topo-descriptors 0.2.0

A library to compute DEM-based topographical descriptors.

topo-descriptors

A python library to compute DEM-based topographical descriptors.

Usage

Let's install topo-descriptors with few additional packages that will help us to run a simple example:

pip install topo-descriptors
pip install elevation
pip install rasterio

elevation is an python library that provides an easy access to global elevation data. Here we are going to clip the SRTM 30m DEM around the Basodino region in southern Switzerland, around 46.4N 8.5E:

eio clip -o Basodino-30m-DEM.tif --bounds 8.2 46.30 8.6 46.55

Now in python we can use the xarray interface to rasterio to easily import our Basodino-30m-DEM.tif file:

import xarray as xr

dem = xr.open_rasterio("Basodino-30m-DEM.tif")
dem = dem.isel(band=0, drop=True)
dem.plot()

With the DEM data imported as a xarray DataArray, we can use topo-descriptors to compute two established topographical descriptors: the topographical position index (TPI) and the Sx. The TPI describes the elevation of a given point relatively to its neighbourhood, here defined on a 500 meter scale:

from topo_descriptors import topo, helpers

scale_meters = 500
scale_pixel, __ = helpers.scale_to_pixel(scale_meters, dem)
topo.tpi(dem, scale_pixel).plot(vmin=-100, vmax=100, cmap="bwr")

The Sx is used to describe the horizon in a given direction and spatial scale. In the example below we compute the Sx for a 0° azimuth (i.e., looking North) and a radius of 500 meters.

sx_500m = topo.sx(dem, azimuth=0, radius=500)
xr.DataArray(sx_500m, coords=dem.coords).plot.imshow()

Other topographical descriptors are available, such as slope, aspect, derivatives, and more.

======= History

0.2.0 (2021-06-12)

• Add Sx descriptor.
• Add STD descriptor.

0.1.2 (2021-05-14)

• First working release on PyPI.