static void TestCountryPolygonAPI()
{
// test polygon API
string countryCode = "NGA";
double simplifyTolerlance = 0.0;
GeoMultiPolygon fullNigeriaData = GeoAPI.ReadGeoPolygonByCountryKey(countryCode, simplifyTolerlance);
if (fullNigeriaData == null)
{
Console.WriteLine("failed to get country data for specified country code: {0}", countryCode);
return;
}
fullNigeriaData.saveToGeoJson("E:/Full_Nigeria.geojson");
simplifyTolerlance = 0.02;
GeoMultiPolygon simplifiedNigeriaDataPreserveTopology = GeoAPI.ReadGeoPolygonByCountryKey(countryCode, simplifyTolerlance);
if (simplifiedNigeriaDataPreserveTopology == null)
{
Console.WriteLine("failed to get country data for specified country code: {0}", countryCode);
return;
}
// access lat long data
for (int i = 0; i < simplifiedNigeriaDataPreserveTopology.GetData().Count; i++)
{
GeoPolygon polygon = simplifiedNigeriaDataPreserveTopology.GetData()[i];
for (int j = 0; j < polygon.GetData().Count; j++)
{
GeoLineString lineString = polygon.GetData()[j];
for (int k = 0; k < lineString.GetData().Count; k++)
{
LonLat lonlat = lineString.GetData()[k];
Console.WriteLine("{0}d th x = {1}, y = {2}", i, lonlat.longitude, lonlat.latitude);
}
}
}
// how to test result
// we can save result to geojson file, open it in GIS tool(for example QGIS) and view it.
bool saveSuccess = simplifiedNigeriaDataPreserveTopology.saveToGeoJson("E:/Simplified_Nigeria_0.02.geojson");
if (!saveSuccess)
{
Console.WriteLine("failed to save");
}
}
public static GeoMultiPolygon ReadGeoPolygonByCountryKey(string iso3166_1CountryCode, double simplifyTolerlance, bool preserveTopology = true)
{
String sql = "SELECT geom FROM level0 WHERE GID_0 = " + "'" + iso3166_1CountryCode + "'";
Layer resultLayer = _dataSource.ExecuteSQL(sql, null, "");
if (resultLayer == null)
{
return(null);
}
if (resultLayer.GetFeatureCount(0) == 0)
{
return(null);
}
Feature feature = resultLayer.GetNextFeature();
Geometry geometry = feature.GetGeometryRef();
if (simplifyTolerlance > 0)
{
if (preserveTopology == true)
{
geometry = geometry.SimplifyPreserveTopology(simplifyTolerlance);
}
else
{
geometry = geometry.Simplify(simplifyTolerlance);
}
}
int geometryCount = geometry.GetGeometryCount();
wkbGeometryType geomType = geometry.GetGeometryType();
string[] options = new string[1];
string geometryJson = geometry.ExportToJson(options);
GeoMultiPolygon multiPoygon = new GeoMultiPolygon();
multiPoygon.SetData(geometry);
multiPoygon.SetGeoJson(geometryJson);
return(multiPoygon);
}