simple tool for conversion

[Eric Bridger]

On Thu, 2004-12-09 at 12:12, Joseph Norris wrote:
> Ethan,
>
> At the risk of being flamed into non-existence on this subject.  I have
> repeatedly modified my map file to include the projection blocks that you
> and others in this list have mentioned.  Each change has provided no
> results.  I have sent copies of my projection file for the California zip
> map and I have received no explanation of what the terms mean. I have tried
> to get simple features to work and this has been unsuccessful.

Joseph,

We've all been there. But it take patience and the willingness to start
all over from scratch.

It has finally occured to me that the root of your problem is that your
California zip code file (is that a shape file?) is in a strange
projection.  An LCC projection but in US Feet. Meters are the usual
units used.  Early on we found this in the Proj4 epsg file with an epsg
code between 26941 and 26946.Any of these should work except for the
fact that your zip file is using US Feet vs. Meters.

E.g.
# NAD83 / California zone 1
<26941> +proj=lcc +lat_1=41.666666667 +lat_2=40.000000000
+lat_0=39.333333333 +lon_0=-122.000000000 +x_0=2000000.000
+y_0=500000.000 +ellps=GRS80 +datum=NAD83 +units=m  no_defs <>

Perhaps you could use a projection of init=epsg:26943 but with UNITS set
to FEET. Have you tried that in your map file?

That failing I would reccommend starting with a California Zip Code
shape file in lat/long coordinates.  These are available for free from
the Census bureau:

http://www.census.gov/geo/www/cob/z52000.html#shp

Hope this finally helps.

Eric