Exporting rasters to Mbtiles using GDAL

Web maps are generally made up of many small, square images called tiles, which are placed side by side in order to create the illusion of a very large seamless image [for a good explanation, see here].

Tiled based maps can be made up of many tiles. Loading all those tiles would be inefficient and slow. That is where the MBtiles, developed by Mapbox, come in. The MBtiles specification is an efficient format for storing millions of tiles in a single SQLite database.

I have written before about Tilemill, a great tool to create great looking interactive maps. Since then more tools have come available to create MBtiles. Continue reading “Exporting rasters to Mbtiles using GDAL”

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 “Visualizing confidence in data on map: example of SoilWeb Mobile”

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 “MapTiler to create online maps II”

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

MapTiler to create online maps

For a project a few years ago we created a vegetation map for central and southwest Kenya (see here 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 “MapTiler to create online maps”

A vegetation map in OpenLayers

For a project a few years ago we created a vegetation map for central and southwest Kenya (see here 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 “A vegetation map in OpenLayers”

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 “ClickFu in QGIS”