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

[Adam Stylinski]

On Tue, Jan 10, 2012 at 4:10 PM, Frank Warmerdam <warmerdam at pobox.com>wrote:

> On Tue, Jan 10, 2012 at 9:01 AM, Howard Butler <hobu.inc at gmail.com> wrote:
> >
> > On Jan 10, 2012, at 10:30 AM, Howard Butler wrote:
> >> I'll try to dig into this some more...
> >
> > GDAL isn't turning this into a proper proj.4 string.
> >
> >>      GTModelTypeGeoKey (Short,1): ModelTypeProjected
> >>       GTCitationGeoKey (Ascii,14): "UTM zone 15N"
> >>       GeogGeodeticDatumGeoKey (Short,1): Datum_North_American_Datum_1983
> >>       GeogEllipsoidGeoKey (Short,1): Ellipse_GRS_1980
> >>       ProjectedCSTypeGeoKey (Short,1): PCS_NAD83_UTM_zone_15N
> >>       ProjCoordTransGeoKey (Short,1): CT_TransverseMercator
> >>       ProjLinearUnitsGeoKey (Short,1): Linear_Meter
> >>       VerticalCSTypeGeoKey (Short,1):
> VertCS_North_American_Vertical_Datum_1988
> >>       VerticalCitationGeoKey (Ascii,19): "GEOID 2003 Applied"
> >>       VerticalUnitsGeoKey (Short,1): Linear_Meter
> >
> > is coming out of GDAL as:
> >
> >> +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
> +vunits=m +no_defs
>
> Folks,
>
> The problem is that ProjCoordTransGeoKey is seto to CT_TransverseMercator
> but there are no actual projection method parameters.  When the Geokey
> interpreter sees  ProjCoordTransGeoKey it looks for a user defined
> projected
> coordinate system and ignores the predefined one (PCS_NAD83_UTM_zone_15N).
>
> I consider this an improperly defined set of geokeys.  If
> ProjCoordTransGeoKey
> is provided then the projection method parameters should also be provided.
> Alternatively drop the ProjCoordTransGeoKey and let the system use
> the ProjectedCSTypeGeoKey.
>
> 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
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>
> Unfortunately most of the data on the internet follows this convention.
 Is there an easy workaround to this other than manually specifying
parameters?
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