By Tom Kiptenai
Land cover mapping using freely available optical remote sensing imagery is often hampered by high cloud cover. Kenya is no exception and the mapping of coastal Kenya is greatly hindered by this. To resolve and counter this problem, organisations and people are adopting the use of Synthetic Aperture Radar (SAR).
Data availability, especially the global coverage of free Sentinel-1 data, offers an unprecedented opportunity for research and design (R&D). In recent time more people and organizations are using SAR data in their work. SAR is an active sensor that can "see" through darkness, clouds and rain, detecting changes in habitat, levels of water and moisture, effects of natural or human disturbance and general changes in the Earth’s surface after events such as earthquakes or sinkhole openings.
In the Kenyan case, SAR is particularly useful in mapping and monitoring the tropical/sub-tropical regions or areas with monitoring difficulty due to cloud cover. This is a serious problem especially in the Kenyan coastal regions where finding a cloud-free Landsat imagery is impossible.
A SAR data processing training course for 11 government staff was supported by Conservation International through funding from Global Environmental Facility was held in Perth Australia at the Commonwealth Scientific and Industrial Research Organization (CSIRO) between the 6th May to 17th May 2019. The training covered the basic of SAR, scattering mechanisms, SAR sensor variations, how to access SAR data, SAR software and tools, SAR data pre-processing, configuration of SAR imagery, basic SAR processing and interpretation, among others.
With the lectures and hands-on practice, the following objectives were attained;
- Participants understood the basis of radar remote sensing
- Participants appreciated the features of SAR imagery and basic SAR image interpretation
- Participants understood the key SAR data processing steps
- Trainees became familiar with Sentinel-1 products and Sentinel-1 data access
- The technical team were able to use the Sentinel-1 Toolbox within ESA’s SNAP for SAR data processing
- Participants were capable of processing Sentinel-1 GRD and SLC data via GUI of Sentinel-1 Toolbox
Going forward, Kenya’s System for Land-Based Emission Estimation (SLEEK) Land Use/Land Cover (LULC) technical team is now equipped with knowledge on how to apply SAR imagery to address the issue of cloud in the coastal part of the country. However, they still need computing resources including fast, reliable internet, computers with higher computing power since SAR imagery are usually heavy.
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