This app shows what altitude you are at (in meters). For most official maps it shows how much higher you are than the lowest point on that map. It may or may not work on non-official maps depending on how the map creator designed it. If they made a conscious effort to make sure that the low point on the map was at a z value of 0, this app should work the same way. Otherwise you can use it as a relative altimeter. Many thanks to @Neo who helped with hooking up the altitude stream to the display Extract the ZIP to BeamNG installation folder/ui/modules/apps, so that the SimpleDigAltimeter folder is in that directory.
Packaging is really easy. You place your files in this subfolder structure: "Documents/BeamNG.drive/mods/unpacked/{Your Mod Name here}/ui/modules/apps/{Your App Name here}" for example my Ui Test Mod: After you made everything correct you can pack your mod in game and upload it to the repo::
i just happened to be looking for an altimeter right now and im lucky i found one that's working recently