Advanced KML with GRASS GIS
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The document discusses advanced KML functionalities in GRASS GIS, emphasizing viewshed analysis and the integration of thematic content layers for effective web-based cartography using earth browsers like Google Earth. It highlights challenges in color-scheme export from GRASS GIS and introduces enhanced KML export modules to improve data visualization. Additionally, it mentions ongoing developments in KML standards to optimize access to large datasets.
Advanced KML with GRASS GIS
- 1. Advanced KML with GRASS GIS Peter Löwe RapidEye AG, Molkenmarkt 30, D 14476 Brandenburg a. d. Havel, Germany, Contact: loewe@rapideye.de Motivation Viewshed Analysis Demonstration Globe-based earth browsers like GoogleEarth have turned web-based cartography into a widely accepted Two alternative sites for digital commodity. This success is based on the three components: The browser software itself, remote sensing broadcast stations towers qre data as a backdrop maps and thematic content layers. assessed through polygon overlays (Odenwald Region, Germany). From a GRASS GIS perspective, the ability to communicate thematic content via earth browsers is a Red: Spatial coverage from strategic means to quickly communicate findings to very large communities. proposed primary site, Green (translucent): coverage from This poster describes the current options to compose such thematic content layers by using GRASS GIS: alternative site. Loosely coupled Keyhole Markup Language (KML) export functionalities provide the „glue“ for the seamless Green (opaque): Special interest integration between the GIS and the earth browser. region. Source: P.Löwe 2010 GRASS-based KML Workflows Satellite Image Map Demonstration Green: GRASS modules Combined usage of of point, polygon and raster Red: Advanced KML layers in a KMZ created from an automated script: generation including layout. RapidEye satellite maps of the eastern Mississippi Grey: Standard KML Delta in RGB (left) and CIR (NIR-RedEdge-R, generation. right), including imagery metadata. Blue: Manually edited KML derivate from standard Source: RapidEye, 2010 workflow Approach GRASS GIS provides built-in support for KML export in a minimalistic way (v.out.ogr): Only vector data can be exported in default coloring scheme.This results in a de-facto media break, since color-schemes can not be easily sent to the globe browser from the GRASS session and would require manual editing. To mitigate this situation, two add-on GRASS modules were created to provide enhanced support of vector export including cartographic information (v.out.kml, Peter Löwe, 2007) and also raster map export (r.out.kml, Hamish Bowman, 2008). References: The current functionality includes raster-map export and the control of line width, opacity, coloring and custom icons for vectors via general settings and attributes. It is highly effective in scripted GRASS-based r.out.kml: http://grass.osgeo.org/wiki/GRASS_AddOns#r.out.kml standalone workflows. This approach enables automated spatial data processing, effectively shielding the v.out.ogr: http://grass.fbk.eu/grass64/manuals/html64_user/v.out.ogr.html user from the GIS processing details, while providing KML-based results for interactive examination. v.out.kml: http://grass.osgeo.org/wiki/GRASS_AddOnsvr.out.kml With the ongoing development of the KML standard, the scripts continue to evolve to provide more options. Support for timestamps and optimized access for large datasets is under development. RapidEye Maps: http://www.rapideye.de/home/news/news-extra-page.html