[talk-ph] Car navigation using Garmin with OSM

riber101-osm at yahoo.com riber101-osm at yahoo.com
Sat Jan 9 08:27:52 GMT 2010


I have now been using OSM to navigate around Metro Manila and a trip to Mindoro and have some experience to share:

On several occasions Garmin tried to guide me through on way streets going counter flow

The OSM maps keeps getting better and each time I find a missing oneway info I just add it when I get home, so next time I will get the proper routing. So that should take care of that problem.

Some roads are not connected as having separate ending points

Guess this is due to the editors we use that doesn't warn about this.

When funny routings occur I make a note and correct the issue when I get back to the computer.

So time will solve this as well.

Garmin routing times are overly optimistic as typical speed in Manila is 15 km/h and 20-40 km/h on SLEX
Garmin often routes through narrow streets rather that using dedicated through fares

The main reason Garmin is unable to provide better routing is the lack of maxspeed info for most roads.

I suggest to add the maxspeed info for all roads according to the traffic code RA4136 as follows:

SPEED LIMIT Passengers
Cars and Motorcycle Motor trucks and buses 
Open country roads, with no "blinds corners" not closely bordered by habitations. 80 km. per hour 50 km. per hour 
"Through streets" or boulevards, clear of traffic, with no " blind corners," when so designated. 40 km. per hour 30 km. per hour 
City and municipal streets, with light traffic, when not designated "through streets". 30 km. per hour 30 km. per hour 
Through crowded streets, approaching intersections at "blind corners," passing school zones, passing other vehicles which are stationery, or for similar dangerous circumstances. 20 km. per hour 20 km. per hour  
Garmin is able to use the maxspeed info to calculate the fastest route and by this automatically select roads with the higher speed limits.

So I will advocate that maxspeed is added to all roads in the Philippines. Until this happens Garmin will keep preferring roads WITHOUT speed limits as is thinks they are the fastest.

Happy mapping
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