GeoToolkit: convert from GPS to Lambert Conformal Conic

Question

I have to transform GPS coordinates (latitude and longitude) to a Lambert Conformal Conic projection. The map refers to Italy. Since I'm not an expert of this subject I found (googling) that one of the best libraries for Java is GeoToolkit. Unfortunately, I found no examples nor documentation (only Javadoc). Here the projection parameters (proj=Lcc Lat_2=45 Lat_1=40 Lat_0=42.5 Lon_0=9.2 x_0=600000 y_0=2200000):

PARAM_MT["Lambert_Conformal_Conic_2SP", 
PARAMETER["semi_major", 6378137.0], 
PARAMETER["semi_minor", 6356752.314], 
PARAMETER["central_meridian", 9.2], 
PARAMETER["latitude_of_origin", 42.5], 
PARAMETER["false_easting", 600000.0], 
PARAMETER["false_northing", 2200000.0], 
PARAMETER["standard_parallel_2", 45.0], 
PARAMETER["standard_parallel_1", 40.0]]

Does anyone knows a better library than GeoToolkit?

I wrote the following code to convert coords:

// 1. Get the MathTransform Factory
MathTransformFactory factory;

FactoryRegistry registry = new FactoryRegistry(
        MathTransformFactory.class);

factory = registry.getServiceProvider(MathTransformFactory.class, null,
        null, Hints.MATH_TRANSFORM_FACTORY);

// 2. Define source and target coord reference systems
GeographicCRS sourceCRS = DefaultGeographicCRS.WGS84;

ParameterValueGroup parameters = factory
        .getDefaultParameters("Lambert_Conformal_Conic_2SP");
parameters.parameter("semi_major").setValue(WGS84_AXIS_MAJOR);
parameters.parameter("semi_minor").setValue(WGS84_AXIS_MINOR);
parameters.parameter("central_meridian").setValue(9.2);
parameters.parameter("latitude_of_origin").setValue(42.5);
parameters.parameter("standard_parallel_1").setValue(40.0);
parameters.parameter("standard_parallel_2").setValue(45.0);
parameters.parameter("false_easting").setValue(600000);
parameters.parameter("false_northing").setValue(2200000);

// 3. Create the MathTransform with the given parameters
Conversion conversion = new DefiningConversion("GPS to Lambert",
        parameters);

CRSFactory crsFactory = FactoryFinder.getCRSFactory(null);
Map<String, ?> properties = Collections.singletonMap(
        ProjectedCRS.NAME_KEY, "LatLon2Lambert");
ProjectedCRS targetCRS = crsFactory.createProjectedCRS(properties,
        sourceCRS, conversion, DefaultCartesianCS.GENERIC_2D);

MathTransform tr = CRS.findMathTransform(sourceCRS, targetCRS);

DirectPosition sourcePt = new DefaultDirectPosition(DefaultGeographicCRS.WGS84);
sourcePt.setOrdinate(0, 45.0);
sourcePt.setOrdinate(1, 8.0);

DirectPosition targetPt = tr.transform(p.getValue(), null);

However, it doesn't work. Where am I wrong? Thanks in advance.

baronKarza baronKarza · Accepted Answer · 2012-05-15T06:49:56

The presented code is correct. The only problem is the input: GeoToolkit use a positional notation to identify latitude and longitude. And it requires that the first parameter is longitude. For example, at the end of the above code, you can perform the transformation.

The following is an example:

DirectPosition sourcePt = new GeneralDirectPosition(DefaultGeographicCRS.WGS84);
sourcePt.setOrdinate(0, Double.parseDouble(8.751426)); // longitude
sourcePt.setOrdinate(1, Double.parseDouble(45.12478)); // latitude

DirectPosition targetPt = tr.transform(p.getValue(), null);

In the targetPt variable you have the correct coordinates in Lambert.

GeoToolkit: convert from GPS to Lambert Conformal Conic

1 Answers