Topography

The topography module provides interfaces to global elevation models. So far, only an interface to the SRTM30 data set is provided, which has a resolution of 1 km.

Elevation data is downloaded on the fly but is cached to speed up subsequent access. The interfaces uses the path pointed to by the TYPHON_DATA_PATH environment variable as data cache. This means that data is downloaded only when they are not found in the cache.

Note

If TYPHON_DATA_PATH is not set, the location of the file cache will be determined from the XDG_CACHE_HOME environment variable and, if this is not defined, default to :${HOME}/.typhon/topography.

The module can be used in two ways:

by extracting the elevation data at native resolution
by interpolating to elevation data at arbitrary locations

The two different use cases are described below.

Native resolution

Extracting elevation data at native resolution for a given rectangular domain: is done using the SRTM30.elevation function. The function returns a tuple consisting of the latitude and longitude grids as well as the elevation data in meters.

lat_min = 50
lon_min = 10
lat_max = 60
lon_max = 20
lats, lons, z = SRTM30.elevation(lat_min, lon_min, lat_max, lon_max)

Interpolation to given coordinates

Interpolation of the elevation data to arbitrary coordinates can be performed using the interpolate method. Interpolation uses nearest neighbor interpolation and is implemented using a KDTree. Interpolating the SRTM30 data to given latitude and longitude grids can be done as follows:

lat_min = 50
lon_min = 10
lat_max = 60
lon_max = 20
lats = np.linspace(lat_min, lat_max, 101)
lons = np.linspace(lon_min, lon_max, 101)
z = SRTM30.interpolate(lat, lont)