Hello,
My name is Marcin and this is my first post here, so if I ma somewhere
unclear - please just let me know
I have a problem with transforming geometries from one coordinate system to
another.
Here is a description of my application.
1. I have a map that uses openstreetmap as a base map in Pseudo Mercator
coordinate system (EPSG:3857). The map client uses OpenLayers3 to draw maps.
2. I have two different data sources: shapefiles and postgis.
3. Layers in the sources have coordinate systems different than on the map.
That is why I transform the data on the fly, from their native systems to
EPSG:3857, before I send them back to the application client side.
4. Data in shapefiles uses the following coordsys definition:
PROJCS["ETRS_1989_UWPP_2000_PAS_6",
GEOGCS["GCS_ETRS_1989",
DATUM["D_ETRS_1989",
SPHEROID["GRS_1980", 6378137.0, 298.257222101]],
PRIMEM["Greenwich", 0.0],
UNIT["degree", 0.017453292519943295],
AXIS["Longitude", EAST],
AXIS["Latitude", NORTH]],
PROJECTION["Transverse_Mercator"],
PARAMETER["central_meridian", 18.0],
PARAMETER["latitude_of_origin", 0.0],
PARAMETER["scale_factor", 0.999923],
PARAMETER["false_easting", 6500000.0],
PARAMETER["false_northing", 0.0],
UNIT["m", 1.0],
AXIS["x", EAST],
AXIS["y", NORTH]]
5. The shapefiles were later imported to postgis using their import tool.
During the import I had to specify the EPSG code for the coordinate system I
showed above.
According to what I read in the net, the EPSG code for the system is 2177 -
so I used this as SRID.
6. The imported data showed that it uses the following CRS definition:
PROJCS["ETRS89 / Poland CS2000 zone 6",
GEOGCS["ETRS89",
DATUM["European Terrestrial Reference System 1989",
SPHEROID["GRS 1980", 6378137.0, 298.257222101,
AUTHORITY["EPSG","7019"]],
TOWGS84[0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0],
AUTHORITY["EPSG","6258"]],
PRIMEM["Greenwich", 0.0, AUTHORITY["EPSG","8901"]],
UNIT["degree", 0.017453292519943295],
AXIS["Geodetic latitude", NORTH],
AXIS["Geodetic longitude", EAST],
AUTHORITY["EPSG","4258"]],
PROJECTION["Transverse_Mercator", AUTHORITY["EPSG","9807"]],
PARAMETER["central_meridian", 18.0],
PARAMETER["latitude_of_origin", 0.0],
PARAMETER["scale_factor", 0.999923],
PARAMETER["false_easting", 6500000.0],
PARAMETER["false_northing", 0.0],
UNIT["m", 1.0],
AXIS["Northing", NORTH],
AXIS["Easting", EAST],
AUTHORITY["EPSG","2177"]]
This definition is in most points identical to the previous one with the
exception of names and some parts called: AUTHORITY. But its name suggest
that the system in postgis is the right one to use.
7. The problem is: the data stored in shapefile displayed in the correct
position, and data from postgis - somewhere else.
8. In my application I do the transformation using geotools 11.1 with the
following piece of code:
CoordinateReferenceSystem nativeCRS = {I get the source native CRS here};
CoordinateReferenceSystem mapCRS = {I get Pseudo Mercator here};
List<SimpleFeature> features = {here is a list of features I need to
transform};
MathTransform transform = CRS.findMathTransform(nativeCRS, mapCRS, true);
features.parallelStream().forEach(feature -> {
try {
feature.setDefaultGeometry(JTS.transform((Geometry)
feature.getDefaultGeometry(), transform));
} catch(TransformException e) {
LOGGER.warn(e.getLocalizedMessage());
}
});
9. What is more strange, when I used Udig to view the data, they both fit.
I would be very grateful if someone could point mw what is wrong. If any
more data is needed - just let me know.
The server side uses Java 8 and Jboss 8 as an application server.
Best regards,
Marcin
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