readsb omits lat/lon for a contact heard without a current position; about a
third of every /v2/mil response is such rows. They made every military
snapshot partial, so a contact that left the feed was retained at full
opacity for five minutes instead of fading and leaving on the missed-poll
limits. A row with a hex and no lat/lon now leaves the snapshot complete and
is listed in retainIds, as OpenSky's null-position rows already are.
Aditya
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