Monday, October 29, 2012

Openstreetmap Zoom

I have played around with this before. Having recently set up Mapnik again to render Openstreetmap data. Currently it is using the standard Openstreetmap osm.xml file so should look like the mad used on the main website.

This animation is created by rendering each frame with Mapnik. The script is based on a hack of the standard script that comes with Mapnik. It simply loops, and for each loop a new bounds is calculated to provide the zoom effect.

A seperate script is used that adds the watermarks in the bottom corners of each frame. This was done with the help of ImageMagick. Finally, avconv was used to convert the frames into an mp4 file.

The next step is to make an animation based on a GPX file. That will take a GPX file as input and provide a zooming animation that shows the start, and an overview of the whole GPX track.

Wednesday, October 10, 2012

Garmin Vista HCx

Some time ago, I purchased a Garmin etrex Vista HCx. Certainly not the most sophisticated GPS system available, but still good fun. It works well in the car, the pocket and on the bike. The only real downside was that the maps that come with it are fairly limited, and it would work out expensive to purchase all the maps I may want to use with it.

That said, it still works very well for recording tracks. When I first had the device, Openstreetmap was still fairly incomplete in my area, so it was good fun uploading GPX traces to help add detail to the map.

Eventually, I found out how to create a map from the Openstreetmap data that can be loaded into the Garmin etrex Vista HCX device. It requires a number of steps, but these are easy in Linux.

Grab the data

The data that is used to build the Openstreetmap map is freely available. There are a number sources for the data, but it would not be normal to want the entire world database. The people at Geofabrik provide a usefull service where they maintain a selection of extracts. Please remember this is provided as a service, so be kind to their servers. The extract I get is the one for Great Britain.


Get the tools

A number of tools are required to process the data to make it useful for the Garmin. Following is a list of tools that I have found work for me.

Used to split the map into manageable pieces.
Converts the OSM data into format suitable for Garmin device

Use the tools

These tools can be used as follows. This is not a definitive guide. Best refer to the relevant sites for the tools, but this is how I am using the commands.


java -Xmx1536m -jar splitter.jar \
   --max-nodes=1000000 \
   --mapid=63240001 \

This will generate a series of files from the input.


CMD="java -Xmx1024m -jar mkgmap.jar \
   --route --remove-short-arcs \
   --add-pois-to-areas --index \
   --location-autofill=bounds \
for f in 6324*.osm.pbf
    echo $f
    $CMD $f

After this is run, we should have a number of .img files. At this point, it may be possible to use these tiles with the Garmin map tool for the PC. But why bother. Let us just bundle these all up into one large file.

java -Xmx1024m -jar mkgmap.jar \
   --gmapsupp --family-id=50 --product-id=1 63*.img

This should result in a single map file named gmapsupp.img. All we need to do now is copy this to the Garmin directory on the SD card used by the Etrex Vista HCx.