How to convert coordinates from Gauss-Krueger to Longitude/Latitude?

Question

I'm a newbie in the GIS world so please advise me :)

In my .NET/C# project I need to show some shapes/points on the Bing Map. The problem is I have the Gauss-Krueger coordinates and need to convert them to Longitude/Latitude.

Can anyone point me to the right direction please? Is there maybe a free managed library for this purpose? A link with a good explanation of conversion algorithm would be helpful too.

Thanks!

Anil

Answer 1

I see you are from Sarajevo so you are probably need to convert GK coordinates from B&H coordinate system. First you will need to get transformation parameters for your area. I don't think there are any good one in EPSG database. Maybe you can use this one. I sometimes use them for area of Croatia. Regarding the C# lib, there is one which I used Proj4Net. Here is one my old example.

        CoordinateSystemFactory cFac = new CoordinateSystemFactory();
        Wgs84ConversionInfo par = new Wgs84ConversionInfo(514.0188, 155.448, 507.0461, 5.6136, 3.676, -11.4667, 2.091);
        IEllipsoid ellipsoid = cFac.CreateEllipsoid("Bessel 1840", 6377397.155, 6356078.963, LinearUnit.Metre);
        IHorizontalDatum Bessel1840 = cFac.CreateHorizontalDatum("Bessel 1840", DatumType.HD_Classic, ellipsoid, par);
        IGeographicCoordinateSystem gcsBessel = cFac.CreateGeographicCoordinateSystem("Bessel 1840", AngularUnit.Degrees, Bessel1840, PrimeMeridian.Greenwich,
            new AxisInfo("East", AxisOrientationEnum.East), new AxisInfo("North", AxisOrientationEnum.North));

        System.Collections.Generic.List<ProjectionParameter> parameters6 = new System.Collections.Generic.List<ProjectionParameter>(5);
        parameters6.Add(new ProjectionParameter("latitude_of_origin", 0));
        parameters6.Add(new ProjectionParameter("central_meridian", 18));
        parameters6.Add(new ProjectionParameter("scale_factor", 0.9999));
        parameters6.Add(new ProjectionParameter("false_easting", 6500000));
        parameters6.Add(new ProjectionParameter("false_northing", 0));


        IProjection projection6 = cFac.CreateProjection("Transverse Mercator", "Transverse_Mercator", parameters6);

        IProjectedCoordinateSystem zona6Bessel = cFac.CreateProjectedCoordinateSystem("6 zona Bessel", gcsBessel, projection6, LinearUnit.Metre, new AxisInfo("East", AxisOrientationEnum.East), new AxisInfo("North", AxisOrientationEnum.North));
        IGeographicCoordinateSystem wgs84 = GeographicCoordinateSystem.WGS84;

        CoordinateTransformationFactory ctFac = new CoordinateTransformationFactory();
        ICoordinateTransformation zona6ToWGS84 = ctFac.CreateFromCoordinateSystems(zona6Bessel, wgs84);

toPoint = zona6ToWGS84.MathTransform.Transform(fromPoint);

I hope this helps a little. This code was written a long time ago but i think it works. You just have to insert your parameters.

Answer 2

Look into GDAL. For a shapefile, the conversion command will be something like:

ogr2ogr -f "ESRI Shapefile" output.shp -t_srs EPSG:4326 -s_srs EPSG:31468 input.shp

Bindings for GDAL in C#: http://trac.osgeo.org/gdal/wiki/GdalOgrInCsharp

Answer 3

If you can perform the transformation client-side, you can take advantage of Proj4JS (user guide) which is a Javascript port of the underlying Proj.4 library.

If you're doing this Server-side there's a C# wrapper for Proj.4 which could also be used. If this is a conversion that doesn't need to be done dynamically, then using GDAL as glennon mentioned is the easiest approach.

If you need to look up an EPSG code, try spatialreference.org.

Answer 4

Thank you all for your fast answers!

Browsing through all the links you provided finally led me to http://dotspatial.codeplex.com

IMHO I found this one to be the easiest to use (add reference to single assembly DotSpatial.Projections.dll and start using it).

Answer 5

I had a same issue,

this is code example in c# using dotspatial.codeplex.com library

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using DotSpatial.Projections;

namespace GKtoWGS84
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            double[] xy = new double[2];
            double[] z = new double[1];
            ProjectionInfo pStart = new ProjectionInfo("+proj=tmerc +lat_0=0 +lon_0=18 +k=0.9999 +x_0=6500000 +y_0=0 +ellps=bessel +towgs84=550.499,164.116,475.142,5.80967,2.07902,-11.62386,0.99999445824 +units=m");
            ProjectionInfo pEnd = KnownCoordinateSystems.Geographic.World.WGS1984;

            xy[0] = 6448000;    
            xy[1] = 4880000;
            z[0] = 1;
            Reproject.ReprojectPoints(xy, z, pStart, pEnd, 0, 1);
        }

    }
}

description of gausskruger and MGI Balkans (Bosnian language) http://free-ri.htnet.hr/geocaching/_private/gausskruger.htm

another example http://dotspatial.codeplex.com/wikipage?title=Projecting%20to%20USA%20Contiguous%20Lambert%20Conformal%20Conic&referringTitle=UseKnownCoordinateSystems