Welcome to GPSFileDepot!

Main Menu

Map overlay/draw order on GPSMAP

Started by iridium7777, April 07, 2020, 08:34:25 AM

Previous topic - Next topic


Hello all,

i've been reading a lot about draw order of maps, i downloaded a free tool that modifies the draw order (1-31) of maps and am still not getting a result that i want and i wonder if it's possible.

-i have some older Garmin TOPO 24K maps that don't have all some of the back roads that show up on Garmin 100K maps that are included with my 66i nor the roads that i'm able to get through

-what i would like to do is enable a "base" map for example something like the 100K or the OpenMaps to show the roads and then on top show the 24K TOPO map so i can have the topo overlay on the roads data.

- i've modified the 24K topo maps to have priority of 30 while all other maps are <20 in priority but anytime i select the 24K TOPO map and any other map, any other map essentially overshadows the 24K TOPO and i can't see it at all underneath the other map.

is there a solution that i can use to force the overlay besides spending another $200 to get the most recent 24K TOPO maps (need 2 regions as i live between two states that unfortunately fall in different regions)?

thanks in advance for your answer.


Enabling two topo maps at the same time will just be a big mess, no matter how you do it. You would need one map that only has roads, and another one with everything else to make that work. And it's just not practical to do that with Garmin products, you'd need to make your own maps.

But it sounds like, on a more basic level, your problem is that the draw order only determines how the maps stack. The topo maps have opaque backgrounds that will hide everything behind them. The map with the highest priority should not have a background object. That would let the other map show through.

You *might* be able to address that issue with a custom TYP file that makes the background object (0x4b IIRC) invisible. And you might also address the issue of duplicate objects that same way, by making everything but the roads invisible. This is beyond the scope of what I can explain here though.

Not sure why your 24k topo doesn't hide the other maps if it has a priority of 30. That is odd.


Hi Boyd,

thank you for the quick response.  are you familiar with the GMapTool?   that is what i'm using, i'm also editing properties of the maps right on the sd card inside of the GPS unit.  The tool is telling me the priorities got overwritten to what i wanted them to, but still, pretty much any other map that i have stomps over the 24K TOPO map even though it has priority of 31. 

I wonder if the tool somehow thinks it's writing the data but it's not actually writing that data and GPS doesn't see it?

i wasn't able to find another free tool that manipulated the priority of the maps and this was my quick try at doing that.  is there another tool that could be used?

also, from what you write, it seems like even if i did get it to work it might not work the way i want it to work without me actually getting knees deep into making custom maps?


Quote from: iridium7777 on April 07, 2020, 12:04:43 PMalso, from what you write, it seems like even if i did get it to work it might not work the way i want it to work without me actually getting knees deep into making custom maps?

IMO, that's the situation. If you're particular about your maps.... make your own. I started doing that in 2008. I used to be interested in modifying Garmin's maps, but don't do that anymore. You might want to learn a bit about TYP files, they allow you to change the appearance of everything on the map, and as I said, you could make features invisible that way. Then you could make a transparent overlay with the roads that you want.

Here's an old thread I started on changing the appearance of Garmin maps, some of it is no longer relevant and I'm not interested getting back into this. So, "it is what it is"  :)

The online TYP editor mentioned there no longer exists. IMO, this is the best editor today and it's free

To make your own transparent road overlay, you could just use openstreetmap data. There are also good tutorials for making maps on this site, but that gets complicated.


thank you very much for your answer, yes, i'm realizing that i'm about a decade too late to be getting into this "hobby" the way i want, i'm finding a lot of links from 2008 where the whole forum websites no longer exist, never mind the links referenced from specific subject that are now missing.

can i ask one last question, this statement to me seems like it would do the greatest good for me: To make your own transparent road overlay, you could just use openstreetmap data, because then i can load my 24K TOPO map with a latest road overlay and this will give me exactly what i want.

what would be the relevant tutorial to do *explicitly* this task, to just create an .img overlay?


There are free tools like mkgmap (which I have not used) or cgpsmapper (which is discontinued but still available at These are complicated solutions that have a pretty steep learning curve.

For simplicity, have a look at Mapwel. I bought a copy many years ago and haven't used it since. But I think you can download and use it for free, but need to purchase/register to send a map to your GPS. Evidently it can directly download OSM data. If so, you could just delete everything but the roads you want. And the advantage of Mapwell is that it's a one-stop solution, where most other workflows involve using multiple apps.


Sorry for being late to the party, but FWIW a few years ago I followed the tutorial, first to make a complete state map; ran into a few problems and then realized I could get what I wanted by making a trail overlay. I followed the tutorial again, leaving out a lot of steps and making a few adjustments to turn it into an overlay. Works well. The tutorial requires a real commitment but I learned a lot.