[Liblas-devel] Re: GetProj4() string and NAD83

[Adam Stylinski]

On Thu, Dec 29, 2011 at 12:42 PM, Adam Stylinski <stylinae at mail.uc.edu>wrote:

> Hello,
>
> I'm having issues with LADAR files which do not use the WGS84 coordinate
> system.  I am translating coordinates into longitude and latitude and
> testing with google earth.  Whenever a LAS file has NAD83 coordinate it
> seems to have a tendency to be completely wrong (most of which end up being
> somewhere in the ocean).  Is there something I'm doing that doesn't work?
>
> I use the GetProj4() to get the proj4 string.  I then do a
> pj_init_plus(proj4str) to get the represented coordinate system, and then
> do a pj_latlong_from_proj() on that coordinate system to get the lat/long
> coordinate system.  Then to translate to lat/long I do a pj_transform with
> the src being the original coordinate system, the destination being the
> lat/long coordinate system, the next two parameters being 1,1, and the x
> and y being from a point pulled from GetX(), GetY().  Am I doing this
> wrong?
>

I should probably mention that I'm failing on this one (though any NAD83
coordinate seems to fail):
http://liblas.org/samples/IowaDNR-CloudPeakSoft-1.0-UTM15N.las
The GetProj4() returns this:
GetProj4() = +proj=tmerc +lat_0=0 +lon_0=0 +k=1 +x_0=0 +y_0=0 +datum=NAD83
+units=m
+geoidgrids=g2003conus.gtx,g2003alaska.gtx,g2003h01.gtx,g2003p01.gtx
+no_defs
And GetWKT():
GetWKT() = COMPD_CS["unknown",
    PROJCS["NAD83 / UTM zone 15N",
        GEOGCS["NAD83",
            DATUM["North_American_Datum_1983",
                SPHEROID["GRS 1980",6378137,298.2572221010002,
                    AUTHORITY["EPSG","7019"]],
                AUTHORITY["EPSG","6269"]],
            PRIMEM["Greenwich",0],
            UNIT["degree",0.0174532925199433],
            AUTHORITY["EPSG","4269"]],
        PROJECTION["Transverse_Mercator"],
        PARAMETER["latitude_of_origin",0],
        PARAMETER["central_meridian",0],
        PARAMETER["scale_factor",1],
        PARAMETER["false_easting",0],
        PARAMETER["false_northing",0],
        UNIT["metre",1,
            AUTHORITY["EPSG","9001"]],
        AUTHORITY["EPSG","26915"]],
    VERT_CS["NAVD88 height",
        VERT_DATUM["North American Vertical Datum 1988",2005,
            AUTHORITY["EPSG","5103"],

EXTENSION["PROJ4_GRIDS","g2003conus.gtx,g2003alaska.gtx,g2003h01.gtx,g2003p01.gtx"]],
        UNIT["metre",1,
            AUTHORITY["EPSG","9001"]],
        AXIS["Up",UP],
        AUTHORITY["EPSG","5703"]]]
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