REMOTE SENSING SOFTWARE
PRE-PROCESSING vs. POST-PROCESSING
The pre-processing involves all steps between the acquisition of the raw registrations (often called "segments") and the delivery of fully corrected composite images, with a daily (S1) or most often 10-daily (S10) time step. Each segment must be “ingested” (converted to standardized internal formats), calibrated, atmospherically and geometrically corrected, and each pixel’s observational state (clear, cloud, cloud shadow, snow, error...) must be labelled in an additional “status mask” image. Afterwards, S1 and/or S10 composites must be derived from all corrected segments in the concerned day or dekad.
The post-processing ingests the S1/S10 composites, delivered by the pre-processing, and creates a number of more specific, value-added products, mainly in the form of images, quicklooks and databases. The post-processing ends with the delivery of the final products to the client (in this case: JRC and Alterra).
MCYFS IMAGE PROCESSING SOFWARE
In practice this gives rise to the following three software tools:
VITO’s pre-processing software is written in C++ and running on LINUX machines. The individual C++ modules are concatenated to automated “chains" by means of the AppWorx software which steers the full processing, with time- or event-driven schedulers, automated loggings, optimized division of the tasks over the available machines, etc. The workload of the pre-processing (development and operation) varies with the sensor. While for SPOT-VGT fully pre-processed 10-daily composites are directly acquired from CTIV, for NOAA-AVHRR one has to start from the absolutely raw data. Other sensors such as METOP-AVHRR, TERRA-MODIS and the geostationary MSG occupy intermediate positions. The practical follow-up of the pre-processing is the task of the CTIV-operators at VITO. They also perform systematic and routine-based visual quality control checks for all MCYFS-products.
POST-PROCESSING with GLIMPSE
General GLIMPSE (Global Image Processing Software) is a set of image processing routines, developed over the years by the Applications-unit of VITO-TAP. The software is specifically designed for the post-processing of time series of daily, ten-daily or monthly composites, derived from low resolution sensors such as SPOT-VEGETATION, NOAA-AVHRR, METOP-AVHRR, TERRA-MODIS and MSG-SEVIRI. More specifically it allows for many operations such as spatial remapping, spectral rescaling and masking, compositing, time series analysis, and many others. Another important group of applications concerns the hard and soft (fuzzy) classification of any type of multi-temporal/spectral imagery. Most GLIMPSE modules are written in ultrafast ANSI-C, only some ad hoc routines are still in BASIC. The GLIMPSE software is permanently used (and adapted or extended) by VITO’s Applications-unit to fulfil the needs of important projects such as MARSOP (for EC-JRC), GMFS (ESA), ASIS (FAO) and many others, which involves the processing of terabytes of data. For the MCYFS, the full post-processing is realised via BAT-scripts which concatenate individual GLIMPSE modules into dedicated “processing chains”. Full automation is guaranteed by the regular activation of the chains with the Windows-Scheduler. Also at this level, all final products are quality checked by visual inspection.
GLIMPSE modules used for MCYFS The following tables give a concise description of the used modules. Note that GLIMPSE contains many more facilities.
How to obtain the GLIMPSE software? See SPIRITS (+LINK). The GLIMPSE executables can be found in the subfolder LIBS\GLIMPSE of the SPIRITS installation. The SPIRITS manual also provides detailed descriptions of all modules.
POST-PROCESSING with SPIRITS
SPIRITS (Software for the Processing and Interpretation of Remotely sensed Image Time Series) is developed by VITO since 2010 on behalf of the JRC-MARS unit. Written in JAVA, SPIRITS provides the necessary User Interfaces to access the GLIMPSE programs via modern Windows-based techniques, adapted to a wider public. Apart from GLIMPSE, SPIRITS provides a number of additional tools dealing with the import of (and export to) external formats, the storage and visualisation of derived information in databases, the generation of maps, and many more. A major objective is to provide all tools to generate the necessary information to include in agro-meteorological bulletins for any region in the world.
Role of SPIRITS in MCYFS SPIRITS is an important side-product, focusing on interactive use, but de facto it is not used as such in the MCYFS processing. In reality, the post-processing chains are operated via the GLIMPSE software (+LINK). How to obtain the SPIRITS software? The SPIRITS software comes together with a manual, help functionality, tutorials and associated data sets. It also includes the executables of the GLIMPSE software (in folder LIBS\GLIMPSE).
The entire package can be freely downloaded via: http://spirits.jrc.ec.europa.eu/. This website also provides a discussion forum, FAQs and an overview of training sessions.