A geofence is a virtual perimeter drawn on a map around a physical work site — store, office, factory, customer location. Modern attendance and field apps use geofences to ensure that an employee's punch happens at the right place, not at home, not in the parking lot, not at a competitor's office. This is what turns mobile attendance from "phone tap" into "verified work-site attendance".
How geofences work
Most geofences are circular — a centre coordinate plus a radius (typically 50–200 metres depending on site size and GPS accuracy). Polygonal fences are available for irregular sites (long warehouses, multi-building campuses). When an employee's device GPS reads a location inside the perimeter, the app fires an event — auto check-in, attendance acceptance, visit-form prompt — and a corresponding exit event when they leave.
For attendance, the geofence acts as a gate: a selfie taken inside the fence is accepted; a selfie taken outside is flagged or rejected (configurable). For field workforce visits, geofence entry auto-checks the rep into the customer site and starts visit dwell time.
Perimeter design — getting the radius right
Three rules. (1) Match the radius to GPS accuracy. Typical outdoor accuracy is 5–30 m; indoor accuracy degrades to 50–100 m on the device, sometimes worse in deep buildings. A radius smaller than the worst-case accuracy will produce false rejections. (2) Include the staff entrance, not just the centre. Most punches happen at the door; if the fence centre is on the far side of the building, accuracy can drift the punch outside. (3) Avoid overlap. If two sites are within 200 m, distinct geofences need careful centres and radii to avoid cross-site false positives.
Edge cases — buildings, basements, multi-floor
GPS accuracy collapses indoors. For sites where staff spend the work day deep in a building, the punch should happen at entry — the geofence catches them at the door, the app accepts, and the rest of the day's data does not depend on GPS. Some apps additionally use Wi-Fi SSID anchors or BLE beacons for indoor verification.
For basements and multi-floor offices, the punch ideally happens at the lobby (good GPS) before staff descend to a low-signal area.
Multi-site rollout
For 1–5 sites, draw fences manually on the map — 5 minutes per site. For 10–100 sites, bulk-upload a CSV with site name + centre coordinates + radius — minutes for the entire set. Per-branch managers see only their own site; owners see all. Geofence breaches (off-fence punches) are flagged automatically in the daily report.
Audit trail — what payroll needs
Every punch record carries: timestamp, device ID, IP address, GPS coordinates, accuracy radius, distance from geofence centre, in-fence / out-of-fence flag, anti-spoof signals (mock-location, rooted, emulator), and the selfie image with liveness verdict. This is the audit pack your payroll team needs when staff dispute a deduction or when a labour-law audit asks for evidence.
Geofence + anti-spoof, together
Geofence enforcement on its own is gameable — a rep using a fake-GPS app can fake a position inside the fence. That is why geofence is paired with anti-spoof detection (mock-location flag, rooted-device, physics checks) to make the combined surface defensible. Either signal alone is necessary but not sufficient; together they produce the audit quality of fingerprint hardware at one percent of the cost.
Put this into production today
WappBlaster Attendance Suite ships everything described in this guide — selfie + GPS attendance, anti-spoof, geofence, multi-shift, payroll, leave, expense and reports — on published tiers (attendance from ₹2,100/year (7 staff), tiered adds for larger office headcount; field users priced separately), with free onboarding and a 3-day trial that needs no credit card. See the full product or start the free trial.
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