Sometimes you want to rescale a raster layer, e.g., to reduce the number of categories, or to create a common scale for different raster layers. Very basic of course, so you can expect to find an appropriate function in any self-respecting GIS software. Just be aware that different terms are being used for the same thing, e.g., scale in gdal, rescale in GRASS and normalize in SAGA GIS. Below a few ways to do this using my favourite GIS programs: GRASS GIS, QGIS, SAGA GIS or gdal. Continue reading
Are you one of those people eagerly waiting for all those new features in QGIS that have been mentioned in the last couple of months on various forums and blogs? Well, the waiting is (almost) over. QGIS 2.2 is already available in OSgeo4W, Fedora, and Debian, while binary packages are being updated and will be available any time (or might already be available by the time your read this) on qgis.org. Continue reading
Google earth cannot be installed on Ubuntu 64-bit systems anymore. It requires the ia32-libs which is unfortunately deprecated in Ubuntu 13.10. Luckily I found a solution by mc4man on the Ubuntu Forums. For my own, and perhaps your convenience, I am repeating the instructions here. Continue reading
Last time I opened QGIS there was a notification that there was a new plugin; the auto-trace plugin. I just tried it out to see what it is all about. I must say, it is a pretty nifty tool. It let’s you digitize new features based on other features by tracing existing features. Continue reading
I recently found the interesting USGS map of global ecosystems. The data can be viewed online but can also be downloaded as geotif files, which is great as about every GIS program on the planet can read that format. Unfortunately the color legend is included as a *.lyr file, which can only be used in ArcGIS.
But the good people of USGS also provide a dbf file with, amongst others, the mapping unit, names of the ecosystem units and a color code. In ArcGIS this table can be linked to the raster layers, a features which is not (yet) implemented in QGIS. However, it is easy enough to create a color map from this file, which you can use in QGIS. It is just a text file. Continue reading
And it is looking great. I have been using the master (development) version for some time now, so I can tell you out of experience that this release rocks! Some of my favourites are the greatly improved map composer, great new styling features, integration of Sextante in QGIS core and much improved stability. For a list of major changes and new functions, go here. But, of course, don’t take my word for it, but check it out yourself and get a copy from the QGIS website. Continue reading
GRASS GIS 6.4.3 released – Birthday release for 30 years of GRASS GIS on http://grass.osgeo.org
One of my favourite raster formats to share is the geotiff, mostly because I always thought it is one of the most portable formats. But yesterday I got an email from a colleague that the geotiffs I shared looked strange in ArcMap, with hardly any values to show and an apparent range of values of 1,79769e+308 to 2,22507e-308.
The GRASS GIS development team keeps on introducing new features and enhancements to GRASS 7.0. One of the latest examples is the enhancement of the round() function in r.mapcalc. Previously this function would always returns an integer, regardless of its argument types. And because integers are always 32-bit, the result was limited to the range ± 2147483647 (2^31-1).
These limitations have been removed in the latest update of grass 7.0 (trunk r56313). Now the output type of round() is the same as the input type. Rounding to a given number of decimal places is supported with round(x, y) where y = number of decimal places.
In addition, the new function round(x, y) supports a negative number of decimal places: for example, round(119, -1) results in 120, and round(119, -2) results in 100.
Again great work by the GRASS development team!
Rounding a double precision raster layers (twi_900mm) to two decimals places (test).