1. Geospatial tools & technologies used
The open source geospatial technologies and tools are used for automatic satellite data download from FTP, data conversion, re-projection, publishing of raw data as web map service and development of web based information system for visualization of raw data in spatial domain. GDAL(Geospatial data abstraction layer), an open-source tool/library has been programmed using C#(programming language) in .net environment for satellite image file type conversion (like .img, .jpg into .tiff) and for re-projecting satellite images into standard format(like LCC into WGS 84). Standard GDAL utilities ‘gdal_translate’ and ‘gdalwrap’ have been customized for file type conversion and re-projection. Once the re-projection is completed, there is a need to generate the service of the satellite images. Geoserver (http://geoserver.org/) working on Open Geospatial Consortium (OGC) standards have been programmed using REST API's (Application programmable interface) to generate automatic web map services (WMS) of the satellite data sets. To implement this cURL, an open-source command line utility has been programmed using php server side scripting in web environment. To view the published satellite data (WMS), a spatial 2D GIS viewer integrated with query builder is developed using OpenLayer 2 API's. Basic GIS functionalities like zoom-in, zoom-out, pan, identification, mapping distance and calculating measurement are integrated in the spatial viewer.
Standard image processing tools like Erdas Imagine Georeferencing modules for image geo-referencing and ArcGIS functionalities for spatial analysis have been used in the software developed. 'Autosync' functionality of Erdas imagine has been used for rectifying the geo-referenced images using C# in .net environment, whereas standard ArcGIS functionalities are programmed in arcpy for flood delineation, damage statistics generation and map generation. Detail methodology will be discussed in the workflow section.
2. Methodology
Figure 1 Methodology
3. Pre processed dataset integrated in 2D spatial viewer
Once the satellite data is available for processing from the FTP, a console C# .net script(using GDAL API's) takes the dataset as an input and unzipped it followed by re-projecting the dataset into WGS-84 latitude longitude projection system. The re-projected standardized dataset is organized into file based system with a metadata entry in database which further can be used for scene retrieval and KMZ generation. The script also generates a KMZ of the dataset and again zipped it, for publishing the data set as web map service. It do so to fasten the process of image uploading to Geoserver for WMS generation. cURL script with php uploads the satellite datasets and publish the uploaded data as a WMS. The WMS layer gets automatically integrated into open source map viewer with metadata and path of the physical data set as shown in figure 1.
Figure 2 : Pre processed dataset integrated in 2D spatial viewer