eTrex SE and custom map

[Sibstr]

So I already have an eTrex SE
I tested all possible variants and found that the GMAPBMAP.IMG file must definitely contain a map with the map ID "CITIES".
The CITIES map may contain:
Codes: 0x0100, 0x0200, 0x0300, 0x0400, 0x0500, 0x0600, 0x0700, 0x0800, 0x0900, 0x0a00, 0x0b00
Kind: Point
Category: Cities
The problem is that the standard map ID can contain only numbers and HEX codes and all sw checks this and won't allow letters to be used. Unfortunately, the "system" map from Garmin uses the letters in the map ID, in our case CITIES. I would need someone with high level knowledge of IMG files to help solve this problem.
Data from the second file F0071BLA.IMG eTrex SE cannot displayed. Maybe we'll see it in some future firmware, but that's just speculation. From my point of view, it makes no sense to deal with this.
I still see the CITIES mod as realistic. It would be good if each country could make its own CITIES.IMG file with all cities and villages, not just a few of the biggest cities.
In my opinion, the biggest shortcoming of the eTrex SE is the lack of POI support.

[readysteadygo]

Did you try the ASCII coding for the map ID?
CITIES = 43 49 54 49 45 53 = 434954494553
F0071BLA = 46 30 30 37 31 42 4C 41 = 4630303731424C41

Not sure if you can add so many characters / such a big number.
Can even add a different one to try out. If it works, you can add custom layers to the map
OTHER = 4F 54 48 45 52 = 4F54484552
It's possible that the SW automatically converts from HEX to ASCII and shows text version of map ID, but when packing/creating a new map it expects "raw" HEX name.
Also possible that the GPS unit (eTrex SE) has a white-list of map IDs, and will not show any random name, just the ones in the list. So "OTHER" or "JOHN" will be ignored.

Worth a try, IMHO

[Jakobw]

No it doesn't work with ASCI, I used a hex editor to changed all the ID(which is encoded as ASCI in the Binary "soup") occurences, but it still doesn't work, also does the format of the map look a bit different.

[Sibstr]

I managed to edit the GMAPBMAP.img file from the eTrex SE!

Required SW:
* GPSMapEdit
* cGPSmapper
* GMapTool
* HxD (Hex Editor)

The Process:
I took the original GMAPBMAP.img file and used GMapTool to split it into two map files: 22906436.img (CITIES) and 22906439.img (F0071BLA). I opened the 22906436.img (CITIES) file in GPSMapEdit and imported my own POI database (in my case, a list of all 6,259 cities and municipalities in the Czech Republic). Subsequently, using GPSMapEdit and cGPSmapper, I compiled a new 22906436.img file. Then, I reassembled the files back together in GMapTool and adjusted the file header to this state:

Header: dd.mm.yyyy hh:mm:ss, DSKIMG, XOR 00, V 3.00, Ms 0, 006-F0071-00
Mapset: GMAPBMAP.img

Map size s-f CP prio PID FID Name
22906436 MPC 810172 3 1252 25 T 0 0 CITIES
F0071BLA MPC 77792 4 1252 0 T 0 0 Worldwide NR Small Basemap

Next, it was necessary to change the map ID from 22906436 to CITIES. No free map software is capable of doing this. This is where HxD comes in. Using a "hard" edit, I had to overwrite all occurrences of "22906436" with "CITIES". Note that it is crucial to maintain the 8-character length, so for "CITIES," you must add two spaces in hex code (20 20). The result looks like this:

Map velikost s-f CP prio PID FID Name
CITIES MPC 810172 3 1252 25 T 0 0 CITIES
F0071BLA MPC 77792 4 1252 0 T 0 0 Worldwide NR Small Basemap

This works, and the eTrex SE is able to display these points on the map!
I also tried adding other map elements to F0071BLA, but the eTrex SE was unable to display any of them.
The Conclusion:
We are able to add points/POIs to the map, but map elements like roads, contour lines, or rivers... not yet. At least not for now.