dem_error_study

Code and results of Hugonnet et al. (2022), Uncertainty analysis of digital elevation models by spatial inference from stable terrain. 🌐 🗻

Below a short guide to: perform the uncertainty analysis of your own data, retrieve the case study datasets, reproduce the processing steps with the case studies, reproduce the figures and tables of the paper.

Uncertainty analysis of your own data with xDEM

The results of this study are based on routines implemented in xDEM with documentation at https://xdem.readthedocs.io/. In particular, xDEM includes tutorials on DEM uncertainty analysis to:

• Estimate the heteroscedasticity of elevation errors (Heteroscedasticity gallery example here),
• Standardize elevation differences to use stable as an error proxy (Standardization gallery example here),
• Estimate spatial correlation of errors and propagate to uncertainties of volume change (Spatial correlation gallery example here).

Note at the date of 08.07.22: xDEM is still in development (version 0.0.6), and its documentation in construction. Some changes are ongoing or planned for the summer 2022, including:

• Construction of an error pipeline that combines all steps,
• Automate the retrieval of ICESat-2 data (using icepyx) to perform local uncertainty analysis,
• Streamlining of existing gallery example,
• Minor fixes and improvements of routines.

Retrieve the case study datasets

The dataset consists of:

1. Nearly-simultaneous Pléiades–SPOT-6 elevation differences at the Mont-Blanc massif and the Pléiades DEM used as a reference for alignment and deriving terrain attributes (.tif, ~200 MB) at 5 m posting available at TBC.
2. Nearly-simultaneous ASTER–SPOT-5 elevation differences at the Northern Patagonian Icefield at 30 m posting (.tif, ~50 MB) available at TBC.

Reproduce the processing steps with the case studies

Setup environment

Most scripts rely on the code assembled in the packages xDEM which in turns relies on SciKit-GStat.

You can rapidly install a working environment containing those packages and their dependencies with the environment.yml file, located at the root of the repository, using conda:

conda env create -f environment.yml

Further details on setup and functions present in these packages are available through xDEM's documentation and SciKit-GStat's documentation.

Note: Due to continuous development changes, xDEM is set to v0.0.6 to exactly reproduce the processing steps of the paper.

How to use

Scripts for reproducing the processing steps are located in case_study_montblanc/ or case_study_npi/. Those are generally quite short as they use one-liner routines of xDEM.

Some computations (e.g., simulation of correlated field) are performed only in the figures/ scripts. In the future, those might be integrated in xDEM.

Reproduce the figures and tables

Scripts for reproducing the figures and tables are located in figures/. In some occasions, those duplicate the processing steps done in case_study_montblanc/ or case_study_npi/ for plotting purposes (e.g., violin plots require the full distribution of samples, not only the binned estimates of dispersion).