Route problems

[+frefel]

garmin etrex vista c, openstreetmaps, google maps

 

I have had this GPSr for more than a few years and and finally am getting around to learning about some of it's amazing capabilities.

What I am exploring is the auto routing function and combining that with Google Maps. So I sucessfully obtain a GPX file that contains the map and driving direction using GMapToGPX. I load it into the Vista and view the receiver's map and all looks perfect; the roads and the route line. I review in Route the individual waypoints comprising the route and eacn is correct with the proper turn instructions exactly as given by Google Maps. Now the problem:

 

If I follow the route "Off Road" I am led from WP to WP in straight segments having nothing to do with the actual road (as expected) and the instructions are simply the bearings from one to another - not those from Google Maps. Not very high tech!

 

If I follow the route by "Follow Road" the unit immediately goes into "calculating" mode, sets up a route that is different from google Maps (and incorrect) and creates turn instructions that are completely unusable.

 

So my question is why is the unit messing up the perfectly good Google Map route by it's calculations and is there a way to circumvent that step (if I cancel it it says 'ready to navigate" but there is no route on the map and there seems to be no way to start it up)? Bottom line; I am getting all the necessary data into the GPSr but it then messes with it.

Edited July 25, 2011 by frefel

[+PokerLuck]

I'm not sure how helpful this is, but I have a similar problem with my Oregon.

 

I think the issue is that google maps and garmin use different algorithms for calculating routes, and the garmin one isn't optimized as well as the google one. Basically, we're asking an offroad GPS to operate as well as a Nuvi for calculating routes. Here's what I do to solve the problem:

 

In Basecamp or directly on the Oregon, I add waypoints to the route that force it to go the way I want it to go. Yeah, it's a pain, but it usually doesn't take too many extra waypoints to get it to work. On my Oregon, I can add intersections, places of interest, etc, but it's usually a lot more reliable to define a waypoint and tell it to use that. Just last night I planned a route from Knoxville, Tennessee to Wauseon, Ohio (MWGB), and I only had to add a couple of waypoints to make it go the way I want.

 

Also, due to personal preference, I sometimes want to take a route that's not very optimum, except by my standards. For example, I'd rather be going 60 miles an hour in the wrong direction than sitting still going in the right direction. I'll do just about anything to avoid traffic congestion. I can't expect a commercial product to know my preferences, so I just put up with having to add my own waypoints.

[+frefel]

Thanks for your comments PokerLuck.

Your idea that the algorithms are most likely different makes sense. Why would they be the same since Garmin and Google are competitors in some ways? Nevertheless I was hoping that someone had found a "workaround" to make the wonderful Google Maps data play well with my Garmin device. Your adding WPs is a good suggestion but it would be ideal to not have to do any custom manual additions.

 

A related question then is why does the GPSr unit have to "calculate" the Route transferred from even MapSource? Why can't the Route be compiled entirely on the desktop, if desired, and then uploaded to the unit without further massaging (assuming the same settings and maps in both)?

Seems like an easy and useful option to me but then I am not a programmer.