Digital Geography

DEM comparison: SRTM 3 vs. ASTER GDEM v2

Let’s get ready to rumble! No, just kidding. We are all excited about the recent message from the white house: SRTM “1” (1 equals 1 arcsecond, whereas 3 was indicating the 3 arcsecond a.k.a. 90m DEM) or the official title SRTM-2 will be available for free in the next months (orig. here, dg here). So why is it so important? Most DEM-interested people will answer: “Use the ASTER DEM if you need 30m!”. But let us have a closer look on both systems and how they perform.

Advanced access to free climate data for Germany of the Climate Data Center

Since July 1st 2014, the Deutscher Wetterdienst (DWD) eased restrictions for the usage of climate data and provides users with a big dataset of free climate data for Germany. You can obtain the data, using the FTP-Server of the Climate Data Center (CDC). The following data in the following resolutions and formats are ready to download for free: measured Paramater at the DWD-Stations for climate in hourly, daily, monthly and annual resolution and phenology in annual resolution as txt derived Paramater at the DWD-Stations for soils (pot. and actual evaporation, soil moisture, soil temperature, max. depth of frost penetration over…

short announcement: Berlin geodata downloadable…

I don’t know what’s wrong with the governmental insitutions in Germany/Berlin: They have this law, that all the geodata are somehow under an open license but to me it’s always a little hard to find it. Once you’re on the website you need to visit the site of Geodateninfrastruktur (GDI)->Geodienste to find sources for WFS, WMS or downloadable data: Once you find it, lots of data is waiting for you! you can get historical maps for Berlin, DOM and DEMs (in 2 and 5m ground resolution), soil key figures, ground water tables and other stuff. In the end you can… – easy editing polygon and polyline datasets for mapping purposes

Mapshaper by mbloch is one of my favourite “swiss army knife”-tools if you need fast data reduction and topology first aid in polygon data handling. There a two versions of mapshaper. The first is a hosted webservice:, where you can easily upload .shp-, GeoJson- or TopoJson-Files via drag&drop or folder selection. Afterwards you have to chose your simplification method (Douglas-Peucker, Visvalingam or modified Visvalingam) and some other options like “repair intersections”, “auto snap” and “prevent shape removal” and you’re ready to go.

Geoscience Australia – geodata collection via WMS, WFS and WCS

The Australian government now provides a bunch of commercial and free geodata on their Australia Geoscience-Portal. Like the well known U.S. data provider Earth-Explorer, you can do a product search, browse the full collection of data and application or find new released datasets. Besides this common features of data portals, the site offers a great collection of processed maps, datasets and really nice interactive models for geoscientific issues of Australia via WMS, WFS and WCS (Web Coverage Service).

Earth in near real time: new Earth monitoring approaches

Since the start of Google Earth in 2001 (it was re-released in 2005 after Google acquired it from Keyhole, Inc ) remote sensing images made their way into every day life. But if you are looking at the images they show on Google Earth or Google Maps: You will see historic data and it strongly depends on companies like Digital Globe, BlackBridge (a.k.a. RapidEye) or Astrium and the contracts with Google whether you will see new or old data.

Analog Geography – German soil of the year 2014 is the vineyard soil

Sometimes you need to replace bits and bytes with dirt and soils, and today’s news are really pushing me to leave the desk and to go for a walk. Every year, the Deutsche Bodenkundliche Gesellschaft (German Pedological Society) announces the Soil of the Year. Next year’s soil is the Vineyard Soil! It’s not only one, but a whole group of soils known for their high fertility and their anthropogenic, mineral rich R-horizons. In Germany, those R-horizons formed as early as in Roman times in some regions, since the Romans brought the civilization wine to Germany. Currently, I am feeling a…

georeferencing images in QGIS using OSM data: how to distort the City

You probably already referenced maps with written coordinates but using photos or images is a little different as you need some characteristic points so you can control the position of the image according to the real world. In this little tutorial I’ll show you how to do a so-called image to image refernciation using Open Streetmap data and QGIS 2.0.1 Dufour.

Data extraction and clean up with tabula and open refine

Everyone working with data knows the problem: You found some interesting data for your journalistic project or statistics for preparing a nice map, but the data comes messy and hidden in PDF-files, not automatically readable for your program. Normally you have to write out and clean up the data by hand. But there are tools for that…

OpenSource QGIS + PostGIS installation: “the Ubuntu way”

A lot of you out there are probably working on Windows Systems using ArcGIS and I have to admit that the possibilities with ArcINFO in the background and a proper GDB (GeoDataBase) are really big. But let’s be honest: A lot of your tasks are more or less everyday business, right?! So let us have a look on building a GIS workplace using QGIS 1.8 (which will be updated the big way in some days/weeks) and PostGIS which is a spatial enhancement of PostgreSQL.

short announcement: huge categorized list of geodata

Thanks to @seandebasti who enjoyed this year’s “Society of Cartographers Annual Conference” at Staffordshire University who send us a short link on Twitter. The link provides a huge list of 319 freely usable geodata catalogues. Robin who created this list put it on the table via linkedin first and was highly “liked” for this. He covers several topics: Elevation Weather and Climate Natural Disasters Land Cover/ Land Cover Ecology and many more … If you’re interested in his activities you may also want to check Robin’s blog. He blogs about GIS, Cartography and also tutorials with a wide view. You…

how to create clustered points in leaflet

The leaflet API is very simple and tries to deliver best performance and style for commonly used features like tilelayers, points and lines and markers in general. So when we would like to visualize points it is possible to have a very large numbers of points. So lets have a look on such an basic example. I’ve created a point shape file with QGIS which has approx. 1.000 points embedded. Let’s have a look on a normal webmap with this density of information: As you can see, we’ve inlcuded a second js file with the point information called points_rand.js. You…