Routing with the new Google Maps Data

I spent some time look around Google Maps since they stopped using Teleatlas in the United States this week.  Essentially I poked around looking for errors that are usually in the street vendor data.  Mostly these are minor errors such as a single line segment misspelled.   The problems usually appear to have originated with the original TIGER street data and never been repaired.

For the areas I’m familiar with the data looks good.  There has been lots of conjecture as to where all the data was sourced.  I suspect at least in Loudoun County where I live the source is the local government, that is unless the occasional segment errors were fixed by Google.  The one error I did find was an edge case within the routing.

White’s Ferry is a small ferry line just north of Leesburg, Virginia.  White’s Ferry is supposed to be the late cable operated ferry on the East Coast, for a little historic background and to see it in action Lonely Planet has a good video clip.  It is the fastest way across the Potomac to rural Maryland on the otherside.  When I lived in Leesburg I occasionally used it when traveling to suburban Maryland such as Rockville because it took the same amount of time and didn’t require any driving on the Beltway.  I’m fairly sure that previously if you routed it would take you across White’s Ferry.  I ran the route through a couple routing websites to compare results.

On Google it takes you up and around across a more northern bridge which is a much slower route in this situation.  Bing Maps routes through the ferry, as does MapQuest.  Yahoo goes up and around across the bridge the same way Google does.  Potentially Yahoo could be a routing engine problem because their tiles say they are sourcing NAVTEQ data and on NAVTEQ’s site you can successfully route from Leesburg to Martinsburg across the ferry (note:  I could not figure out an easy way to link directly to the NAVTEQ route here).

I checked other ferry lines and it appears Google can do the multi-modal routing, but the ferry information is just missing for White’s Ferry.  As an experiment I have reported the missing ferry and requested notification when it is fixed.  You can be sure that I’ll report back here when I get a response.

While performing this exercise I checked OpenStreetMap to make sure the ferry was already available on the map there.  Routing doesn’t work so well in the routing service I used it took an even longer route to go been Leesburg and Martinsburg. At least with YourNavigation.org you can export the route data to GPX and use it in whatever device you like.  If I’m going to use my local knowledge to repair map data I want it back to use however I like.  You can report bugs in the Google map data, but you can’t export it to GPX like you can with the OpenStreetMap data.

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October 8, 2009  Tags: , ,   Posted in: Map Commentary, OSM, routing

5 Responses

  1. Andrew Semprebon - October 8, 2009

    Apparently starting January, you’ll be able to enter those corrections yourself into http://www.google.com/mapmaker

  2. Scott Drennan - October 8, 2009

    It is possible to export Google map data to GPX, although not via a Google API. Josh Larios put together a bookmarklet and some hosted code which produces useful GPX files from google routes. I haven’t tried the OpenStreetMap GPX files, so can’t compare the two.
    http://www.elsewhere.org/journal/gmaptogpx/

  3. Kate Chapman - October 8, 2009

    Kind of a cool hack, but I’m not entirely sure that isn’t against the Google Maps terms of Service though.

  4. Joe Ganley - November 17, 2009

    The nav in my van doesn’t like White’s Ferry either, even if I tell it ferries are okay. It’s pretty funny to watch the estimate drop by about an hour when we land on the other side.

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