Data Processing

Source Data like Satellite Imagery, Elevation Models and Land Use Data as acquired from GAF’s Geo-Data Store and from other sources can be input to further pre-processing steps, extended quality control and database generation. GAF provides a complete range of services for the generation of databases including spatial and non-spatial data, integrating raster, vector, attribute, and multimedia data. Services range from data capture (scanning, digitizing, GPS based surveying, inventorying and field mapping), data compilation (mosaic and tile generation, spatial and geo-statistical analysis, data compression) and database conversion to database integration and integrity control. Strict quality control is the guiding principle for all database generation processing steps since data serve as "fuel" for all kinds of information systems. This removes the risk of "garbage in - garbage out" systems.

The increasing number and capacity of new generation VHR satellite imagery systems now allows the coverage of very large regions with 50cm to 2.5m colour imagery. Most applications require from that imagery to provide a very high positional accuracy and to be strictly quality-controlled. The vast amounts of data related to these large-area coverages can only be managed well, if dedicated and highly efficient workflows for the production and quality control are in place. We have developed such workflows and procedures, making use of our large experience in the field of satellite image processing since 1985. Furthermore we can assist the customer in finding appropriate ancillary data required for the orthorectification process, like best-possible Digital Elevation Models and adequate Ground Control. Areas exceeding 100.000 sqkm can be produced in reliable quality and with positional accuracies of a few meters - in short time.

Many applications require the coverage of very large areas with a continuous and homogeneous image product. Besides precise orthorectification, the mosaicking process has to be done with great care to minimize inhomogeneity of colours and the visibility of scene edges in the image product. Coverages can be achieved in many cases with a single sensor source, when the acceptable time-frame for new image acquisitions or archive data to be used is large enough. GAF’s experience in the production of single source mosaics covers a lot of different projects and systems, including the generation of country-wide Euro-Maps mosaics, as available in the Geo-Data Store. Sometimes, complete coverage of an area is required in a narrow time-frame and at very high resolution. In most of these cases, the use of multi-source VHR imagery is the only way to achieve this goal in due time. GAF has developed dedicated procedures and workflows to create continuous mosaics, as homogeneous as possible, from many different sources. The use of semi-automated procedures with manual expert input (where necessary) help to ensure the high quality standard, which is recognised to be characteristic for all GAF products. All mosaics can be delivered in projections, formats and tiling schemes according to the specific customer requirements.

Image Processing services at GAF include basic pre-processing and advanced correction and enhancement procedures for raw satellite data, creation of derived products like Digital Elevation Models as well as the production of mosaics and combined products. Since 1985 we have processed vast amounts of data scattered all over the globe, consisting of various commercial and scientific sensor data sources. Image and Raster Data Processing services at GAF are available as a single service for data provided by the customer, or can be embedded in a complete value-adding service ranging from the procurement of source data up to semi-automated image data analysis for land, marine and coastal applications. The process of Image Analysis links the pre-processed satellite data from optical and radar sources to the provision of extracted information to specific application areas. Satellite data are an objective and spatially contiguous representation of the properties of the earth's surface. Once gathered, multi-parametric satellite data has to be transformed into mapping or target information by way of an often complex and subjective process. At GAF we work with a number of applications with proven and established satellite data analysis methodologies, encompassing both automatic feature detection and interactive interpretation techniques. A strictly quality controlled, hybrid process, yields for most applications the most precise and economic results. Our credo is the ultimate importance of developing analysis procedures which are truly operational and, with minor modifications, can easily be scaled up.

The entire suite of state-of-the-art GIS-based geo-data processing and analysis is established at GAF since more than 20 years. Data processing includes quality assessment (geographic-topological, coordinate systems, attributive), data collection and extraction, data conversion for interoperability, metadata generation, digital cartography, and advanced spatial analysis and geo-statistics operations.

Further, geo-processing tools to automate GIS tasks for the processing of raster and vector data are developed at GAF. Especially for repetitive works involving multiple processing steps, methods to automate, document, and share multiple-step procedures - known as workflows or processing-chains - are developed, tested, and applied. Not only for the execution of mass production projects, but also for implementation at clients’ offices.

Thematic maps as well as satellite image maps are still the most important medium for presenting and disseminating spatially referenced information. Digital cartography and Geographic Information System (GIS) techniques are the most efficient tools available for map production. Professional map layout is guaranteed by GAF's qualified cartographers. An advanced computing environment and state-of-the-art software allow GAF to integrate GIS and digital cartography techniques efficiently. GAF offers the entire scope of output products ranging from low-cost paper plots and high-quality printed & coated color maps to digital map files and fully-fledged web mapping services.

Digital Elevation Models and 3D Features for Digital City Models can be extracted by GAF from a variety of remote sensing sources. 3D feature data and photo-realistic 3D visualisations of the terrain are of increasing importance to a variety of application fields, including tourism, media, defense and security, regional planning and telecommunication. For many years GAF has served these fields with stunning 3D views, customised animations and fully interactive 3D fly-throughs, by combining earth observation imagery, vector data and digital elevation models to create virtual environments. Based on the variety of sources available through GAF’s Geo-Data Store, photo-realistic 3D worlds can be created and enriched by high resolution imagery, building models, land use information and ancillary data also for rural areas and remote regions of our planet. A special focus of GAF’s 3D activities is dedicated to the use of Euromap’s access to the Indian IRS satellite fleet. IRS-P5 Cartosat-1 stereo data and IRS-P6 Ressourcesat-1 colour imagery can be combined to create cost-effective 3D worlds.