// create a new srtm data instance.
// it accepts a folder to download and cache data into in addition to the source you want to use for the data.
// USGS data is immediately available, but is of a lower resolution.
var srtmData = new SRTMData(@"/path/to/data/cache", new USGSSource());
// NASA data is of a higher resolution, but requires creating an account at https://urs.earthdata.nasa.gov/users/new/.
var credentials = new NetworkCredential("username", "password");
var srtmData = new SRTMData(@"/path/to/data/cache", new NASASource(credentials));

// get elevations for some locations
int? elevation = srtmData.GetElevation(47.267222, 11.392778);
Console.WriteLine("Elevation of Innsbruck: {0}m", elevation);

elevation = srtmData.GetElevation(-16.5, -68.15);
Console.WriteLine("Elevation of La Paz: {0}m", elevation);

elevation = srtmData.GetElevation(27.702983735525862f, 85.2978515625f);
Console.WriteLine("Elevation of Kathmandu {0}m", elevation);

elevation = srtmData.GetElevation(21.030673628606102f, 105.853271484375f);
Console.WriteLine("Elevation of Ha Noi {0}m", elevation);

// if a smoother result is preferred, it is possible to use bilinear interpolation at the cost of some accuracy
double? smoothElevation = srtmData.GetElevationBilinear(47.267222, 11.392778);
Console.WriteLine("Elevation of Innsbruck: {0}m", elevation);

smoothElevation = srtmData.GetElevationBilinear(-16.5, -68.15);
Console.WriteLine("Elevation of La Paz: {0}m", elevation);

smoothElevation = srtmData.GetElevationBilinear(27.702983735525862f, 85.2978515625f);
Console.WriteLine("Elevation of Kathmandu {0}m", elevation);

smoothElevation = srtmData.GetElevationBilinear(21.030673628606102f, 105.853271484375f);
Console.WriteLine("Elevation of Ha Noi {0}m", elevation);