HPGN Datum? (fwd)
bill at BINKO.NET
Mon Apr 25 23:43:33 EDT 2005
On Mon, 25 Apr 2005, Frank Warmerdam wrote:
> I believe that PROJ.4 +x_0 and +y_0 values are always in meters,
> while the WKT (.prj) file has the false easting and northing in the
> units of the projected coordinate systems .. feet in this case.
> In any event, if you error is on the order of 100m then the
> problem is likely not the false northing being off by 350000
> (meters or feet). That level of error is mostly likely related to
> the datum shifting not being applied or possibly a mixup between
> different kinds of feet. I am doubtful it is related to HPGN since
> my understanding is that the difference between NAD83 and HPGN
> is small (less than 5 meters say), though I am not too sure about that
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?
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.
I'd appreciate it.
SIZE 800 500
#I found these by trial and error
EXTENT 269734.497070 1356039.428711 276082.153320 1360006.713867
#the closed entry in the epsg file
SIZE 200 2
COLOR 0 0 0
OUTLINECOLOR 0 0 0
COLOR 0 0 0
OUTLINECOLOR 50 50 50
COLOR 200 0 0
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