HPGN Datum? (fwd)

[Bill Binko]

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.

Fair enough...

>
> 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
> part.

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.

Bill

MAP
    NAME BadProj
    STATUS ON
    SIZE 800 500
    IMAGETYPE PNG
    SHAPEPATH "/var/www/binko.net/maps/data/"
    UNITS METERS
        #I found these by trial and error
        EXTENT 269734.497070 1356039.428711 276082.153320 1360006.713867
        PROJECTION
        #the closed entry in the epsg file
                "init=epsg:26759"
        END
    WEB
        TEMPLATE "/var/www/binko.net/maps/template1.html"
        IMAGEPATH "/var/www/binko.net/maps/tmp/"
        IMAGEURL "/maps/tmp/"
                LOG "/var/www/binko.net/maps/error.log"
    END
        SCALEBAR
                STATUS ON
                STYLE 1
                        INTERVALS 4
                        SIZE 200 2
                        COLOR 0 0 0
                        OUTLINECOLOR 0 0 0
                        UNITS miles
                        LABEL
                                COLOR 0 0 0
                                SIZE small
                        END
                END
        LAYER
                NAME "AllParcels"
                PROJECTION
                        "init=epsg:26759"
                END
                TYPE POLYGON
                STATUS DEFAULT
                DATA "Parcel_polygons_NAD27"
                DEBUG on
                CLASS
                        NAME "Parcels"
                        OUTLINECOLOR 50 50 50
                        SYMBOL 0
                END
        END
                LAYER
                        NAME "Roads"
                        TYPE LINE
                        STATUS DEFAULT
                        PROJECTION
                                "+proj=aea"
                                "+lat_1=24"
                                "+lat_2=31.5"
                                "+lat_0=24"
                                "+lon_0=-84"
                                "+x_0=400000"
                                "+y_0=0"
                                "+ellps=GRS80"
                                "+datum=NAD83"
                                "+units=m"
                                "+no_defs"
                        END
                        DATA "tgrr0052"
                        CLASS
                                NAME "Roads"
                                COLOR 200  0 0
                                SYMBOL 0
                        END
                END
        END