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

[Howard Butler]

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 

note the parameters, they're all 0.

I don't know whether or not this is a bad set (or incompletely specified) of GeoTIFF keys, or whether or not GDAL should be taking the ProjectedCSTypeGeoKey straight off, as this defines the coordinate system parameters fully via lookup.  Frank, are you still around?

Howard