Coordinate convertion

[sereneegym]

Hello Martin..

I'm new comer for your group..Thank you for your invitation...

I'm from sri lanka and work as photogrammetry and lidar technician in survey department.

I need your help and advice..

This is i want to know..

I have las data with SLD99 coordinate system of sri lankan local coordinate system. I need convert that coordinates to WGS84.
Itz like x,y,z coordinate convert to lat.long. Coordinates.
I get .xyz file from after processing of DSM. The file of .xyz is inclute x,y,z coordinates..
Like
X= 135678. Lat = ????
Y=583945 Long = ?????
Z= 10.5. Z=10.5

Can you give some idea for that convertion. I try to do in ARC gis and qgis.but it not success....

Thank you

Serene

[Martin Isenburg]

Hello Serene,

it seems you are referring to this projection here

http://spatialreference.org/ref/sr-org/8178/html/

that uses a Transverse Mercator projection with a datum defined on the "Everest 1830" ellipsoid shown below. And from there you want to go to the WGS84 datum? Unfortunately datum transforms are not supported by LAStools. But you can go to long lat on the current datum "Everest 1830".

>> more srilanka_sld99.txt

x, y, z

135678, 583945, 10.5

135688, 583945, 10.5

135688, 583955, 10.5

135678, 583955, 10.5

>> las2las -i srilanka_sld99.txt ^

                 -epsg 5235 ^

                 -target_longlat ^

                 -o srilanka_longlat.laz

using target projection 'longitude/latitude'

WARNING: cannot parse 'x, y, z' with 'xyz'. skipping ...

GeographicTypeGeoKey: look-up for ellipsoid with id 7 not implemented

>> las2txt -i srilanka_longlat.laz -stdout

77.4700843 7.7468302 10.50

77.4701748 7.7468309 10.50

77.4701741 7.7469212 10.50

77.4700836 7.7469205 10.50

>> lasboundary -i srilanka_longlat.laz -okml -labels

Interesting to see how far we are off. Can this be due to the different datum??? Or did I pick the wrong EPSG code? Either way, LAStools is not able to do these more rare conversion. But have a look at the 'las2las' from libLAS or PDAL.

Regards,

Martin @rapidlasso

PROJCS["SLD99 / Sri Lanka Grid 1999",
    GEOGCS["SLD99",
        DATUM["Sri Lanka Datum 1999",
            SPHEROID["Everest 1830 (1937 Adjustment)",6377276.345,300.8017,
                AUTHORITY["EPSG","7015"]],
            AUTHORITY["EPSG","1053"]],
        PRIMEM["Greenwich",0,
            AUTHORITY["EPSG","8901"]],
        UNIT["degree",3.14159265358979,
            AUTHORITY["EPSG","9001"]],
        AUTHORITY["EPSG","5233"]],
    UNIT["metre",1,
        AUTHORITY["EPSG","9001"]],
    PROJECTION["Transverse Mercator"],
    PARAMETER["Latitude of natural origin",7.00016975],
    PARAMETER["Longitude of natural origin",80.46181671],
    PARAMETER["Scale factor at natural origin",0.9999238418],
    PARAMETER["False easting",500000],
    PARAMETER["False northing",500000],
    AUTHORITY["EPSG","5235"],
    AXIS["Easting",east],
    AXIS["Northing",north]]

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