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Mapsource Issue


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I just want to confirm my experience on Mapsource mileage accuracy. I have noticed that the mileage for a route in Mapsource versus actual miles is considerably off. Has anyone else experienced this?

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Afternoon frenchwv


There have been some complaints of this on other forums. The only time I have personally seen a mileage difference of more than couple of miles is when I mistakenly add in a waypoint or shaping point on the wrong side of the road or otherwise do something in MapSource that adds miles to route.



Go over each route in question at a very high resolution looking for switch backs, wrong side of freeways, and other routing errors. If possible do this with your actual traveled TRACK showing on the same map.


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How much is considerably off? Like D.R., my experience has been that's it's off but usually not by much more than a couple of miles.



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I mapped a route in Mapsource that was 1,134 miles and then after I did the exact route, it ended up being 1,033 miles. I have just mapped a route that is 1,688 miles in Mapsource and 1,564 miles for the same route in Mapquest. When I run the route this weekend, it will probably end up being somewhere in the middle.

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as noted above what is "off"

lets say the actual mileage comes in at 1,600. That means your mapsource route is 95% accurate. For me that is good enough for route planning. 88 miles over ~1,700 is not a concern. But I guess if your planning iron butt routes, or going for points etc. I can see were it could be a big issue at only 95% accuracy.


I will have to check mine, never have really noticed it before. Now you have me curious.

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Afternoon frenchwv



Upload both your tracks & the route directly from your GPS back into MapSource of that 1,134 route.


Then Zoom in to the 2 mile Zoom level and go over the route and tracks. See if you can find the issue.


Something has changed, -- either your GPS changed the route from what you originally made in MapSource or you actual tracks are slightly different than your routing import.


If all is EXACTLY the same ie. tracks EXACTLY mirror the route then MapSource has an error in some of the road or roads on it’s current mapping. (what NT map are you using?, is the map the same in the MapSource as in your GPS?)


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Thanks for the info. Yes, the mapset is exactly the same in both (NT 2011.4). I noticed the difference last week after riding in the Minuteman Rally. 95% is unnaceptable to me for rally route planning.

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Afternoon frenchwv


Another thought here--


What GPS are you using maybe that will point us somewhere.


If something like Zumo then delete the route in your GPS then re-import it from MapSource. Then see what the GPS shows for miles vs. what MapSource shows. Maybe your GPS is changing the route slightly as it re-calculates during import.



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There is of course, the possibility that your odometer isn't 100% accurate and the real mileage lies between that of Mapsource and that you record.

Just my 0.02.

I get differences between measured and computed, but haven't really given it much thought as makes no difference to my rides. (not iron butt, or measured for accuracy)

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It is almost certainly a difference in the calculated route. Try this - In Mapsource create the route, point to point using 'Fastest' as the routing option. When done, make a copy of the route (the 'duplicate' function. Change the default routing option to 'Shortest' and recalculate the duplicate route. Now you can view the differences pretty easily by noting the different colors of the two lines. Pick one of the routes and add/move waypoints until the Mapsource 'Fastest' and 'Shortest' routes are identical. Load this route into the GPS.


This extra step should eliminate any differences in the Mapsource and GPS route calculation engines. I do this when I'm creating a route for a group ride ... it rarely takes more than a couple of extra waypoints to make the two agree ... unless I-20 in Texas is on the route - but that's another story.

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Interesting. I knew i couldn't could on my BMW mileage counter, now i can't count on mapsource either. Wallace this does seem to be a serious issue considering you are trying to plan for the IB rally.



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First things first...


All the input other guys have made is absolutely right on.


But... lets get the basics right first.... If you load a route to the unit- it always recalculates the route.


The unit-calculation for various reasons may be slightly- or majorly different from what you planned.... not only in mileage but in actual route.


The first-order idea is to be certain that the route preferences used on the GPS are exactly the same as those set on Mapsource.

Same map edition... too.


If all that is true, then do as they say above, and also go to Zumoforums.com a great resource, even if you don't have a zumo- there is an entire forum section just on Mapsource.

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Morning Hopz


Slight hijack with possible added help on this thread-


Are you sure that all GPS units recalculate the route upon import? My 60CSX doesn’t appear to recalculate on import. In fact I can directly drag & drop a route into the unit with no further asking or appearance of re-calculating. In fact if I import a route that is from a mismatched map set I sometimes get routing that is not on the roads but along side them.



I know my Zumo re-calculates but it also has avoidances that it can impose on the route as it re-calculates.

This is easy to catch if the Zumo changes the route by re-importing it back into MapSource then comparing the original (re-named) route with the freshly imported route.


Ok, back to your normal programming.


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