Context and objectives
The objective is to develop 10-day composite images of Vegetation's spectral bands. The method is called MC-FUME (Median Composite of FUzzy multispectral Estimate).
The objective of compositing remotely sensed images is to eliminate as much as possible all perturbing factors, disturbing the pure Top-of-Canopy signal at a certain observation geometry from the surface, such as clouds and cloud shadow, anisotropy of the surface, composition of the atmosphere etc. Within a 10 day period changes in ground cover are assumed to remain stable (except of course in case of phenomena that change dramatically the face of the earth in a very short time, such as floodings, snowfall or wildfires). In the case where stability of the surface can be assumed, we can use 10 images to extract a reference image for the period considered. The ten day period also gives us a fair chance of at least one cloud free image over most regions of the world.
The innovative approach of the project is in the fact that where the usual way to proceed is to combine the spectral information into a vegetation index, and select on the basis of that criterion a certain image, we try first to select an image for a certain spectral band, after which a vegetation index may be constructed.
Expected scientific results
The ouput of the method consists of estimates of TOC values of the earth's surface at a reference observation geometry over a period of 10 days for the RED and the NIR channel of the Vegetation sensor. These are produced from cloud masked, VGT-P products.
The method has been compared to the most applied compositing method, known as the MVC-NDVI. The MVC-NDVI method still exhibits a large amount of correlation between the observation geometry and the reflectance in the individual reflective channels of the Vegetation sensor in the composite image. With the new method, this correlation is removed to a very large extent, which means that the reflectances in each of the spectral channels of the composite image, are free of effects ocurring due to changing observation geometry in the 10 day period, and thus can more easily be compared. If maps of the individual reflective channel were to be made, MVC-NDVI would introduce a fairly large amount of 'speckle', due to its dependence on observation geometry, while MC-FUME maps would be speckle free. This has been proven, and reported in a paper to appear in the leading journal "IEEE : Transactions on Geoscience and Remote Sensing", where it passed extensive peer review
|Project leader(s):||VITO - Remote Sensing - Teledetectie en aardobservatieprocessen|