Just so folks are aware, some amateur radio balloons have been using WSPR in conjunction with APRS in order to track global flights. For example, W7QO has used WSPR transmitters on solar powered floater flights at about 13000 meters/40000 ft. The data are collected using the global WSPR network, and then an APRS posit is created to make the balloon's position available.
If you look at https://tracker.habhub.org at the present time, you can see one W7QO's balloons (the HIRFW-6 flight presently near the Mediterranean Sea) that use use this WSPR/APRS combination. The balloon is transmitting WSPR on 20 meters, and you can see it on the WSPR map, although the WSPR call changes (I believe it depends on position). HIRFW-5 is another such flight that is currently aloft.
Todd AL0I