Questions about the XT, unpaved, routing, and map

[Peobody]

My wife and I just returned from a 3 day getaway to northern Georgia. While there, I used my XT for the first as tool to search for a POI and then let it get me to it. I have the unpaved avoidance enabled but twice it routed me on unpaved roads. Could this be explained by the fact that there weren't any paved roads to the POI? If so, should I have received a notice advising that the route contained unpaved roads?

While thinking about this behavior I wondered whether it was due to paved/unpaved errors in the map. As I watched the map I noticed that unpaved side streets were colored brown or black. A significantly more unpaved ones were brown, and I never saw paved on colored brown so does brown=unpaved? If so, there were a lot of paved/unpaved errors in the area we were in.

[danham]

As I plan day rides out of Killington, VT for an upcoming July trip, I find that looking at the Garmin map in Basecamp, zoomed in, is a reliable way of detecting dirt. To be fair, I have not checked the same roads on the XT, but am confident that a larger screen helps a lot, right down to showing exactly where a paved road turns to dirt.

I realize your issue was "in the field," so BC was not an option, but mention this in case it helps with troubleshooting the errors you found or future trip planning.

Here's an example:

Screenshot 2025-06-15 at 11.05.28 AM.png (256.79 KiB) Viewed 1025 times

-dan

[Peobody]

You're right Dan. I look at that, as well as using Google Maps, whenever there is a question of unpaved or paved during route planning. I just fired up Basecamp and looked at one of the unpaved roads that I was routed on (Bear Gap Rd in the images).. Basecamp shows it as paved which confirms a map error. Surprisingly, the smaller Low Gap Rd is paved. I remain curious whether brown roads on the XT indicate inpaved.

BC Bear Gap Low Gap rds.png (283.95 KiB) Viewed 1020 times

Street View Bear Gap Low Gap rds.png (2.52 MiB) Viewed 1020 times

[lkraus]

Colors are determined by the map data. I can distinguish between paved/unpaved roads easier with the thin brown lines of this Open Street Map:

41226.png (217.85 KiB) Viewed 1016 times

Though any map can have errors. This OSM map shows Bear Gap Rd as unpaved (and misnamed?) west of the Low Gap intersection, though the Google Street view shows that it is paved:

82470.png (238.36 KiB) Viewed 1016 times

[Peobody]

I just spent a good bit of time comparing brown road on the XT with what Google Maps showed. All are unpaved, but so are many that are shown as light gray on the XT. What I am realizing is that when using the XT to manually navigate, there isn't any way to know that an intended upcoming turn could be onto an unpaved road. I still haven't figured out what the brown road color indicates. FWIW, my map detail is set to Normal and map theme is "Garmin".

[BMurray99]

@Peobody I believe the brown color is indicating an unpaved road.

I live in the United States (Georgia), but have been using a customized UK map theme on My Zumo XT to display the map. I edited my map theme file to widen the brown lines that are displayed for unpaved roads.

I have also experienced the mapping errors you encountered. I have encountered unpaved roads that do not display as unpaved on the GPS. I have also encountered Basecamp calculating routes using unpaved roads, even though I have Avoid Unpaved Roads checked as an avoidance. It is pretty clear that Basecamp's roads surface data is not entirely accurate. Incidentally, I have set the avoidance for Unpaved Roads in Basecamp and my Zumo XT, but Basecamp still creates routes that try to use unpaved roads.

The problem has become so annoying for me where I live (rural mid Georgia) that I have started creating a custom map overlay that displays the unpaved roads that I know about as colored (brown, I think) tracks. I create the map overlay using the TrickTracks.org website. Some of these unpaved roads I have "discovered" while others I find as I scout potential routes using Google Earth and Google Streetview.

[Peobody]

The problem has become so annoying for me where I live (rural mid Georgia) that I have started creating a custom map overlay that displays the unpaved roads that I know about as colored (brown, I think) tracks. I create the map overlay using the TrickTracks.org website. Some of these unpaved roads I have "discovered" while others I find as I scout potential routes using Google Earth and Google Streetview.

When route planning, I also use Google satellite and street views to help identify unpaved roads. My problem was with using the XT by itself to get me to a destination. It isn't only the fact that it routed my on unpaved roads but also the sheer number of unpaved roads that I passed that could not be identified as such on the XT map (gray in color, same width as paved roads).

[jfheath]

Just a thought - I don't know.

The map theme files - eg something.kmtf (I think)

These Contain the colour codes, and width definitions for many things - routes and tracks

I wonder if selecting a different theme would show things better ? Or an edited existing theme file. Hint - copy an existing theme and edit the copy.
Better - make 10 copies, give them different names ( near the top of the file) and make each one test different things. It makes sense to name the kmtf file the same as the theme name declared in the file.

It is then easy to select 10 themes one after the other on the XT. it saves a lot of plugging, unplugging and waiting to re-start, and is much easier to compare the differences.

But if maps are wrong, there isn't much you can do.

[Grabcon]

I really like discussions like this. It brings back memories as to when I was in the GIS industry building digital maps. At the end of the day not all maps are created equal. Where and how the data is sourced, scrubbed, validated, etc has a tremendous impact on how we can use the base map data. When we speak of routing the same holds true not all routing algorithms are created equal. Plus the routing algorithms require the map data.

As an example I just created 3 routes that are within a half mile of my home. I used Google map, Basecamp and Furkot which uses OSM. Since I cannot see the underlying attributes of the street level data I can only visualize what I see on the screen. Both Furkot OSM and google showed a particular road graphically, Basecamp did not show the road. I know that no road exists, although the satellite imagery does show a dirt path. When I built a route using all three it was a two point method. Start point and end point. Basecamp and Google maps made the same route, while Furkot OSM routed down the road that does not exist. As a reference I went to the county GIS property site and it showed no platted road, but like the others the satellite imagery did show a dirt path. I expected this as I believe that they all use the same satellite imagery.

So as I have explained here if the data source for the maps and the routing algorithms aren't the same you can expect different results depending on what you use. Because of how my wife and I travel, long multi day trips I find that using Furkot is my best alternative. It allows be to easily break the trips up in to days and miles per day, helps with lodging and fuel. Is it perfect Hell no. But for the last 10 or so years whatever I use I have used Google Maps as the reference and I will adjust my planned route in Furkot accordingly. I do export all of my routes to my XT using the Garmin GPX export in Furkot. I then import all routes and view in the XT. Everyone is different base on their personal preference and location but this workflow works good for me. Oh and then there is one last item. All of this falls apart sometimes base on what the XT does to the GPX file. Again map data and routing algorithms.

PS: Furkot will export directly to Google maps which also helps valid the planned route.