Tuesday, January 18, 2011
Occasionally people ask if they can use some of their existing map data in an Android GPS app like BackCountry Navigator.
I am pleased to announce that there is software that allows you to convert a GeoTiff, or a number of other calibrated formats, to a mobile atlas that can be used by BackCountry Navigator.
Take a look at MAPC2MAPC. This comes from a talented developer in the UK.
There is also a nice tutorial here on using it for BackCountry Navigator. As one correction to the tutorial, I would copy the files to the destination *before* choosing the mobile atlas. By the time you read this, that may already be corrected:
Calibrated map images often are from existing collections that people have bought, or data posted on government websites.
The geotiff format, for example, consists of a .tif image file with a .tfw (world) file for calibration.
Be patient when converting calibrated images – it may take longer than you think. There is lot of CPU and memory needed to reproject images and break them up into small pieces.
Some will ask why an Android GPS App can't just use geotiffs directly. The limitations of mobile devices will generally preclude this. It is common for geotiffs, for example, to be available at a size of 8192×8192. Try opening this size image on your Android device using the Gallery, or another image editing app of your choice, and it will probably choke. This is why Android mapping apps, including Google Maps and BackCountry Navigator, use maps in small pieces called tiles.
Others may ask if there is a way to convert a specific type of file. In some cases, this is not possible because the data is in a proprietary format that hasn't been well documented. This is usually data that people have purchased on CD-ROM, but occasionally, government data also comes in some of these closed formats. I don't know why the US Government would provide publicly owned data in formats that benefit commercial entities, such as .BSB and GeoPDF, but they do.
If you have a question about formats or another question about MAPC2MAPC, be sure and ask the developer, who is very responsive and helpful.