On 11-04-29 08:35 AM, Edwards, David wrote:
I am trying to use libLAS to read an LAS file and perform a coordinate
transformation. Points in the file are stored in UTM coordinates. I would
like to transform them into geocentric coordinates. As best I can tell, the
version of libLAS I am using (1.6.1) does not support conversion to
geocentric coordinates, so my backup plan is to convert to WGS84 geodetic
coordinates (lat., long. , height above ellipsoid), and then perform the
geodetic-to-geocentric conversion myself.
The problem is that when I set up a ReprojectionTransform to convert the
points from UTM to geodetic coordinates, the resulting latitude and
longitude of each point has nonzero digits only to the hundredth of a
degree, even though the UTM coordinates of my input points have data to the
millimeter. For example, here are the results of two such conversions:
UTM (Easting, Northing) ---> Geodetic (Longitude, Latitude) 831805.86
4296378.26 ---> -77.18 38.75 831806.31 4296377.64 ---> -77.18 38.75
Even though the points have different UTM easting and northing coordinates,
they are transformed to the same latitude and longitude. Is this limited
precision inherent in the way libLAS does its coordinate conversions, or am
I setting up the transform object(s) incorrectly?
I apologize if this is a duplicate post. I tried to send this yesterday
before joining the mailing list.
Dave,
Reprojection is generally accurate to a small fraction of a millimeter.
I believe the problem you are encountering is how you are formatting the
coordinates for reporting - not the nature of the reprojection itself.
Best regards,
--
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I set the clouds in motion - turn up | Frank Warmerdam, [email protected]
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush | Geospatial Programmer for Rent
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