Archive for the ‘News’ Category

OSM printed: Open Street Map on paper in Chiang Mai

Saturday, April 16th, 2016

For the first time, a printed version of Open Street Maps is now available in Chiang Mai. The map is a cycling map, it highlights roads that are especially suitable for cycling and proposes small routes (based on the class:bicycle key).

The map is printed on A2 (420x594mm) and, with a scale of 1:25,000, covers a good area of around 9 x 13 km around Chiang Mai City.

OSM Chiang Mai

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Topographic correction of Landsat imagery using GRASS GIS

Wednesday, April 22nd, 2015

The GRASS module i.topo.corr to correct topographic effects on imagery works quite impressively on the Landsat imagery using the recently released Enhanced Shuttle Land Elevation Data with a 1 arc / 30 meter spatial resolution. Here is a quick example to show the difference of the original image and the corrected image that was processed using i.topo.corr and the enhanced SRTM elevation model in GRASS GIS:

Landsat 8 scene (Band 5) uncorrected

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FOSS4G-Asia 2-5 December 2014

Monday, November 17th, 2014

Join the Conference on Free and Open Source Solutions for GIS in Bangkok from 2nd – 5th of December 2014!

foss4g-asia

Forest Fragmentation index using GRASS GIS

Sunday, March 11th, 2012

Forest fragmentation index map

Worldwide, forests have been changed dramatically by humans, particularly during the last decades. The loss of old forest stands causes threads to biodiversity and life-important ecosystem services. Loss of forests does not necessarily mean a total clearing, but it starts with ‘forest degradation’, which is in many cases caused by fragmentation processes.

In order to measure the degree of global forest fragmentation, an approach was developed by Riitters et al. (2000). This approach can easily be implemented on any scale using a selection of tools provided by GRASS GIS, one of the most powerful Open Source GIS platforms. To perform a complete forest fragmentation calculation in one step, these tools were put together into one shell-script, that you can download from the GRASS-addons page: r.forestfrag.sh.

Update: Thanks to Ecostudies, the script was further developed and can now also be used in GRASS 7.

 

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Ortho-rectification of QuickBird imagery with OSSIM (Open Source Software Image Map)

Sunday, October 16th, 2011

QuickBird imagery is increasingly used in different areas of land-related planning activities. However, by delivery the images are normally not ortho-rectified which means that, due to distortions, they cannot be used for mapping or spatial analysis, particularly if the image area covers mountaneous terrain.
Ortho-rectification is supposed to correct for the image distortions that are caused mainly by hilly terrain, but also by systemic deviations that occur during image-capturing at the sensor.
This tutorial leads through the ortho-rectification of QuickBird Standard ortho-ready satellite imagery, using an Open Source approach with OSSIM.

download tutorial > qb_ortho_ossim_2011 (500kb)