Digital Geography

Create A Raster Layer Index With QGIS And GDAL

When working with raster datasets, it is hard to keep an overview of the raster files in use and their coverage. Most raster data providers may keep metadata in the filename itself, like path, row and a timestamp. But for more convenience, it is possible to create an index of your raster maps. This article will show you, how to accomplish this in QGIS or with the Terminal.

regular spaced points… interpolation madness…

The geodata department of the city of Berlin offers a great portfolio of free geodata for everyone to use. One dataset is the result of some LIDAR measurements and is offered as a txt with x,y and d values. This is commonly known as xyz data but should not be mistaken as a simple whatever-delimited text file. This dataset is regular spaced and therefore can be threatened easily with QGIS. But let me first show you some interpolation results which can be produced as well. Interpolational madness If you want to create raster data from a point shapefile or a…

reproject and filetype change in python/pyqgis for QGIS plugin

In my current work on the qgis2leaf plugin I had the idea to place raster data on a leaflet map as an image overlay. With this in mind and looking at a webmap I needed to consider a good filesize, a strict projection of EPSG:4326 and a strict filetype as well. So decision was: projecting everythin to EPSG:4326 and changing file type to *.jpg. I know, how to do this in the Terminal and in QGIS. But what options do you have using python/ pyqgis only? Terminal For doing this work in the terminal/shell/command line the one and only choice…

short announcement: TopoToolbox 2: Geomorphometry made easy in MATLAB

< p align=”justify”>Digital elevation models (DEMs) exist today for the entire globe with consistent quality. Improvements in sensors and data processing give a clue that in the future elevation data will be available in even better spatial resolution and accuracy. Discovering the richness of information inherent in DEMs should thus be supported by good software. Here, I want to give a brief account of TopoToolbox 2, the second version of a MATLAB toolbox for exploring and analyzing DEMs. Dirk Scherler from Caltech and I have been working on many changes to the previous version to make TopoToolbox faster, more memory…

OpenSource QGIS + PostGIS installation: “the Windows way”

A short time ago I’ve posted an article on the installation of QGIS in combination with a PostGIS database in the background. As we all know, Windows is mostly used as OS on a PC so this is the Windowized version. This is a short summary that sums up the article of a site called Boston GIS. I’ll show you how to install QGIS version 1.8 (which will be updated in some days) and PostgreSQL with PostGIS extension and show you the first steps in the import of shapefiles and raster data.

Free Sources of Geospatial Raster Data

I’m always looking for good sources of free data, so I thought I would post a few here in case they were useful to others. The sources listed below tend to be larger providers of regional to global level data, however, please post suggestions in the comments if there are other sources you like and think should be added. I had initially planned to include vector data here, but I think that will be another post as this one got quite long. SAR Data Free Synthetic Aperture Radar data can be some of the hardest to find, but it is…

Map Projections, spatialreference.org and gdalwarp

Map Projections The question of map projections and how to reproject data is one that comes up often in discussions with both experienced colleagues and those new to the geospatial profession. I’m not going to go through a complete discussion of map projections here, as there are many resources available on the Internet that can help you. I’m going to focus more on how to move data between projections. At its most simple a map projection is simply a mathematical description of how to take data on the surface of a sphere, that are inherently 3-dimensional, and transform them to…

QGIS Plugins – Point Sampling Tool

Previous posts in this series QGIS Plugin – RasterCalc QGIS Plugin – OpenLayers Point Sampling Tool I have recently been working on a project that has required the extraction of information from a raster layer based on point positions in a vector layer. I’m not a big user of vector data, but I suspect this problem comes up from time to time. In my investigation of how to solve this, I found a great QGIS plugin, the Point Sampling Tool. The Point Sampling Tool allows you to easily extract values from a raster layer based on a vector point layer.…

The End of the Landsat 5 Era

If you have been working in the space remote sensing community for any length of time you have almost certainly crossed paths with Landsat 5. After 29 years of watching Earth, the U.S. Geological Survey announced that Landsat 5 would be retired slowly over the coming months. Of course most people are looking forward to Landsat 8 (LDCM), but it is worth it to look back for a bit on Landsat 5, this stalwart icon of Earth remote sensing. More information from the USGS can be found at the official release As always, thanks for reading.

QGIS Plugins — OpenLayers

Click for previous article in this series about RasterCalc How often have you been working on a project in QGIS and wanted some nice background imagery, perhaps for a quick and dirty evaluation of your own data? I find I need this with growing frequency and a great way to do it is through the OpenLayers plugin for QGIS. Of course, if you know of a good WMS for your area of interest you can always go that route, but the OpenLayers plugin is a great addition to your QGIS toolbox. The OpenLayers plugin is available through the official QGIS…

Favorite QGIS Plugins – RasterCalc

RasterCalc QGIS Plug-in QGIS is an open-source geographic information system that is familiar to many geospatial professionals. I find more and more that I’m able to use QGIS for most of my GIS needs and this is in large part due to the great plug-ins that are available. In this post I want to give an overview of one of my favorite plug-ins, RasterCalc. If you have QGIS installed on your system, you can download RasterCalc from the official plug-in repository, here. After downloading, you can install it in the appropriate location for your system. In my case that is:…