Hello Andrea- I have attached an updated copy of the CylindricalEqualArea class along with a test script. The CylindricalEqualArea class supports 2 "alias" projections:
- World Behrmann (ESRI:54017)- Lambert Cylindrical Equal Area
You will need to add 3 lines to the
org.geotools.referencing.operation.MathTransformProvider for it to work:
org.geotools.referencing.operation.projection.CylindricalEqualArea$Provider
org.geotools.referencing.operation.projection.CylindricalEqualArea$BehrmannProvider
org.geotools.referencing.operation.projection.CylindricalEqualArea$LambertCylindricalEqualAreaProvider
The CylindricalEqualArea class is supposed to support both spheriods and
ellipsoids. I have verified that the ellipsoidal calculations are correct using
the Behrmann projection (ESRI:54017) which uses the WGS84 ellipsoid.
Unfortunately, there appears to be something wrong with the spherical datums
like the one used by NSIDC EASE-Grid Global (EPSG:3410) which uses the 1924
Authalic Sphere. cs2cs reports that the coordinates in the x axis are correct
but the y axis is off. I have checked my code against the proj4 and proj4j
projects and I don't see what I'm doing wrong.
I am hesitant to put in a pull request because of this issue.
Options:
(1) Have someone from the GeoTools dev team review my code with the latest
version on GeoTools. Note that I am using an older version of GeoTools (10.x)
and an unknown build of proj4 (cs2cs utility) so the anomaly I am seeing with
spherical datums may be just a misconfiguration on my end.
(2) Comment out support for spherical datums.
Please let me know how you would like to proceed.
Thanks,Peter
From: Andrea Aime <andrea.a...@geo-solutions.it>
To: Peter Borissow <peter.boris...@yahoo.com>
Cc: Geotools-Devel list <geotools-devel@lists.sourceforge.net>
Sent: Sunday, March 29, 2015 10:13 AM
Subject: Re: [Geotools-devel] Cylindrical Equal Area Projection
On Sun, Mar 29, 2015 at 2:39 PM, Peter Borissow <peter.boris...@yahoo.com>
wrote:
I have attached a first cut of the CylindricalEqualArea projection.
You will need to add 2 lines to the
org.geotools.referencing.operation.MathTransformProvider for it to work:
org.geotools.referencing.operation.projection.CylindricalEqualArea$Provider
org.geotools.referencing.operation.projection.CylindricalEqualArea$BehrmannProvider
Hi Peter,normally we ask for a pull request to be made, could you create one?
There are instructions
here:http://docs.geotools.org/latest/developer/procedures/contribute.html#code-contributions
I don't know how to test it.
You have to write a script test, see the two commits I've linked for
examples.It's basically just getting some reference results from cs2cs and
build the script file that contains them, with tolerances.
Visually it looks ok. I used the following code which generated a map that
looks a lot like
this:http://mathworld.wolfram.com/BehrmannCylindricalEqual-AreaProjection.html
CoordinateReferenceSystem crs = CRS.decode("EPSG:54017");
MapContent map = new MapContent();
MapViewport vp = map.getViewport();
vp.setCoordinateReferenceSystem(crs);
map.addLayer(getPoliticalBoundaries());
map.addLayer(getGraticules());
I used code from Proj4j[1] which is almost identical to Proj4[2].
The only thing I'm not sure about is the "trueScaleLatitude" variable in the
constructor. In proj4, this maps to "tlat_ts". I have no idea what the
equivalent is in GeoTools.
I don't know what that is either. CheersAndrea
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Ing. Andrea Aime
@geowolfTechnical Lead
CylindricalEqualArea.java
Description: Binary data
// Test script for Cylindrical Equal Area projections //WGS84 Ellipsoid set _WGS84_ = GEOGCS["WGS 84",DATUM["WGS_1984",SPHEROID["WGS 84",6378137,298.257223563 ] ], PRIMEM["Greenwich",0.0], UNIT["degree",0.01745329251994328 ]] //1924 Authalic Sphere set _AuthalicSphere_ = GEOGCS["Unspecified datum based upon the International 1924 Authalic Sphere",DATUM["Not_specified_based_on_International_1924_Authalic_Sphere",SPHEROID["International 1924 Authalic Sphere",6371228,0, AUTHORITY["EPSG","7057"]],AUTHORITY["EPSG","6053"]], PRIMEM["Greenwich",0, AUTHORITY["EPSG","8901"]], UNIT["degree",0.01745329251994328, AUTHORITY["EPSG","9122"]], AUTHORITY["EPSG","4053"]] //NSIDC EASE-Grid Global (EPSG:3410) set _NSIDCGlobal_ = PROJCS["NSIDC EASE-Grid Global",_AuthalicSphere_,UNIT["metre",1,AUTHORITY["EPSG","9001"]],PROJECTION["Cylindrical_Equal_Area"],PARAMETER["standard_parallel_1",30],PARAMETER["central_meridian",0],PARAMETER["false_easting",0],PARAMETER["false_northing",0],AUTHORITY["EPSG","3410"],AXIS["X",EAST],AXIS["Y",NORTH]] //World Behrmann (ESRI:54017) set _Behrmann_ = PROJCS["World_Behrmann",_WGS84_,PROJECTION["Behrmann"], PARAMETER["False_Easting",0],PARAMETER["False_Northing",0],PARAMETER["Central_Meridian",0],UNIT["Meter",1],AUTHORITY["EPSG","54017"]] // -------------------------------------------------------------------------- // // WGS84 to Behrmann (ESRI:54017) // cs2cs -v +datum=WGS84 +proj=lonlat +to +proj=cea +lon_0=0 +lat_ts=30 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs // -------------------------------------------------------------------------- // source crs = _WGS84_ target crs = _Behrmann_ test tolerance = (0.001, 0.01) source pt = (0, 0) target pt = (0, 0) source pt = (10, 10) target pt = (964862.80, 1269436.74) source pt = (-50, -50) target pt = (-4824314.01, -5614050.10) // precision change with for higher lon values test tolerance = (0.01, 0.001) source pt = (130, 0) target pt = (12543216.43, 0.00) source pt = (130, 60) target pt = (12543216.43, 6351420.00) // -------------------------------------------------------------------------- // // Behrmann (ESRI:54017) to WGS84 // cs2cs -v +proj=cea +lon_0=0 +lat_ts=30 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs +to +datum=WGS84 +proj=lonlat // -------------------------------------------------------------------------- // source crs = _Behrmann_ target crs = _WGS84_ test tolerance = (0.0001, 0.0001) source pt = (0, 0) target pt = (0, 0) source pt = (964862.80, 1269436.74) target pt = (10, 10) source pt = (-4824314.01, -5614050.10) target pt = (-50, -50) source pt = (12543216.43, 0.00) target pt = (130, 0) source pt = (12543216.43, 6351420.00) target pt = (130, 60) // -------------------------------------------------------------------------- // // WGS84 to NSIDC EASE-Grid Global (EPSG:3410) // cs2cs -v +datum=WGS84 +proj=lonlat +to +proj=cea +lon_0=0 +lat_ts=30 +x_0=0 +y_0=0 +a=6371228 +b=6371228 +units=m +no_defs // -------------------------------------------------------------------------- // source crs = _WGS84_ target crs = _NSIDCGlobal_ test tolerance = (0.001, 0.01) source pt = (0, 0) target pt = (0, 0) source pt = (10, 10) target pt = (963010.77, 1277505.40) source pt = (-50, -50) target pt = (-4815053.87, -5635682.03) // precision change with for higher lon values test tolerance = (0.01, 0.001) source pt = (130, 0) target pt = (12519140.07, 0.00) source pt = (130, 60) target pt = (12519140.07, 6371228.00) // -------------------------------------------------------------------------- // // NSIDC EASE-Grid Global (EPSG:3410) to WGS84 // cs2cs +proj=cea +lon_0=0 +lat_ts=30 +x_0=0 +y_0=0 +a=6371228 +b=6371228 +units=m +no_defs +to -v +datum=WGS84 +proj=lonlat // -------------------------------------------------------------------------- // source crs = _NSIDCGlobal_ target crs = _WGS84_ test tolerance = (0.0001, 0.0001) source pt = (0, 0) target pt = (0, 0) source pt = (12519140.07, 6371228.00) target pt = (130, 60) source pt = (12519140.07, 0.00) target pt = (130, 0) source pt = (-4815053.87, -5635682.03) target pt = (-50, -50)
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