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Globe-based earth browsers like GoogleEarth have turned web-based cartography into a widely accepted commodity. This success is based on the three components: The browser software itself, remote sensing data as a backdrop maps and thematic content layers. From a GRASS GIS perspective, the ability to communicate thematic content via earth browsers is a strategic means to quickly communicate findings to very large communities. This poster describes the current options to compose such thematic content layers by using GRASS GIS: Loosely coupled Keyhole Markup Language (KML) export functionalities provide the „glue“ for the seamless integration between the GIS and the earth browser.
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Advanced KML with GRASS GIS
Peter Löwe
RapidEye AG, Molkenmarkt 30, D 14476 Brandenburg a. d. Havel, Germany, Contact: [email protected]
References:
r.out.kml: http://grass.osgeo.org/wiki/GRASS_AddOns#r.out.kml
v.out.ogr: http://grass.fbk.eu/grass64/manuals/html64_user/v.out.ogr.html
v.out.kml: http://grass.osgeo.org/wiki/GRASS_AddOnsvr.out.kml
RapidEye Maps: http://www.rapideye.de/home/news/news-extra-page.html
Motivation
Globe-based earth browsers like GoogleEarth have turned web-based cartography into a widely accepted commodity. This success is based on the three components: The browser software itself, remote sensing data as a backdrop maps and thematic content layers. From a GRASS GIS perspective, the ability to communicate thematic content via earth browsers is a strategic means to quickly communicate findings to very large communities.
This poster describes the current options to compose such thematic content layers by using GRASS GIS: Loosely coupled Keyhole Markup Language (KML) export functionalities provide the „glue“ for the seamless integration between the GIS and the earth browser.
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).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 standalone workflows. This approach enables automated spatial data processing, effectively shielding the user from the GIS processing details, while providing KML-based results for interactive examination.
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.
Viewshed Analysis Demonstration Two alternative sites for digital broadcast stations towers qre assessed through polygon overlays (Odenwald Region, Germany).
Red: Spatial coverage from proposed primary site, Green (translucent): coverage from alternative site. Green (opaque): Special interest region.
Source: P.Löwe 2010
Satellite Image Map DemonstrationCombined usage of of point, polygon and raster layers in a KMZ created from an automated script:RapidEye satellite maps of the eastern Mississippi Delta in RGB (left) and CIR (NIR-RedEdge-R, right), including imagery metadata.
Source: RapidEye, 2010
GRASS-based KML Workflows Green: GRASS modulesRed: Advanced KML generation including layout.Grey: Standard KML generation.Blue: Manually edited KML derivate from standard workflow
