[gdal-dev] SRS-Transformation(DHDN/GK=>ETRS89/UTM) with towgs84 -
Accuracy
Gregor Fikoczek
gregor.fikoczek at wheregroup.com
Wed Mar 4 09:53:29 EST 2009
Hi list,
i figured out why the accuracy was so bad using the towgs84-Option:
the scaling was not in parts per million indicated
wrong scaling-specification:
---------------------------------------------
=> 1.00001651559
ogr2ogr -s_srs "+proj=tmerc +lat_0=0 +lon_0=6 +x_0=2500000 +y_0=0
+ellps=bessel +units=m
+towgs84=590.1181,99.6226,340.1890,1.185095,-1.334952,-2.904521,1.00001651559" -t_srs "+proj=utm
+ellps=GRS80 +datum=WGS84 +zone=32" -f GML points_7P_gdal.gml points.gml
right scaling-specification:
---------------------------------------------
=> 16.51559 (ppm)
ogr2ogr -s_srs "+proj=tmerc +lat_0=0 +lon_0=6 +x_0=2500000 +y_0=0
+ellps=bessel +units=m
+towgs84=590.1181,99.6226,340.1890,1.185095,-1.334952,-2.904521,16.51559" -t_srs "+proj=utm
+ellps=GRS80 +datum=WGS84 +zone=32" -f GML points_7P_gdal.gml points.gml
-----------------------------------------------------------------------------------------------------------
Results | difference
East[m] | North[m] | E | N | distance
-----------------------------------------------------------------------------------------------------------
340408,046 5617072,499 -0,013 -0,012 0,018
342695,227 5614819,736 0,003 0,013 0,013
343584,887 5608927,612 0,014 0,026 0,030
=========
Accuracy:
=========
~ 0.3 m
Best Regards,
Greg
>---------- Weitergeleitete Nachricht ----------
>
>Betreff: SRS-Transformation(DHDN/GK=>ETRS89/UTM) with towgs84 - Accuracy
>Datum: Mittwoch 04 März 2009
>Von: Gregor Fikoczek <gregor.fikoczek at wheregroup.com>
>An: gdal-dev at lists.osgeo.org
>
>
>Hi list,
>
>i am trying to transform some point (in a gml-file) from DHDN/GK3 - srs to
>ETRS89/UTM - srs in some diferent ways:
>
>
>some points(gml-File) in start-srs
>-----------------------------------------------------------------------------------------------------------
>Pointnr. | X[m] | Y[m]
>-----------------------------------------------------------------------------------------------------------
>5216100002 | 2552401,862 | 5616707,524
>5414100047 | 2554778,697 | 5614549,001
>5508100055 | 2555906,314 | 5608696,986
>
>some points(gml-File) in target-srs
>-----------------------------------------------------------------------------------------------------------
>Punktnr. | East[m] | North[m]
>-----------------------------------------------------------------------------------------------------------
>5216100002 32340408,033 5617072,487
>5414100047 32342695,230 5614819,749
>5508100055 32343584,901 5608927,638
>
>
>1.) using the srs defined in the proj-epsg-File:
>
>ogr2ogr -s_srs EPSG:31466 -t_srs EPSG:25832 -f GML points_etrs_gdal.gml
>points.gml
>
>-----------------------------------------------------------------------------------------------------------
>Results | difference
>East[m] | North[m] | E | N | distance
>-----------------------------------------------------------------------------------------------------------
>340411,269 | 5617068,431 | -3,236 | 4,056 | 5,188
>342698,445 | 5614815,708 | -3,215 | 4,041 | 5,164
>343588,142 | 5608923,646 | -3,241 | 3,992 | 5,142
>
>
>2.) using a nadgrid (BETA 2007)
>
>ogr2ogr -s_srs "+proj=tmerc +lat_0=0 +lon_0=6 +k=1.000000 +x_0=2500000 +y_0=0
>+ellps=bessel +units=m +nadgrids=./BETA2007.gsb +wktext" -t_srs "+proj=utm
>+ellps=GRS80 +datum=WGS84 +zone=32" -f GML points_BETA2007_gdal.gml
>points.gml
>
>-----------------------------------------------------------------------------------------------------------
>Results | difference
>East[m] | North[m] | E | N | distance
>-----------------------------------------------------------------------------------------------------------
>340408,064 | 5617072,481 | -0,031 | 0,006 | 0,031
>342695,246 | 5614819,723 | -0,016 | 0,026 | 0,031
>343584,918 | 5608927,610 | -0,017 | 0,028 | 0,033
>
>3.) using towgs-option (Transform-Parameter)
>
>ogr2ogr -s_srs "+proj=tmerc +lat_0=0 +lon_0=6 +x_0=2500000 +y_0=0
>+ellps=bessel +units=m
>+towgs84=590.1181,99.6226,340.1890,1.185095,-1.334952,-2.904521,1.00001651559" -t_srs "+proj=utm
>+ellps=GRS80 +datum=WGS84 +zone=32" -f GML points_7P_gdal.gml points.gml
>
>-----------------------------------------------------------------------------------------------------------
>Results | difference
>East[m] | North[m] | E | N | distance
>-----------------------------------------------------------------------------------------------------------
>340408,056 | 5617072,821 | -0,023 | -0,334 | 0,334
>342695,237 | 5614820,058 | -0,007 | -0,309 | 0,309
>343584,897 | 5608927,933 | 0,004 | -0,295 | 0,295
>
>
>Parameter:
>dX +590.1181m
>dY +99.6226 m
>dZ +340.1890 m
>rX +1.185095"
>rY -1.334952"
>rZ -2.904521"
>dm = 1.00001651559
>
>
>=========
>Accuracy:
>=========
>1.) ~ 5m
>2.) ~ 0.033 m
>3.) ~ 0.3 m <=== Why so bad ???
>
>The accurancy by using the towgs-option is worse then expected, i was
>expecting ~ 0.02 m. Aspacielly the difference in North
>(-0,334, -0,309, -0,295) is remarkable.
>
>So maybe an algebraic sign is incorrect or what ever, anybody a suggestion?
>
>Best regards,
>Greg
>
---------------------------------------
WhereGroup GmbH & Co. KG
Siemensstraße 8
53121 Bonn
Germany
Gregor Fikoczek
Email: gregor.fikoczek at wheregroup.com
Fon: +49 (0)228 / 90 90 38 - 25
Fax: +49 (0)228 / 90 90 38 - 11
info at wheregroup.com
www.wheregroup.com
Amtsgericht Bonn, HRA 6788
-------------------------------
Komplementärin:
WhereGroup Verwaltungs GmbH
vertreten durch:
Olaf Knopp, Peter Stamm
---------------------------------------
-------------------------------------------------------
--
Mit freundlichen Grüßen / Kind regards
Gregor Fikoczek
---------------------------------------
WhereGroup GmbH & Co. KG
Siemensstraße 8
53121 Bonn
Germany
Gregor Fikoczek
Email: gregor.fikoczek at wheregroup.com
Fon: +49 (0)228 / 90 90 38 - 25
Fax: +49 (0)228 / 90 90 38 - 11
info at wheregroup.com
www.wheregroup.com
Amtsgericht Bonn, HRA 6788
-------------------------------
Komplementärin:
WhereGroup Verwaltungs GmbH
vertreten durch:
Olaf Knopp, Peter Stamm
---------------------------------------
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