Data examples

Data examples#

xDEM uses and proposes several data examples to manipulate and test the features and workflows.

Description#

The south of Longyearbyen, capital of Svalbard, a Norwegian archipelago, is the most used dataset in xDEM. It is composed of:

Alias	Filename	Type	Description
`"longyearbyen_ref_dem"`	DEM_2009_ref.tif	Raster	DEM of the area in 2010 (1)
`"longyearbyen_tba_dem"`	DEM_1990.tif	Raster	DEM of the area in 1990 (1)
`"longyearbyen_glacier_outlines"`	CryoClim_GAO_SJ_1990.shp	Vector	Glacier outlines in the Svalbard in 1990 (2)
`"longyearbyen_glacier_outlines_2010"`	CryoClim_GAO_SJ_2010.shp	Vector	Glacier outlines in the Svalbard in 2010 (2)
`"longyearbyen_epc"`	EPC_IS.gpkg	Point Cloud	Land elevation over the area measured between 2019 and 2021 (3)

Note

So, "longyearbyen_ref_dem" (for “reference” dem) can be compared to "longyearbyen_tba_dem" (for “to-be-aligned” dem).

Another data is available over the Giza pyramid complex:

Alias	Filename	Type	Description
`"giza_dem"`	DSM.tif	Raster	DEM of the area in 2013

Note

If you need more information about the data, you can read this page of the xdem-data github project where they are stored or the documentation associated with their Digital Object Identifier:

Access to data#

Python#

If you want to use one of the example data, you can run this function with the corresponding data alias:

import xdem

# Download the 2010 raster DEM Longyearbyen dataset in output_dir and return its path
path = xdem.examples.get_path("longyearbyen_ref_dem")

It downloads the entire dataset of the alias if it was not already available and returns its absolute file path.

Also, you can download all the data, no matter the area by running:

# Download all the of the xDEM data (Longyearbyen and Giza dataset) and return the output directory path
output_dir = xdem.examples.get_all_data()

In both case, you can specify the output_dir where you want that data to be download or searched:

output_dir = "/dir/my_output_dir"
path = xdem.examples.get_path("longyearbyen_ref_dem", output_dir=output_dir)
output_dir = xdem.examples.get_all_data(output_dir=output_dir)

Command line interface#

To experiment the Command line interface, you can also use the alias to refer data examples in the configuration file:

inputs:
  reference_elev:
    path_to_elev: "longyearbyen_ref_dem"
    path_to_mask: "longyearbyen_glacier_outlines_2010"
...

Workflows will automatically download and manage the needed data.

Bash#

To download the data samples, you can run:

mkdir data_examples
tar -xvz -C data_examples  --wildcards  "*/data" --strip-components 2 -f <(wget -q -O - https://github.com/GlacioHack/xdem-data/archive/ca0e87271925d28928526bbce200162f002d6a93.tar.gz)