Category Archives: online mapping

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 a map based on several layers, I can not simply export a raster layer. Instead, I need to create a map in QGIS map composer and georeference that map, following the steps described here.

Unfortunately, as it turns out there are limits in the size of the map you can create in QGIS map composer. Perhaps there is a way to increase this, but I am not sure how. An alternative solution is to smaller create sub-sets of the map. But how to get them together as one Google earth map again? Continue reading

Visualizing confidence in data on map: example of SoilWeb Mobile

See this post for a nice example how one can display the level of confidence in the data presented for a mapping unit on a map. The SoilWeb provides the distance from the nearest map unit polygon boundary. It gives the user a little more information that can be used to judge a relative degree of confidence in the returned soils data; Continue reading

Looking for historical maps of the Netherlands

History, nature and land use changes, it all comes together in ‘Verborgen wildernis’ (Hidden Wildernes) by Kester Freriks. It is a book describes about twenty five former ‘wildernesses’ in the Netherlands, in their current and historical context and based on and illustrated by historical maps. These include maps from the ‘De Atlas der Neederlanden‘ (atlas of the Netherlands), part of the special collections of the University of Amsterdam). It gives a good idea of what [wilderness] has been lost, but also what can still be found, if only one wants to find it. See this website for an interview with the author (in Dutch).

Reading the book I became curious about what historical maps of the Netherlands would be available online. Continue reading

MapTiler to create online maps II

In an earlier post I wrote how I created a mash-up map with MapTiler. There is an option in MapTiler to set transparency for a color, but this didn’t work for me at the time. I therefore created a small script to convert the background color to transparent and to process all PNG tiles generated by MapTiler using the PNGNQ utility.

I am working on a new online map and this time setting the background color to transparent in MapTiler works like a charm Continue reading

Nice step by step tutorial how to create an Open Source Web Map

Ever wanted to create an open source web map but not sure where to start? The short tutorial ‘Blueprint for Creating an Open Source Web Map‘ by Michelle Ballinger might be just what you are looking for. This tutorial “takes the user through the steps of creating new data, modifying existing data to the map’s specifications, creating style layer descriptors, writing basic HTML, and posting to the Internet”. These steps are done in respectively QGIS, UDig, any text editor and GeoServer. Continue reading

MapTiler to create online maps

For a project a few years ago we created a vegetation map for central and southwest Kenya (see http://ecodiv.org/trapnell for more information). The map together with documentation was initially made available on CD-ROM. I also created an online map. Apart from the version mentioned in this post, I also created a version with MapTiler.

MapTiler requires a georeferences image file as input. To export the vegetation map from my GRASS GIS database to a georeferenced image, I used the r.out.tiff function.

r.out.tiff -t input=veg_ethiopia_pnv@vegetation output=vegethiopia.tif

The resulting file can be used in MapTiler to create map mashups for Google Earth, Google Maps or OpenLayer. MapTiler offers a wizard like interface which leads you step by step through the process. Continue reading

TACCIMO – a template for Assessing Climate Change Impacts

Collecting and producing data is one thing, combining it and making it easily accessible and useful for the end-users another.

The Template for Assessing Climate Change Impacts and Management Options (TACCIMO) is a nice example of a Web-based tool that provides land owners, managers, and planners in the United States with the most current climate change science available. Continue reading

A vegetation map in OpenLayers

For a project a few years ago we created a vegetation map for central and southwest Kenya (see http://ecodiv.org/trapnell for more information). The map together with documentation was made available on CD-ROM. However, we wanted to publish the map online too. The original maps were in svg format, and turned out to be too slow for online publishing. Moreover, they could not be combined easily with other maps.

A widely used and open source option for online publishing of maps is OpenLayers. This is a JavaScript library for displaying and building rich web-based geographic applications, similar to what is offered by e.g., Google Maps and MSN Virtual Earth. An important difference though is that OpenLayers is open source software. It furthermore is easy to create dynamic maps on your website with your own data and with direct access to many different maps, including Google, Yahoo, Bing, OpenStreetMap and other datalayers.

As a pilot I have created an OpenLayer map with the vegetation map. Continue reading

ClickFu in QGIS

Although Google maps and other online mapping tools become more powerful, creating and analyzing maps is still typically done using a desktop GIS. I am for example using GRASS GIS and QGIS for my work. These are very powerful tools, but what if I want to get a more detailed overview of how a certain area looks like? Or if I want to find out the towns in a certain region, or verify the existence of a lake in another? Continue reading