Hi Heiko:
the problem is that lat/lon boxes dont work well for polar projections. We have
a framework to add specializations, using a method on
ucar.unidata.geoloc.ProjectionImpl:
/**
* Convert a lat/lon bounding box to a world coordinate bounding box,
* by finding the minimum enclosing box.
* Handles lat/lon points that do not intersect the projection panel.
*
* @param latlonRect input lat,lon bounding box
* @return minimum enclosing box in world coordinates, or null if no part of
the LatLonRect intersects the projection plane
*/
public ProjectionRect latLonToProjBB(LatLonRect latlonRect);
if you have source, you can see what the generic algorithm does. We have one
projection (VerticalPerspective) that overrides it. A similar override should be
done in Stereographic (I think thats the one you use?).
It would be great to have some code that we can fit into this. let me know if
this makes sense.
thanks!
Heiko Klein wrote:
Hi,
I just tested the 4.0 snapshot Ethan send me last week. I see, you put
some effort testing if the pole is inside the dataset and the
bounding-box is now:
<lonLatEnvelope srsName="WGS84(DD)">
<gml:pos>-76.99999999999999 28.263336016688474</gml:pos>
<gml:pos>153.9644871012531 90.0</gml:pos>
</lonLatEnvelope>
So, one of 4 points is as I expect ;-) The values are stable, that is
the problem with axes in m seems to have disappeared.
I don't think it is possible to detect the bounding-boxes 'correctly' by
just projecting the corner-points. I would either project the axes and
use some polygons, or map the complete data-region. But this is of
course a greater computational effort. If you're interested, I can try
to come up with some code.
Best regards,
Heiko
John Caron wrote:
Ah yes, thanks, that makes a lot of sense. We've had a lot of trouble
getting the km/m conversion correct. Ill try to get it fixed.
Heiko Klein wrote:
Hi,
I just made another observation: when changing the units of the
projection_?_axis from m to km, the results are stable and stay those
of the first try.
Heiko
Heiko Klein wrote:
Hi,
I have a file with gridded polar-stereographic data in CF-1.0, which
shows nicely in IDV. When putting the file on thredds and requesting
WCS
GetCapabilites, I receive the following:
First try:
<lonLatEnvelope srsName="WGS84(DD)">
<gml:pos>-77.0 43.95245311362685</gml:pos>
<gml:pos>103.0 43.95245311362685</gml:pos>
</lonLatEnvelope>
Second try:
no envelope
Third try:
<lonLatEnvelope srsName="WGS84(DD)">
<gml:pos>-32.0 90.0</gml:pos>
<gml:pos>-32.0 90.0</gml:pos>
</lonLatEnvelope>
And it stays at the values of the third try, which are the definitions
of the projections (polar-stereographic, view at -32 degree) rather
than
the envelope.
The data spans over the northpole, so longitude is from 0-360 while
latitute starts at 90 and has a minimum value of 43 degree.
The file can be found at ftp://ftp.met.no/pub/emep/heikok/testShort.nc
(1.6MB)
I'm running thredds 3.16 on linux with java 1.6 and tomcat 6
Does anybody know how I can solve the problem of the wrong envelope?
Best regards,
Heiko
