Re: [Geotools-gt2-users] Behrmann Projection

[Peter B. <pet...@ya...>]

Hello-    I'm sorry if my previous note was unclear. I would like to implement the Cylindrical Equal Area projection:

http://www.remotesensing.org/geotiff/proj_list/cylindrical_equal_area.html

In doing so, GeoTools would be able to support other equal area projections like NSIDC EASE-Grid Global (EPSG:3410), Behrmann (EPSG:54017), Peters, Gal, etc.
I am a geotools novice but would like to contribute. What is the process for adding a new projection? 

I believe the first step is to implement a class that extends MapProjection. This code looks like a good place to start:
http://trac.osgeo.org/proj4j/browser/trunk/src/main/java/org/osgeo/proj4j/proj/CylindricalEqualAreaProjection.java
What else needs to be done?

Thanks,Peter


     From: Peter Borissow <pet...@ya...>
 To: Geotools-gt2-users <geo...@li...> 
 Sent: Thursday, March 19, 2015 7:07 PM
 Subject: Re: Behrmann Projection
   

Judging by the classes in the org.geotools.referencing.operation.projection package, it doesn't appear that GeoTools supports Cylindrical Equal Area projections:
https://github.com/geotools/geotools/tree/master/modules/library/referencing/src/main/java/org/geotools/referencing/operation/projection

Any hints on how to implement a Cylindrical Equal Area projection? 

I have stubbed out a CylindricalEqualArea class that extends MapProjection and assigned it to the org.geotools.referencing.operation.projection package.
What else should I do? Is there some way to register the class? 

Also, I noticed that most of the projections have a static class called "Provider" that extends "AbstractProvider". The Provider class has a ParameterDescriptorGroup with keywords for OGC, ESRI, EPSG, etc. 
There is also a GEOTOOLS key. For example, the EquidistantCylindrical class has something like this:

                new NamedIdentifier(Citations.GEOTOOLS, Vocabulary.formatInternational(
                                    VocabularyKeys.EQUIDISTANT_CYLINDRICAL_PROJECTION))

I guess I need to add an entry in VocabularyKeys as well?
Anything else?

Thanks in advance,Peter



 

     From: Peter Borissow <pet...@ya...>
 To: Geotools-gt2-users <geo...@li...> 
 Sent: Thursday, March 19, 2015 1:27 PM
 Subject: Re: Behrmann Projection
   

Quick update. I tried to hand code the Behrmann projection using a "Cylindrical_Equal_Area" with a standard parallel of 30 degrees: 

        String behrmannWKT = 
        "PROJCS[\"World_Behrmann\"," +
            "GEOGCS[\"GCS_WGS_1984\"," +
                "DATUM[\"WGS_1984\"," +
                    "SPHEROID[\"WGS_1984\",6378137,298.257223563]]," +
                "PRIMEM[\"Greenwich\",0]," +
                "UNIT[\"Degree\",0.017453292519943295]]," +
            "PROJECTION[\"Cylindrical_Equal_Area\"]," +
            "PARAMETER[\"False_Easting\",0]," +
            "PARAMETER[\"False_Northing\",0]," +
            "PARAMETER[\"Central_Meridian\",0]," +
            "PARAMETER[\"Standard_Parallel_1\",30]," +
            "UNIT[\"Meter\",1]," +
            "AUTHORITY[\"EPSG\",\"54017\"]]";

        CoordinateReferenceSystem crs = CRS.parseWKT(behrmannWKT);
Throws:
org.opengis.referencing.NoSuchIdentifierException: No transform for classification "Cylindrical_Equal_Area".

Does geotools support any Cylindrical Equal Area Projections?
http://www.remotesensing.org/geotiff/proj_list/cylindrical_equal_area.html


 

     From: Peter Borissow <pet...@ya...>
 To: Geotools-gt2-users <geo...@li...> 
 Sent: Thursday, March 19, 2015 12:14 PM
 Subject: Behrmann Projection
   
Hello-    I would like to create a map using the Behrmann Equal Area Projection (EPSG:54017). GeoTools doesn't seem to like this projection. When I call CRS.decode("EPSG:54017") I'm getting the following exception:

org.opengis.referencing.FactoryException: Error in "PROJECTION": No transform for classification "Behrmann".

When I try to pass in a Proj4 style string but I get a different exception.

CRS.decode("+proj=cea +lon_0=0 +lat_ts=30 +x_0=0 +y_0=0 +datum=WGS84 +ellps=WGS84 +units=m +no_defs")

Throws:

org.opengis.referencing.NoSuchAuthorityCodeException: No authority was defined for code "+PROJ=CEA +LON_0=0 +LAT_TS=30 +X_0=0 +Y_0=0 +DATUM=WGS84 +ELLPS=WGS84 +UNITS=M +NO_DEFS". Did you forget "AUTHORITY:NUMBER"?

Any suggestions?

Thanks,Peter


Related links:http://spatialreference.org/ref/esri/54017/http://mathworld.wolfram.com/BehrmannCylindricalEqual-AreaProjection.html
http://sourceforge.net/p/geoserver/mailman/message/24472263/