Lac Bam Shown by TerraSAR-X - The Visualisation of Seasonal and Long Term Changes

Kurzfassung

The lake of Bam, located in northern Burkina Faso, is one of the most important water reservoirs for agriculture of semi-arid Africa. The area is also important for the local flora and fauna. Due to the annual increase in water extraction, the lake continues to dry out. The lake is part of the Ramsar program and is referred to as a "Wetland of International Importance". That is one of the reasons why the area is monitored by the TerraSAR-X satellite since 2013. The data set comprises more than hundred dual-co-polarized TerraSAR-X strip map acquisitions collected during the dry seasons with the highest possible temporal sampling of eleven days. All images are pre-processed by the exclusive MultiSAR system at DLR. This refinement applies calibration, geocoding, radiometric enhancement by multi-scale multi-looking and normalization to so-called Kennaugh elements. The last step guarantees the space-saving storing, the simple and effective classification and therewith, the understandable visualisation of this high-dimensional data. The task of this study is to evaluate the TerraSAR-X data of the last 5 years (2013-2018) and to visualise the obtained information for the main focal points, water and wetland areas: How did the water surface change, did the ecosystems get smaller and do they disappear faster over time? Is there also a change in farming detectable and has agriculture spread further inland due to the use of modern water extraction techniques? The goal is to check whether long-term consequences for the lake and its ecosystem are discernible. Besides that, contribution provides an impressive visualisation with up-to-date methods aiming at the automated mapping of land cover changes in the near future.