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.
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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
Landsat 8 scene (Band 5) topographically corrected
Gif animation: Landsat 8 scene (Band 5) before and after topographical correction
On the uncorrected scene the mountains are clearly visible by the shadows they cast because the sun was not in zenith during the capture of the image. Using the SRTM 1arc DEM makes it possible to model the illumination of the earths surface at the moment of the image capturing. Having this model, it is possible to correct the topographic shadow effect on the image.
The illumination model can be created as follows:
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November 17th, 2014
Join the Conference on Free and Open Source Solutions for GIS in Bangkok from 2nd – 5th of December 2014!
Februar 27th, 2013
A global online platform on large scale investments into land was released recently on www.landobservatory.org. Any user logged on to the system can provide spatial and context information on land deals. The idea behind landobservatory.org is to complement governmental information on land deals with crowd-sourced data that comes from the users and by that strongly improving the data availability- and quality on land deals.
landobservatory.org is currently being developed and coordinated by the Center for Development and Environment (CDE), University of Bern and the International Land Coalition (ILC).
– video-clip from ILC
– release information on Land Matrix
– informations on project from CDE
– demo of the platform with sample-data in Cambodia
März 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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Oktober 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)
Juni 25th, 2011
Socio-Economic geodata of the Lao PDR is now for the first time online available through the DECIDE info platform. The user can access the data either through map-viewing tools (MapViewer), or directly access the database with an online-gis application (DECIDE GIS).
März 5th, 2011
Satellites everyone knows. From hearsay. But what do these devices actually do, constantly circling the Earth 24 hours a day? In most cases, they are directed towards the earth, in rare cases, they „look“ in the other direction, into empty space. Satellites, which are directed to the earth may have many different functions. One important group are the so-called environmental satellites, whose purpose is the monitoring of the atmosphere and the earth’s surface.
At the time of Gauss, you went out into the countryside to produce topographic maps. These are still an important foundation for today’s surveying. However, even such detail-made maps have the property to become obsolete very quickly. Who has not held a newly bought map in his hands and noted with indignation: „The new ring road is not even on it!“.
Our Earth’s surface is constantly changing. And today even more than before. Man-made movements on the earth’s surface that currently take place, probably have never happened before. It is known that these changes have consequences that could be of explosive significance for mankind (see IPCC 2007). This is just one of several reasons why it is increasingly important to understand what is happening right now with our earth. And here, images from environmental satellites play a central role: permanently new pictures of a changing Earth’s surface.
Dezember 2nd, 2010
What do Geographers and Ivory have in common? What is a geodetic doing with an elephant-tooth? An item gains geographical significance at the moment, when its location becomes its distinguishing criterion. „Location“ means in the geographical sense a coordinate, thus a mathematically definable point somewhere on our earth. Does ivory have a coordinate? And: why and for whom could the „location“ of ivory become of interest?
read more: ivory and elephant protection
November 8th, 2010
The increasing integration of environmental issues into economic decision-making requires improved methods for the effective capture and visualization of complex relationships. Geographic Information Systems (GIS) offer the possibility to bring confusing decision-making processes into an organized network. This „modern cartography“ can serve as a basis for both the operative business as well as for long-term strategies.