When You Update Garmin Maps

July 2008

by Jim Morrison

Periodically, Garmin releases updated maps for their GPS units. I have a 2820 and they just recently released
the 2009 update. Having the latest maps can be handy,especially if it adds your home street in it for the first
time, as the 2008 version did for me. But with the update comes a potential routing issue. Garmin's
mapping program, MapSource, may produce different routes for the same via points when you update your
maps. This article describes how to check them and adjust them to result in the same route as with the older

Routing in MapSource depends on a bunch of settings in the program, like Route Style, Vehicle, Try to Avoid,
Road Selection Slider, Calculation Style, and Driving Speeds. If you and your riding buddies want to get the
same route, you should synchronize these settings.

To verify that you get the same route with the new map, you need to go through each route and do the following.  I will call the route done with the older maps "Original".


O p e n t h e MapSource file with Original in it. Right click on Original and do a D u p l i c a t e Route. This will create an exact copy of Original but with a different name...we will call it 'Duplicate". Now, right click on Original and do a Recalculate Route. You may or may not end up with the same route as the Duplicate. Right click on Original and select Show Selected Route on Map. Left click on the Original to highlight that route in yellow on the map.

Now you need to see if the recal cu lat ion changed the route from the Duplicate. The Original should be in yellow and the Duplicate should be in purple on the map displayed. If you see any purple, then you need to alter the Original route to match exactly the Duplicate route. You alter the yellow route by having the Selection Tool selected (the white arrow in the top tool bar) and then left clicking on the part of the route you want to change. When you do this, it will draw a line from the 2 via points on either side of the click. Drag this to the purple route and left click again to modify the route. You may have to zoom in and go over the entire route to be sure that both have routed the same.

When you have the Original matching the Duplicate route, you have it! Delete the Duplicate and move on to the next route. This sounds like a lot more trouble that it really is. It goes very fast once you get the hang of it. And if you really want to be sure that the route is perfect, you will need to zoom in on every via and waypoint to verify that it is still on a road. The map updates do place some roads in slightly different positions, causing the points to no longer be on a road. You can drag and drop them back onto the road. Another annoyance of updating the maps is that it clears any personalized Route Avoids you entered into MapSource. These too will have to be recreated.