Is there any way a simple North-South sighting line could be etched on the top of the Tempest unit so it could be properly sighted? I used a screw driver, sitting it on top of the unit and aligning it with the indicator arrow on the side of the unit. I then sighted down the shaft of the screw driver to get a somewhat accurate fix. As a rated Navigator in the USAF, degrees matter.
Here’s another helpful tip. Tempest already has the “North Marker” (Blue arrow). What I did was to label “S” on the opposite side of the marker. Also labeled “S” on the pole mount. “S” faces South and the blue marker on the opposite side faces True North. (There will be a Sonic Transducer for each of the four directions: N E S W)
Since an app on a mobile device is needed to setup the Tempest, that device most likely has access to the internet, too. Just open the map app, make sure it is displaying the satellite view with true North ser at the top, slide the map until the Tempest mounting point is on one edge or the other of the screen and then look for a land mark to use to aim the Tempest. It takes less than 30 seconds to do this and once it is set, you won’t need to mess with it. I’ve used this on multiple occasions when I go camping and take my mobile station with me. It is fast, accurate, and simple and does not require anything added to the Tempest system.
a gyroscoop measures relative rotation, not absolute orientation. An electronic compass might work, but it is pure overkill for an easy, one time setup (and it would only work in combination with a gps (inside tempest or using the one on your phone)
Many phone do have a compass app showing true north and magnetic north. You would need the true north.