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Mercator Projection

#1

I’m having some issues setting projections still.

All my data (shapefiles) come in WGS84 unprojected, with units in decimal degrees. I want to project all of these to standard mercator projection, which is -180 to +180 degrees left to right.

I THINK this is what I want: http://spatialreference.org/ref/epsg/wgs-84-world-mercator. I set it up like this:

Map.MapUnit = GeographyUnit.DecimalDegree;

ShapeFileFeatureLayer.BuildIndexFile(mainShapeFilePath, BuildIndexMode.DoNotRebuild);
ShapeFileFeatureLayer worldLayer = new ShapeFileFeatureLayer(mainShapeFilePath);

Proj4Projection proj4Projection = new Proj4Projection();
proj4Projection.InternalProjectionParametersString = Proj4Projection.GetEpsgParametersString(4326);
proj4Projection.ExternalProjectionParametersString = Proj4Projection.GetEpsgParametersString(3395);
worldLayer.FeatureSource.Projection = proj4Projection;

However, the shapefile does not display correctly. What am I doing wrong?

#2

Hi Dan,

I guess you forget set the correct current extent for your shape.

You should want to call worldLayer.Open() and GetBoudingBox() to set it to current extent.

Regards,

Ethan

#3

Hi thanks for the reply. I was doing that actually, it still didn’t work.

string mainShapeFilePath = @"../../AppData/Merge_Countries.shp";
Map.MapUnit = GeographyUnit.DecimalDegree;

ShapeFileFeatureLayer.BuildIndexFile(mainShapeFilePath, BuildIndexMode.DoNotRebuild);
ShapeFileFeatureLayer worldLayer = new ShapeFileFeatureLayer(mainShapeFilePath);

Proj4Projection proj4Projection = new Proj4Projection();
proj4Projection.InternalProjectionParametersString = Proj4Projection.GetEpsgParametersString(4326);
proj4Projection.ExternalProjectionParametersString = Proj4Projection.GetEpsgParametersString(3395);
worldLayer.FeatureSource.Projection = proj4Projection;

AreaStyle areaStyle = new AreaStyle();
areaStyle.FillSolidBrush = new GeoSolidBrush(GeoColor.FromArgb(255, 233, 232, 214));
areaStyle.OutlinePen = new GeoPen(GeoColor.FromArgb(255, 118, 138, 69), 1);
areaStyle.OutlinePen.DashStyle = LineDashStyle.Solid;
worldLayer.ZoomLevelSet.ZoomLevel01.DefaultAreaStyle = areaStyle;
worldLayer.ZoomLevelSet.ZoomLevel01.ApplyUntilZoomLevel = ApplyUntilZoomLevel.Level20;
worldLayer.Name = "World Layer";

Map.Overlays.Add("World Overlay", worldOverlay);

worldLayer.Open();
Map.CurrentExtent = worldLayer.GetBoundingBox();
Map.RestrictedExtent = Map.CurrentExtent;
worldLayer.Close();

Map.Refresh();

Above is the full code.
Below is the shapefile I’m testing.

testShapefile.zip (2.5 MB)

#4

Hi Dan,

The “EPSG:3395” map unit is Meter, so you need to change the MapUnit to Meter as following statements:

winformsMap1.MapUnit = GeographyUnit.Meter;

Then it should display correctly.

image.png774×518 56.8 KB

Thanks
Mark

#5

Looks like it should work. I didn’t think changing the map units to meters would fix it but I forgot it’s taking the internal string and projecting it to the new projection, so it shouldn’t matter in the end.

Thank you very much!

#6

Hi Dan,

I am glad to hear that’s helpful.

Regards,

Ethan