It sounds like the data is not actually in EPSG:4326 LAT/LON order then,
thus the renderer is getting confused by the fact that the CRS claims to be
a NORTH_EAST projection when the data isn't. In general avoid using
EPSG:4326 unless you are very sure that is what you have and you are sure
about the axis order (usually, to the extent of checking the axis order
while writing the coordinates into the geometries). You never know what the
user may have set the hints to until you get there.
Ian
On Tue, 28 Apr 2020 at 14:35, David Adler <dwa12...@gmail.com> wrote:
> A DB2 sample program that displays a map based on spatial data in a DB2
> table used to work but no longer works when I tried it recently. It just
> fails to display anything.
>
> It seems to be related to the AXIS ordering in the CRS which is different
> depending on whether one uses CRS.decode("EPSG:4326) or CRS.parseWKT(wkt)
> where wkt is the string representation of EPSG 4326. I fixed the problem by
> changing the DB2 code to use CRS.parseWKT instead of CRS.decode with "org"
> and "orgid". Shouldn't it work both ways?
>
> The following is my analysis of the problem:
>
> Using CRS.decode("EPSG:4326")
> results in
> GEOGCS["WGS 84",
> DATUM["World Geodetic System 1984",
> SPHEROID["WGS 84", 6378137.0, 298.257223563,
> AUTHORITY["EPSG","7030"]],
> AUTHORITY["EPSG","6326"]],
> PRIMEM["Greenwich", 0.0, AUTHORITY["EPSG","8901"]],
> UNIT["degree", 0.017453292519943295],
> AXIS["Geodetic latitude", NORTH],
> AXIS["Geodetic longitude", EAST],
> AUTHORITY["EPSG","4326"]]
>
> In StreamingRenderer.paint
> CRS.getAxisOrder(mapCRS) returns CRS.AxisOrder.NORTH_EAST
> which executes the following code which flips the AffineTransform in
> WorldToScreen which completely messes up the subsequent transformation
> from world to screen coordinates, causing them to be outside the
> clip area.
> if (CRS.getAxisOrder(mapCRS) == CRS.AxisOrder.NORTH_EAST) {
> try {
> // sanitize, having flipped axis causes slowdowns, the
> rendering
> // subsystem has to go from data to rendering to screen
> flipping axis order
> // twice when advanced projection handling is enabled
> Integer code = CRS.lookupEpsgCode(mapCRS, false);
> if (code != null) {
> String srs = "EPSG:" + code;
> CoordinateReferenceSystem earthNorthCRS =
> CRS.decode(srs, true);
> mapArea =
> new ReferencedEnvelope(
> mapArea.getMinY(),
> mapArea.getMaxY(),
> mapArea.getMinX(),
> mapArea.getMaxX(),
> earthNorthCRS);
> }
>
> // flip world to screen too
> worldToScreen =
> new AffineTransform(
> worldToScreen.getShearX(),
> worldToScreen.getScaleX(),
> worldToScreen.getScaleY(),
> worldToScreen.getShearY(),
> worldToScreen.getTranslateX(),
> worldToScreen.getTranslateY());
> } catch (Exception e) {
> LOGGER.log(
> Level.FINER,
> "Failed to turn the requested bbox in east/north
> order, map rendering "
> + "should work anyways, but pay a
> performance price");
> }
>
> Creating the CRS from WKT, everything works fine.
> CRS from CRS.decodeWKT(wkt)
> GEOGCS["GCS_WGS_1984",
> DATUM["D_WGS_1984",
> SPHEROID["WGS_1984", 6378137.0, 298.257223563]],
> PRIMEM["Greenwich", 0.0],
> UNIT["degree", 0.017453292519943295],
> AXIS["Longitude", EAST],
> AXIS["Latitude", NORTH]]
>
> _______________________________________________
> GeoTools-GT2-Users mailing list
> GeoTools-GT2-Users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/geotools-gt2-users
>
--
Ian Turton
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