[gdal-dev] C# OGRSpatialReference class -SetLinearUnits or SetLinearUnitsAndUpdateParameters()?

[Mark Cheyne]

Tamas - funny that you mention issue 2081 - I reported
that issue awhile back. Clearly I haven't yet upgraded
since you addressed the issue - my use of my custom
Constants class in the snippet below is my workaround
for the issue, the values are correct. 

Anyway, it is not the cause of my current problem. I
will add a ticket for you to SWIGify
SetLinearUnitsAndUpdateParameters().

Though I'm still curious what the differing purposes
of SetLinearUnits() and
SetLinearUnitsAndUpdateParameters() are, and this
might not be a fix for my actual problem anyway. I'll
look into it more.

Thank you!

--- Tamas Szekeres <szekerest at gmail.com> wrote:

> Mark,
> 
> This problem might be related to the following bug:
> http://trac.osgeo.org/gdal/ticket/2081
> 
> You should check the correctness of the actual
> constant values passed
> to SetLinearUnits();
> 
> The fix related to this issue is fairly new so you'd
> better use the
> recent FWTools if possible.
> 
> I confirm that the SetLinearUnitsAndUpdateParameters
> is not exposed to
> the SWIG API right now, so you might want to submit
> a ticket in case
> you'd like to use that.
> 
> 
> Best regards,
> 
> Tamas
> 
> 
> 
> 2008/1/17, Mark Cheyne <cheynm at yahoo.com>:
> > The class documentation for the
> OGRSpatialReference
> > class
> >
>
(http://www.gdal.org/ogr/classOGRSpatialReference.html)
> > describes two methods to set the linear units of a
> > projected coordinate system:
> >
> > * SetLinearUnits() -
> >
>
http://www.gdal.org/ogr/classOGRSpatialReference.html#2016fee7b234666c5e94d528661e6729
> >
> >
> > * SetLinearUnitsAndUpdateParameters() -
> >
>
http://www.gdal.org/ogr/classOGRSpatialReference.html#daab3d6e836f93974022bd78e221c4b4
> >
> >
> > Using C# with the binaries/wrappers that come with
> > FWTools 2.0.3, the second method does not appear
> on
> > this class.
> >
> > * Is its absence intentional or accidental?
> > * When is it appropriate to use one or the other?
> >
> > I am having trouble creating a correct NAD83HARN
> UTM
> > zone 15N PCS in units of feet.
> >
> > Look at the code below, and the Proj4 and WKT it
> > produces. I think the false easting is getting
> wonked
> > - note the Proj4 says it is 152,400.3 feet, but
> the
> > WKT says it is 500,000 meters. Seems like a meters
> > conversion is getting misapplied? Or am I using
> the
> > class incorrectly?
> >
> > OSGeo.OSR.SpatialReference sr = new
> > SpatialReference("");
> > sr.SetProjCS("NAD83(HARN) / UTM zone 15N");
> > sr.SetWellKnownGeogCS("EPSG:4152");
> > sr.SetUTM(15, 1);
> > sr.SetLinearUnits(Constants.SRS_UL_US_FOOT,
> > Constants.SRS_UL_US_FOOT_CONV);
> >
> > The Proj.4 params I get:
> >
> > +proj=tmerc +lat_0=0 +lon_0=-93 +k=0.9996
> > +x_0=152400.3 +y_0=0 +ellps=GRS80 +units=us-ft
> > +no_defs
> >
> >
> >
> > The WKT I get:
> >
> > PROJCS["NAD83(HARN) / UTM zone 15N",
> >     GEOGCS["NAD83(HARN)",
> >        
> DATUM["NAD83_High_Accuracy_Regional_Network",
> >             SPHEROID["GRS
> 1980",6378137,298.257222101,
> >
> >                 AUTHORITY["EPSG","7019"]],
> >             AUTHORITY["EPSG","6152"]],
> >         PRIMEM["Greenwich",0,
> >             AUTHORITY["EPSG","8901"]],
> >         UNIT["degree",0.01745329251994328,
> >             AUTHORITY["EPSG","9122"]],
> >         AUTHORITY["EPSG","4152"]],
> >     PROJECTION["Transverse_Mercator"],
> >     PARAMETER["latitude_of_origin",0],
> >     PARAMETER["central_meridian",-93],
> >     PARAMETER["scale_factor",0.9996],
> >     PARAMETER["false_easting",500000],
> >     PARAMETER["false_northing",0],
> >     UNIT["U.S. Foot",0.3048006]]
> >
> >
> >
> > Mark Cheyne
> > (608) 332-2235 (cell)
> >
> >
> >      
>
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> 



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