HPGN Datum? (fwd)

[Frank Warmerdam]

On 4/25/05, Bill Binko <bill at binko.net> wrote:
> Ok, well, I'm putting a stripped down version of my mapfile below.  It has
> only two layers: one in each of the two projections.  I tried replacing
> the "init=espg:27659" with the actual contents of my /usr/share/proj/espg
> in both the MAP level and the LAYER level, but it came back very messed
> up!  So I thought that perhaps I'm going at this wrong: I created these
> mapfiles before I had any clue and haven't come back to them in a while.
> Would you guys mind checking my setup on these?

Bill, 

Your declarations look fine from what I know of your problem (I hadn't
been following the discussion closely).   But my guess is that
the Roads layer is just not being converted back to NAD27 properly.

Do you have the file /usr/local/share/proj/conus on your system? 

One way of testing would be to change the roads declaration to be
NAD27 and see if that makes any difference.  If there is no noticable
effect, then it likely means that the datum shift file is not being found
and applied. 
                         PROJECTION
                               "+proj=aea"
                               "+lat_1=24"
                               "+lat_2=31.5"
                               "+lat_0=24"
                               "+lon_0=-84"
                               "+x_0=400000"
                               "+y_0=0"
                               "+datum=NAD27"
                               "+units=m"
                               "+no_defs"
                       END

> I'd send the data, but it's 49MB, and I'm not sure how to extract a subset
> without messing it up and/or removing the problem.

If you still can't get things working, bundle stuff up and let me know 
where to grab it and I'll take a crack at the problem. 

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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and watch the world go round - Rush    | Geospatial Programmer for Rent