DIV dir=ltr>
<DIV dir=ltr align=left><FONT face=Arial>Clifford J Mugnier<SPAN
class=259515106-06102008> wrote ( <SPAN class=259515106-06102008><A
href="http://lists.maptools.org/pipermail/proj/2008-October/003865.html">http://lists.maptools.org/pipermail/proj/2008-October/003865.html</A> ):</SPAN></SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Tahoma><FONT size=2><SPAN
class=259515106-06102008><FONT face=Arial
size=3></FONT></SPAN></FONT></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Tahoma><FONT size=2><SPAN
class=259515106-06102008><FONT face=Arial size=3>> In North
Africa, several of the Grids also have a False Northing at the False Origin
in order to avoid negative northings.</FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial><FONT size=3><SPAN
class=259515106-06102008>> </SPAN>Really!</FONT></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial><FONT size=3><SPAN
class=259515106-06102008>> </SPAN>:-)<SPAN
class=259515106-06102008> </SPAN></FONT></FONT></DIV>
<DIV dir=ltr align=left><SPAN class=259515106-06102008><FONT face=Arial
size=3></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=259515106-06102008><FONT face=Arial
size=3>Sorry, I don't understand. In what sense are you using the term
"False Origin" here? </FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=259515106-06102008><FONT face=Arial
size=3></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=259515106-06102008><FONT face=Arial
size=3>If you are using it as EPSG does (at least for Lambert Conformal Conic
2SP </FONT></SPAN></DIV>
<DIV dir=ltr align=left><FONT face=Arial><FONT size=3><SPAN
class=259515106-06102008><FONT size=+0>and Polar Stereographic Variant C),
</FONT></SPAN><SPAN class=259515106-06102008><FONT size=+0>then your statement
is not surprising, since </FONT></SPAN></FONT></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial><FONT size=3><SPAN
class=259515106-06102008><FONT size=+0>that's how </FONT></SPAN><SPAN
class=259515106-06102008>such a False Origin works: it does have a False
Northing and a </SPAN></FONT></FONT></DIV>
<DIV dir=ltr align=left><SPAN class=259515106-06102008><FONT size=3>False
Easting. </FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=259515106-06102008><FONT face=Arial
size=3></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=259515106-06102008><FONT face=Arial
size=3>If you are using it in the other sense, as the point where False Easting
and False Northing</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=259515106-06102008><FONT face=Arial
size=3>are both zero, then your statement is contradictory (that's a little too
surprising). </FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=259515106-06102008><FONT face=Arial
size=3></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=259515106-06102008><FONT face=Arial
size=3>So, you must be using the term "False Origin" in some third, more general
way. </FONT></SPAN></DIV>
<DIV dir=ltr align=left><FONT face=Arial><FONT size=3><SPAN
class=259515106-06102008><FONT size=+0>Could you give a concrete
</FONT></SPAN><SPAN class=259515106-06102008>numerical example?
</SPAN></FONT></FONT></DIV>
<DIV dir=ltr align=left><SPAN class=259515106-06102008><FONT face=Arial
size=3></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=259515106-06102008><FONT face=Arial
size=3>Best regards,</FONT></SPAN></DIV>
<DIV dir=ltr align=left></SPAN></FONT></FONT><FONT size=2></FONT> </DIV>
<DIV dir=ltr align=left><FONT size=2>--<BR>Mikael Rittri<BR>Carmenta AB<BR>Box
11354<BR>SE-404 28 Göteborg<BR>Visitors: Sankt Eriksgatan 5<BR>SWEDEN<BR>Tel:
+46-31-775 57 37<BR>Mob: +46-703-60 34
07<BR>mikael.rittri@carmenta.com<BR>www.carmenta.com</FONT>
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