Last Friday before leaving for the weekend, the PCI Geomatics Research and Development team set up a large mosaic processing task to test our new distributed job processing system.The test data consisted of 349 SPOT-5 B scenes (panchromatic, 2.5 m pixel size) that covered the province of Alberta from the extensive Iunctus Geomatics Corp. SPOT archive. The reference data was a Landsat derived mosaic of Alberta and a subset of road vectors from the Canadian Road Network data set.
Needless to say, we were very pleased to see that when we returned on Monday morning, that a high quality 2.5 m panchromatic mosaic of Alberta had been produced in just 51 hours and 20 minutes!
There were a number reasons that we are particularly pleased with the outcomes of this test. The first, and most obvious reason is that the overall mosaic is of such high quality. The neighborhood tone balancing was effective, with only few poor quality areas that were limited by availability of imagery without haze (and low dynamic range). The geometric accuracy was also very good, with 294 scenes having total GCP residual under 2.5 pixels.
In a production environment the unsatisfactory scenes would be corrected during the process suspension through manual GCP collection, or adjustment of their radiometry. If a scene was beyond repair it could easily be replaced with new data with the help of the mosaic update workflow.
We were also very pleased that it demonstrated the practical functionality of the distributed job processing system. By concurrently running multiple processing threads on four CPU servers with 15 simultaneous jobs running in the system, production rate was greatly enhanced.This system was created for a development project undertaken by PCI, Iunctus Geomatics Corp. and the Alberta Terrestrial Imaging Center (ATIC), and funded by Precarn Inc. and Alberta Advanced Education and Technology. The configuration of this particular processing system was designed to meet production throughput requirements of 800 scenes per week, in other terms, processing rates of 12.6 minutes per scene. We achieved a higher throughput rate (8.9 minutes per scene), using this system (a multi-CPU configuration with distributed job processing system). PCI offers a hardware accelerated system, the GeoImaging Accelerator; using this type of system the throughput would improve to 2.8 minutes per scene! That would have meant that the Alberta mosaic would have taken less than 1 day (16 hours!) to complete. If you are facing challenges processing diverse, high volume datasets in an automated manner, contact PCI Geomatics today!
