[Fwd: Re: [UMN_MAPSERVER-USERS] Questions]

[Stephen Woodbridge]

Please send follow up questions back to the list. There are lots of
people that have lots of info and are willing to help. I probably don't
know the answer to all questions and others might want to hear the
answers also.

-------- Original Message --------
Subject: Re: [UMN_MAPSERVER-USERS] Questions
Date: Thu, 6 Jan 2005 09:54:29 -0500
From: Jeff Portwine <jdport at veritime.com>
To: Stephen Woodbridge <woodbri at swoodbridge.com>
References: <41DC3CF1.30104 at swoodbridge.com>
<931f8ea9050105121923378c74 at mail.gmail.com>
<000a01c4f36c$e145c4c0$5ff2fbd0 at solo> <41DC6103.6020500 at swoodbridge.com>

Thanks for answering my questions, I was wondering if you could help me
with
one more thing.
I'm trying to determine the proper projection and extents to use for my map
of Michigan.
Using ogrinfo,  I get the following on my state shape data:

>ogrinfo -al -so states.shp

INFO: Open of `states.shp'
using driver `ESRI Shapefile' successful.

Layer name: states
Geometry: Polygon
Feature Count: 1
Extent: (-90.418136, 41.696089) - (-82.418602, 48.262631)
Layer SRS WKT:
(unknown)
STFIPS: String (2.0)
STATE: String (66.0)
STPOSTAL: String (2.0)
VERSION: String (2.0)
REVISION: String (2.0)

This gave me the extents in I assume long/lat values, but doesn't give me
any information on the projection it uses.... so I tried the same thing on
the shapefile for the roads data and got:

>ogrinfo -al -so mirds.shp
Had to open data source read-only.
INFO: Open of `mirds.shp'
using driver `ESRI Shapefile' successful.

Layer name: mirds
Geometry: Line String
Feature Count: 14687
Extent: (-90.414464, 41.698072) - (-82.423253, 47.479491)
Layer SRS WKT:
GEOGCS["GCS_North_American_1983",
    DATUM["North_American_Datum_1983",
        SPHEROID["GRS_1980",6378137,298.257222101]],
    PRIMEM["Greenwich",0],
    UNIT["Degree",0.0174532925199433]]
LENGTH: Real (18.4)
HWYNAME: String (40.0)
FCC: String (3.0)
STATEFIPS: String (2.0)
ALT1_NAME: String (40.0)

I consulted this list if EPSG codes at
http://www.inovagis.org/giserver/tutorial/epsg.htm
and guessed that "North_American_Datum_1983"  was what this list showed as
NAD83, or epsg: 4269.    So, I went into my mapfile and I set the output
projection and all of my layer projections to  "init=epsg:4269" and set my
extents to  what were shown in the output of the shapefiles.       I can
see
that this wasn't right, because my map comes up blank but I'm missing
something that will help me understand how to properly determine the right
settings.

If you have a moment to spare I'd really appreciate it if you could help me
understand this.

Thanks a lot,
Jeff