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"GPS Streets"

With the announcement that Ordnance Survey have released OS Open Data (basically, most of their map data for free (as in speech and beer), I decided to see if I could supercharge my Magellan Explorist 210 with street level mapping.

Turns out to be non-trivial, especially on 64 bit Windows 7!

That said, I have managed it, and what I had to do was as follows:


  1. Obtain MobileMapper Office. You can download v3.40 from ftp.promagellangps.com, or version 2.70 if you search the net hard enough. The chief difference is apparently that 3.40 requires the GPS device to be plugged in.
  2. Install it, then tweak MMOffice.ini to add the line

    Byte_Order=1 in the [DEVICE_DEFAULTS] if you have an explorist.(refer to msh tools for more info).

  3. While you’re on msh_tools, download MMOCoverter
  4. Pop across to OS Open Data, and download Meridian 2 in ShapeFile format.
  5. While you’re waiting for the e-mail from the OS, download and install FW Tools – you’ll need it for a data transform later.

That’s the easy bit. You now have all the data and software required. The next bit is to transform the data to WGS84, import into MMO, export as a detailed map, convert to Explorist, and chuck onto the device.

I decided I wanted the entire set of roads in my GPS – you may decide otherwise.

  1. Extract the Meridian 2, and take a copy of

    • a_road_polyline
    • b_road_polyline
    • minor_rd_polyline
    • motorway_polyline

    In each case, you need all 5 files with the same base name.


  2. Fire up an FWTools command window, and run the following command for each of the 4 files you just copied:

    ogr2ogr -t_srs WGS84 wgs84 a_road_polyline.shp

    This says transform the source file (a_road_polyline) into WGS84, and save the new file into a folder call wgs84.

    This step is required because MMO doesn’t seem to handle British National Grid properly – I was getting errors of around 50 to 100m in my street locations when I did a straight import from the OS supply.

  3. Fire up MMO.

    1. Tools / Background maps
    2. Vector Maps
    3. Map Editor
    4. Layer / Add
    5. Choose one of the 4 road files.
    6. Double click on new layer to bring up the properties, and change the Display Attribute to be ROAD_NAME
    7. Fiddle with the scale if you want. I found that for minor roads an appropriate setting was 1:25k. On my device the colour, width, etc, don’t seem to make any difference, but it’s nice to do for display in MMO.
    8. OK
    9. Repeat from step (iv) for the other 3 files
    10. Save if you want to
    11. Operations / Create Map (and go and make a cuppa)
    12. Close the Map Editor window.
    13. Highlight the new map, and Attach Map
    14. OK
  4. You should now be able to see the full street set (you may have to zoom a long way in if you set a large scale).
  5. The whole road network is too large for my GPS, so I had select a region to export.

    1. Tools / Create Region
    2. Draw the rectangle of the subset of roads you wish to upload.
    3. Right click to make it stick
    4. File / Upload to GPS / Background Map
    5. Store on Hard Drive
    6. Finish (and make a cuppa)
  6. Now fire up MMOconverter.exe
  7. Input/output file on my machine is C:\Program Files (x86)\MobileMapper Office\Export\Images\NewMap.imi
  8. Plug in your Explorist, select USB transfer, and copy the file NewMap.imi into the “Detailed Maps” folder.
  9. Unplug the Explorist, go to Menu / Active Map / Detail Maps / Select Map and choose “NewMap”
  10. Enjoy!

All due credit to the OS for giving away their data, and also to msh-tools, without whom I wouldn’t have been able to even get started.

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