Feature request: DWELL option for geofence enter/exit detection

[XanderD99]

Problem
Fence enter/exit detection is instantaneous per SET. Objects reporting at high frequency (1 Hz GPS, ±5–15 m noise) near a fence boundary oscillate across it, producing rapid alternating enter/exit notifications. Every downstream consumer has to build its own debouncer, re-tracking state Tile38 already holds.
Proposal
Optional DWELL clause on fences — the edge event fires only after the condition has held for a duration:
SETCHAN warehouse WITHIN fleet FENCE DETECT enter,exit DWELL 10s OBJECT {...}

Object crosses in → pending; enter fires once it has stayed inside for the dwell. Leaves earlier → discarded, nothing fires. Symmetric for exit.
Only affects edge detections (enter/exit/cross); inside/outside unchanged.
Could be evaluated lazily on the object's next SET (fire when now - pending_since >= dwell), so no server-side timers.

Alternative considered
Client-side debouncing — works, but duplicates per-object/per-fence containment state server-side already has, in every hook/channel consumer.

[tidwall]

For high DOP situations, where the original GPS accuracy oscillates a great deal, you will see enter/exit jitters near fence boundaries.

What's been suggested to users is to use boundary buffers on fences. Basically setting up two geofences, where the primary handles the 'enter' and the buffer handles the 'exit'. Then the buffer will always contain the primary and be large enough to account for the GPS accuracy fluctuations.

A new geofencing engine is in the works for Tile38 2.0 (slated for this fall), and will include built-in fence buffering.

That said, your 'DWELL' idea is interesting too. I'll have to think a bit more on it, though it seems worth a discussion.

[XanderD99]

For single fences using that boundary buffer for exists is indeed a good solution.

However I forgot a part in my feature request. Where this could really shine could be in a new kind of FENCE DETECT where we could say track all fences in a collection or even further track on a full grid system instead of single indeces. (eg. FENCE DETECT GRID A5 ) Here a DWELL could be usefull for when the position is near an edge.

But since you mentioned a v2 engine is in the works this may be better to postpone until then :)