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<DIV><FONT face=Arial size=2>As I've looked closer at some of the metadata that
is available on the downloads I have, I've noticed that they sometimes say they
are a geographic projection, and use datum like NAD83... so that tells me a
little bit. However I had the mistaken idea before that NAD83 was a
"projection". I really am confused about the difference between the
data set and the projection. I thought that NAD83 was a set of data
that used a particular projection.... but then I noticed in at least one
case the metadata showed a "geographic projection", a horizantal datum, and a
vertical datum.... so I'm a bit confused.
</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>So Assuming that all my shapefiles are Geo
Lat/Long projections with NAD83 datum, how do I make them look right when they
are drawn with mapserver/mapscript? </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Thanks again,</FONT></DIV>
<DIV><FONT face=Arial size=2>Jeff</FONT></DIV>
<DIV> </DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=ed@TOPOZONE.COM href="mailto:ed@TOPOZONE.COM">Ed McNierney</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=MAPSERVER-USERS@LISTS.UMN.EDU
href="mailto:MAPSERVER-USERS@LISTS.UMN.EDU">MAPSERVER-USERS@LISTS.UMN.EDU</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Friday, January 21, 2005 11:23
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [UMN_MAPSERVER-USERS]
projection questions</DIV>
<DIV><BR></DIV>
<DIV class=Section1>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Jeff
–<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Unfortunately, ESRI
forgot about projections when the shapefile format was created. There
was a later addition of a .prj file to go along with shapefiles and describe
their projection. If you have a .prj file of the same base name, you
will have that information – I expect you do not.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Without that
information you’re down to educated guesses. There are three likely
candidates for US data – geographic (unprojected) coordinates, a UTM
projection, or a state plane projection. If you are dealing with a
multiple-state area, state plane is unlikely.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Can you examine the
coordinates in the shapefile by either using the shpdump utility or loading
the shapefile into a GIS viewer and reading the coordinates? For
<st1:place w:st="on">New England</st1:place>, geographic coordinates will have
X values ranging from around -74 to -66, and Y values between 41 and
48. UTM coordinates will range between X values of 200000 to 700000 and
Y values between 4500000 and 5250000. As you can see, these are
obviously different and easy to distinguish.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">If you find you have
values that don’t match either of these, let us know what they are; the
shpdump utility will give you the bounding box of all shapes in the shapefile,
and that’s a good guide.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal
style="MARGIN-LEFT: 33pt; TEXT-INDENT: -0.25in; mso-list: l0 level1 lfo1"><![if !supportLists]><FONT
face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><SPAN
style="mso-list: Ignore">-<FONT face="Times New Roman" size=1><SPAN
style="FONT: 7pt 'Times New Roman'">
</SPAN></FONT></SPAN></SPAN></FONT><![endif]><FONT face=Arial color=navy
size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Ed<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Ed
McNierney<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">TopoZone.com<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<DIV>
<DIV class=MsoNormal style="TEXT-ALIGN: center" align=center><FONT
face="Times New Roman" size=3><SPAN style="FONT-SIZE: 12pt">
<HR tabIndex=-1 align=center width="100%" SIZE=2>
</SPAN></FONT></DIV>
<P class=MsoNormal><B><FONT face=Tahoma size=2><SPAN
style="FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Tahoma">From:</SPAN></FONT></B><FONT
face=Tahoma size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Tahoma"> UMN
MapServer Users List [mailto:MAPSERVER-USERS@LISTS.UMN.EDU] <B><SPAN
style="FONT-WEIGHT: bold">On Behalf Of </SPAN></B>Jeff Portwine<BR><B><SPAN
style="FONT-WEIGHT: bold">Sent:</SPAN></B> Friday, January 21, 2005 10:49
AM<BR><B><SPAN style="FONT-WEIGHT: bold">To:</SPAN></B>
MAPSERVER-USERS@LISTS.UMN.EDU<BR><B><SPAN
style="FONT-WEIGHT: bold">Subject:</SPAN></B> [UMN_MAPSERVER-USERS] projection
questions</SPAN></FONT><o:p></o:p></P></DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"><o:p> </o:p></SPAN></FONT></P>
<DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"> <o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Is there an easy way to figure out
what projection my shapefile was created with? I have a map of the
<st1:place w:st="on">New England</st1:place> area that was created in
Microsoft's Map Point, and I am more or less trying to re-create that map with
mapserver. I started with an outline of the United States and
then set the extents to display the area that I wanted, but the maps look very
different and i'm positive it's becuase I'm not using proper projections
(I don't expect the maps to look exactly alike of course, but the general
shape should be pretty close). I always use ogrinfo to get
the extents and see projection information of shapefiles that I've downloaded
but more often than not , the ogrinfo just returns: "Layer SRS WKT:
(Unknown)" instead of telling me the projection it was created
with.</SPAN></FONT><o:p></o:p></P></DIV>
<DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"> <o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">I also am not sure how to go about
choosing my output projection... I've been using EPSG:4269 because as I
understand it that is a midwest projection and when I first started playing
with mapserver I was making maps of <st1:State w:st="on"><st1:place
w:st="on">Michigan</st1:place></st1:State>. Anybody know a
good source to look up what would be the best output projection for different
areas of the country/world? </SPAN></FONT><o:p></o:p></P></DIV>
<DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"> <o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">As you can tell i'm really new to
GIS and while I do understand the idea of projections I just don't know
anything about them or how to apply them.</SPAN></FONT><o:p></o:p></P></DIV>
<DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"> <o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Thanks a
lot,</SPAN></FONT><o:p></o:p></P></DIV>
<DIV>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Jeff</SPAN></FONT><o:p></o:p></P></DIV>
<DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"> <o:p></o:p></SPAN></FONT></P></DIV></DIV></BLOCKQUOTE></BODY></HTML>