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

[Adam Stylinski]

On Wed, Jan 11, 2012 at 3:03 PM, Frank Warmerdam <warmerdam at pobox.com>wrote:

> On Wed, Jan 11, 2012 at 11:44 AM, Adam Stylinski <stylinae at mail.uc.edu>
> wrote:
> > Like I mentioned in previous posts, other NAD83 geotagged las files
> produce
> > similar issues (for example fayetteville).
>
> Adam,
>
> Where are these coming from?  What are they generated with?
>
> You referred to "most of the data on the internet".  What sort of
> sampling have you done?
>
> If the problem is very limited then I think it is better to fix
> the producer or work around the issue.  If it is truely widespread
> then we might as well buckle under and make our consumer
> more robust.
>
> Best regards,
> --
>
> ---------------------------------------+--------------------------------------
> I set the clouds in motion - turn up   | Frank Warmerdam,
> warmerdam at pobox.com
> light and sound - activate the windows | http://pobox.com/~warmerdam
> and watch the world go round - Rush    | Geospatial Software Developer
>
> Here is the one I was referring to:
http://data.capcog.org/Information_Clearinghouse/data/LiDAR/Sample_LiDAR_LAS_File.zip
Many of the listed examples from lastool's compilation of ladar examples
that use NAD83 have a different issue (not particular this one).  This is
all I can find that is freely available, anyway.  The proprietary data that
we have and I'm currently working with uses WGS84, so I cannot speak for
other sources of data other than that which is available freely on the
internet.

Here is what getProj4() and getWKT() return for these datasets:

GetProj4() = +proj=lcc +lat_1=28.38333333333333 +lat_2=30.28333333333334
+lat
27.83333333333333 +lon_0=-99 +x_0=1968500 +y_0=13123333.33333333
+datum=NAD83
nits=us-ft +no_defs
GetWKT() = COMPD_CS["unknown",
    PROJCS["unnamed",
        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["Lambert_Conformal_Conic_2SP"],
        PARAMETER["standard_parallel_1",28.38333333333333],
        PARAMETER["standard_parallel_2",30.28333333333334],
        PARAMETER["latitude_of_origin",27.83333333333333],
        PARAMETER["central_meridian",-99],
        PARAMETER["false_easting",6458320.416666665],
        PARAMETER["false_northing",43055469.44444443],
        UNIT["US survey foot",0.3048006096012192,
            AUTHORITY["EPSG","9003"]],
        AUTHORITY["EPSG","32140"]],
    VERT_CS["NAVD88 - Geoid03 (Feet)",
        VERT_DATUM["unknown",2005],
        UNIT[,1,
            AUTHORITY["EPSG","9003"]],
        AXIS["Up",UP]]]

When I try to perform these projections with proj4, it gives me coordinates
somewhere in the middle of the pacific.  So no, the default parameters are
not zero, but something is making the proj.4 library behave incorrectly.  I
apologize for assuming it was the same issue just because it was the same
coordinate system.  Still, there is a problem, and your help on why this is
happening would be appreciated.
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