Category Archives: Data handling

Import MODIS data in GRASS using r.in.gdal

NASA offers access to its MODIS and ASTER data sets through Reverb|Echo. The data comes in HDF format and uses the Sinusoidal grid tiling system. If your gdal is compiled with HDF4 support (use ./configure –with-hdf4), you can use gdal, … Continue reading

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Extracting lines ending with specific character using sed or grep

A quick note (to myself mostly) about how to extract lines from a text file that end with a specific set of characters. In Linux, you can very easily do this using ‘grep’ or ‘sed’. But, first a little bit … Continue reading

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Multivariate Environmental Similarity Surfaces (MESS) index in GRASS GIS

The Multivariate Environmental Similarity Surfaces (MESS) is an index that represents how similar a point in space is to a reference set of points, with respect to a set of predictor variables (Elith et al 2010). The function was first … Continue reading

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Opening MODIS tiles in QGIS

NASA offers a very convenient web-based tool to select and download the tiles you need; Reverb / ECHO.  The tiles are in HDF format and use the Sinusoidal grid tiling system (proj4 definition: +proj=sinu +lon_0=0 +x_0=0 +y_0=0 +a=6371007.181 +b=6371007.181 +units=m … Continue reading

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Publishing your Freeplane mindmap on the web

Freeplane is a great mind mapping software. I use it e.g., to jot down and organize notes from articles I am reading, creating lists of software, relevant websites, etc. One of the advantages of Freeplane is that you can export … Continue reading

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Using TileMill to create maps in mbtiles format

The development of open source spatial tools is amazing. A while ago I wrote how one could create mobile maps using a range of tools, including GRASS or QGIS, Maptiler, and Mobile Atlas Creator (MOBAC). If you are using an … Continue reading

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From xy table to spatial table in spatialite

A short note on how to create a spatial table from a table with latitude and longitude coordinates in your SQLite / Spatialite database. In the example below, the table I am working with is ‘labels’.

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From multiple rasters to one Google earth layer

To create a Google earth map, I would normally export my raster layers as a geo-referenced png file and subsequently use maptiler (or gdal2tiles.py) to create the Google earth map (see here for more details). Because I want to create … Continue reading

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Cross tables in R, some ways to do it faster

In R to create a contingency table of the counts of the combination of two variables, I would normally resort to table(). But how fast is it? A question that becomes more relevant when working on large tables and when … Continue reading

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From attribute table to QGIS style file – step 1

I have a large number of GRASS vector layers with in the attribute table a RGB column defining the colours of the corresponding mapping units. Unfortunately, unlike GRASS, QGIS does not offer the option to to set colours from an … Continue reading

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