Delivering AATSR data to Australian users
Matt Paget(1) and Edward King(1)
GPO Box 3023,
Canberra, ACT, 2601,
The Earth Observation Centre (EOC) is tasked with the collation and dissemination of remote sensing data sets for the Commonwealth Science and Industry Research Organisation (CSIRO) in Australia. The EOC focuses its activities towards providing high quality, consistently processed and relevant data sets to CSIRO researchers and external clients. The EOC’s current holdings include a 20-year time series of AVHRR data covering the entire Australasian region, and a full set of MODIS land images for Australia. Recently we have added AATSR Levels 1B and 2 data to CSIRO’s collection. This paper describes our processing and dissemination system for the AATSR archive.
With the progression towards well-calibrated and geolocated Earth observation data, as provided by AASTR, we aim to construct a generic system that is easily adapted for future instruments and data formats. We have found the PDS file format to be compact though not self-documenting, and users have reported difficulty in readily extracting the data they require without writing specific routines for each application, even with such tools as EnviView. We report on our rationale for converting PDS files to HDF and, in doing so, removing some of the data that common users may find confusing. This ensures that the Level 1B data can be used by anyone familiar with HDF, while in the conversion we retain as much of the native (PDS) metadata and syntax as possible. Our system is built on open source code with Perl master routines interfacing with a SQL database, binary operations in C, TCL/NAP for array manipulation and HDF(4) exporting, and a CGI web interface with OPeNDAP support. We gain only a small reduction in file size (due mostly to the data that we removed rather than the HDF format) but we find that benefits arise from enhanced ease-of-use, along with greater portability through the OPeNDAP protocol. The original PDS files are retained on original media so no information is lost.
The result is that the EOC AATSR archive caters to researchers who desire the raw (Level 1B) data but don’t have the time or resources to decode the contents of PDS files. Current research activities in CSIRO that are utilising AATSR data include: regional sea surface temperature; Antarctic glaciology; global land temperature, and; regional and national NDVI analysis. We expect further applications to arise as experience with this data set disseminates through the community. Finally, we also report on initial comparisons of NDVI time series for continental Australia from the AATSR, AVHRR and MODIS sensors.