GDEM assessment

Short title:  GDEMerr

A methodological framework for assessment of accuracy of a DEM product is described using four case studies (Booschord in the Netherlands, Calabria in Italy, Fishcamp in USA and Zlatibor in Serbia). Focus is put on evaluating the true accuracy of ASTER GDEM using LiDAR data aggregated to 30 m resolution. Three aspects of accuracy have been evaluated: (a) ab­solute accur­acy of elevations (goodness of fit between true and GDEM eleva­tions), (2) accuracy of stream networks (goodness of fit for buffer distance maps for stream networks), and (3) accuracy of surface roughness parameters (goodness of representation of nug­get vari­ation and residual errors).

Purpose and use: 

Procedures are explained how to assess:

  • Accuracy of absolute elevations (absolute error);
  • Positional and attribute accuracy of hydrological features (streams, watersheds, landforms etc);
  • Accuracy of surface roughness (i.e. representation fo the short-range variation);

The script is attached to the paper indicated below.

Programming environment:  R / S language
Status of work:  Public Domain
Reference:  How accurate and usable is GDEM? A statistical assessment of GDEM using LiDAR data
Data set name: Fishcamp



  • "International Society for Geomorphometry (ISG) is a non-commercial, nongovernmental association of researchers and experts that are open for free exchange of knowledge and opinions about various aspects of DEM processing and Digital Terrain Modeling."

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