HerdTag

How the tag decides.

All the fence logic runs on the tag itself. Numbers here come from our simulator and are estimates until we measure real hardware.

A warning zone inside the line

GPS on a cow is usually off by a couple of meters. So the tag keeps a 20 m warning zone just inside the boundary.

  • Walking toward the line: a short cue.
  • Turning away: quiet.
  • Already out: quiet, and an alert to you.
A pasture with a shaded warning zone inside the boundary. A cow walking toward the line gets a cue. A cow turning away gets none. A cow outside gets none, and the farmer gets an alert. Boundary Warning zone, 20 m Inside: slow GPS checks Heading out Cue Turning back Quiet Out Quiet + alert
The cue depends on which way she's walking.

GPS checks speed up near the line

GPS uses the most battery, so the tag checks only as often as it needs to.

Where she isNext check
Deep in the pastureUp to 5 minutes
Within 50 m of the lineUp to 30 seconds
In the zone, heading out5 seconds
In the zone, not heading out15 seconds
Outside1 minute
GPS unsure30 seconds, no cues

Limits on the cue

  • Each cue is about 2 seconds.
  • No more than 10 per approach. If she keeps going, the tag stops and reports it.
  • No more than 40 an hour.
  • It never gets louder.
  • No cue when GPS isn't sure where she is.

A check-in is 11 bytes

Tags reach the barn gateway by long-range radio. Each check-in fits in 11 bytes.

Latitude Longitude Battery Status Fence number

Battery life

A safer fence means more GPS checks and a shorter battery. Try the tradeoff. These are model estimates, without solar.

Assumes a 300 mAh battery, 3 s and 25 mW per GPS fix, 96 check-ins and 20 cues a day.

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days on one charge
–
GPS fixes a day
Where the power goes

GPS is most of it, mostly on cattle standing near the line. Solar should cover a lot. We'll measure how much.