Garmin Topo 24k maps vs GPSFileDepot state Topo maps

[rudysdad21]

What is the difference between the Garmin Topo 24k maps on Micro/sd and the state Topo maps on this website?  Are the state Topo maps 24k also?

[Boyd]

There really isn't an answer to this question because there's no such thing as "GPSFileDepot maps". GPSFileDepot is just an archive of maps that are made by many different people with different skill levels and interests. So you will see a big variation in the maps on this site.

But you could made some generalizations...

Garmin's 24k topo maps include DEM (Digital Elevation Model) data in their proprietary format that provides 3d shaded terrain. This feature is only available on Garmin products, there are no third party tools for using DEM in a map.

Garmin's 24k maps contain routable roads based on the same data from HERE that is used in their City Navigator products. This means they can provide turn by turn routing instructions to reach a destination. Almost none of the maps at GPSFileDepot are capable of this, they cannot calculate routes.

Garmin's maps also contain a rich database of POI's - things like gas stations, restaurants, stores, etc. Maps on this site are not going to have that level of detail.

Garmin's maps can work seamlessly with each other across state lines. In most cases, maps from different authors at GPSFileDepot will have some issues where they meet.

Garmin will offer tech support for their maps and will "hold your hand" if you have problems installing or using the map. This could be an advantage for people who are not technically inclined.

Garmin's maps are copy protected which severely restricts their use. The downloadable Garmin topo maps can only be used on the original GPS for which they were purchased. So if you sell or lose your GPS, your map will be useless. The maps that Garmin sells on SD cards can be used in any GPS but you must use them on the original SD card, they will not work if copied to another card.

[popej]

Garmin's 24k topo maps include DEM (Digital Elevation Model) data in their proprietary format that provides 3d shaded terrain. This feature is only available on Garmin products, there are no third party tools for using DEM in a map.

This is no longer true, mkgmap and BuildDEMFile can create DEM now. See:
https://github.com/FSofTlpz/Garmin-DEM-Build
http://www.mkgmap.org.uk/websvn/revision.php?repname=mkgmap&rev=4093

[Boyd]

Wow, so somebody finally cracked Garmin's DEM format? That must be pretty new, I followed this for years and progress was very slow. Regardless, I don't think there are any maps on this site that use Garmin compatible DEM (unless perhaps your own? )

I'm not going to plow through all the files at those links - what is the bottom line? Is it possible to take DEM in one of the standard formats and insert it into a map with mkgmap?

[popej]

It is very new, one can expect some problems, but it works. I have published maps of Africa and South America with DEM. They become big.

BuildDEMFile creates subfile DEM based on given area or area extracted from subfile TRE (subfile as an internal part of an img tile). It is quite tricky to add DEM to existing map, but can be done with gmaptool.

Mkgmap is is easy. Just put some option like required resolution and path to SRTM files. Then mkgmap adds DEM to each tile. Actually I haven't tried with *.mp source, but with OSM data, maps compile without problems.

[Boyd]

Cool - thanks for the info! 

[rstilt]

Actually, speaking from personal experience, the Garmin 24K maps have lots of errors when their birdseye imagery is overlayed vs the topo maps that are found here on GPSfiledepot.com. I have included a couple of screenshots to illustrate this point. I am using the 100K from Garmin because my 24K data was accidentally destroyed, but the alignment issue was the same on both Garmin versions. However, I have not found any errors on maps downloaded from here. The sample I took was random,  but the errors from Garmin can be found on pretty much every square inch of their maps, they are terrible in my opinion.

[jolly47roger]

I suspect Garmin get roads etc from USGS. I have been working with USGS data and there are several errors - the worst was a road running through the middle of a lake!

[Boyd]

I'm a little surprised by this claim about the 24k topo maps. I have the Garmin Northeast 24k Topo and it looks good. No need to guess where the data comes from, all you need to do is look at the product page. The road data is routable and comes from HERE (formerly Navteq), which is the same company that provides roads for Garmin's City Navigator maps. https://buy.garmin.com/en-US/US/p/27612

The main dig against the Garmin 24k Topos is that they don't contain enough unpaved roads and trails. Now the old 100k Garmin topo maps were another story, I have owned about three different versions of those over the years and the roads originally came from the US Census Bureau TIGER line files. This was the original source for OpenStreetMap data as well, and was also the recommended source for mapmakers at GPSFileDepot.

They improved a bit over time, but were never very accurate. The old TIGER files had huge errors, but their origiinal purpose was as a reference for census takers, not the creation of digital maps for navigation.

My understanding is that Garmin switched to HERE for the 100k maps a couple years ago also and that it was a big improvement. But my days of buying Garmin maps are long gone.