v1.6r1-eu025 with US settings

As the eu024 pre-release didn't show any new issues, this release now finalizes the pre-release.
In addition to the changes mentioned in the pre-release, the final release features a better OSM offline map for the web interface, as well as the option to download US Sectional charts or OpenFlightMap Data for the EU. Also, the Stratux files are now almost completely self-contained in /opt/stratux, instead of installed all over the place.

Quite a significant update with many under-the-hood improvements, but also quite a few bug fixes and some user facing changes.
Most notably, we are now using a 64 bit base operating system, which significantly improves quality of life for developers and reduces CPU usage of the PI.
This also means that there will be no .sh update file for this version. You will need to re-image your SD card to install this update.

If you are using a T-Beam with OGN Tracker, I strongly recommend updating the firmware as well, as there were compatibility improvements with PilotAware.

Changes
Important notes to EFB developers:
Due to a bug, bearingless targets had the tail number "Mode<0x14>S" instead of "Mode<0x20>S" (note that 0x14 = decimal 20, so the bug was using decimal 20 instead of hexadecimal 20). If your EFB was using the well known tail number "Mode S" to draw a bearingless target circle with GDL90, please update your code to not only identify "Mode<0x14>S", but also "Mode<0x20>S".
For GDL90, Stratux will now always report ellipsoid ownship altitude, as the spec. requires. This can not be changed in the web interface any more, as pretty much all EFBs seem to expect it like this by now.
Features
By default, Stratux will now write log files only to a temporary ram disk to safe your SD card in case of power loss. This can be changed from the web interface
Added option to set transmit power for OGN Tracker (T-Beam), including disabling transmission
Added support for MPU6500 AHRS chip as found on some recent GY-91 boards
The default low resolution OSM Offline world map is now a lot more detailed. It's still low-res, but much better than before
It is now possible to download additional offline map archives. Right now, this includes OpenFlightMaps (~700MB) for Europe and US VFR Sectional charts for the US (~5GB). See here for more details: https://github.com/b3nn0/stratux/wiki/Downloading-better-map-data
General improvements
Switched to new RaspiOS aarch64 base image
Switched to latest librtlsdr
Switched to go 1.16, with full usage of go modules to improve the build process
Some improvements to the web interface code and help texts
Disabled swap file to reduce SD card writes
Updated dump1090
Minor improvements to Stratux EU case: more venting holes, rounded corners, slightly larger screw holes
Ublox GPS LED PPS turned off to make it less distracting when night-flying
On the PI4, Wifi-Direct is now forced to the 2.4Ghz band, instead of using the 5Ghz band, which is not compatible with older devices
Direct browsers to a maximum cache timeout limit of 5 minutes, to reduce issues reported from not clearing browser cache after updates
ogn-rx-eu startup is now delayed until a valid GPS time is received, as it could otherwise crash from time to time when the system time suddenly changes significantly
Increased 868Mhz reception range by implementing error correction in ogn-rx
Stratux is now installed almost completely self-contained to /opt/stratux, instead of all over the system - excluding system configuration (Wifi hotspot, DHCP, ...)
The image doesn't ship with the source code any more. If you want to do development, you will have to clone it yourself
Bugfixes
Minor improvement to bearingless target selection to send to EFB
Fixed bearingless target name "Mode S" (see notes to EFB developers above)
Better handling of ICAO ID vs. non-ICAO ID for PilotAware targets
Fixed some aircraft type codes in Flarm-NMEA protocol (drone, ground object)
Fixed a potential crash if communication with your AHRS chip is unreliable
Fixed issue that it was impossible to set the "Baro altitude offset" back to 0 once it was changed
[OGN Tracker Firmware] Improved compatibility with original Pilot Aware
Known issues
The RaspiOS Kernel seems to log a lot of errors when using Wifi-Direct. This doesn't seem to cause any issues though. See here: raspberrypi/linux#4348
Due to the 64 bit requirement, this image will only run on the Pi 3B and newer. Older versions, or the Pi Zero are not supported and won't be supported in the future.
OpenFlightMaps offline data is missing France - it's not downloadable from their website.
PLEASE MAKE SURE TO CLEAR YOUR BROWSER CACHE AFTER INSTALLING THE NEW VERSION!