Geofenced attendance on construction sites: how it works and where it fails

A geofenced attendance app lets a worker punch in from a phone only when the phone’s location falls inside a boundary drawn around the site. It replaces the register that gets filled in at the end of the day, and it makes proxy attendance harder. It does not make it impossible, and it fails in predictable places. Knowing both sides is what makes a rollout work.

How it works

1. An admin draws the site boundary as a polygon on a map.
2. The worker opens the app and taps punch in. The phone reports a position and an estimated accuracy: a radius such as 12 m within which it thinks it is.
3. The system checks the position against the boundary, allowing for that accuracy, and records the time against the worker’s shift.
4. Usually a selfie is taken with the punch as a second check.

Drawing the boundary

• Draw what you mean by “at work”. Include the access road, the store yard or the labour camp only if a punch from there should count. A boundary that takes in the labour camp lets people punch in before they leave their room.
• Do not draw tighter than GPS can measure. If phones on your site are often off by 15 or 20 m, a boundary that hugs the plot line will reject people standing at the gate. Leave a margin, especially around the building itself.
• Check the map is current. Satellite images can be months or years old. Walk the boundary with a phone before you go live.
• Redraw when the site changes. A new block, a second gate or a casting yard across the road all need the boundary updated.
• Long, narrow work such as roads and pipelines fits one fixed polygon badly. Draw the boundary around the active stretch and move it as the work moves.

How accurate is phone GPS?

It depends on where the phone is.

• Open sky: a reasonably modern phone is usually accurate to within a few metres.
• Dense city streets and tall neighbouring buildings: signals bounce off walls and the position can drift by tens of metres.
• Basements, high-rise cores and deep inside a concrete frame: GPS may not work at all. The phone falls back on Wi-Fi and mobile towers, which can be off by hundreds of metres, and it reports a large accuracy radius to say so.
• Just after the phone was switched on or left in flight mode: the first fix can be slow and rough.

This is why a well-designed system allows for the accuracy the phone reports. If a worker’s position is 15 m outside the boundary but the phone says it is only accurate to 30 m, they may well be inside. Rejecting them punishes honest people working in the basement. The flip side is that a position with a very large accuracy radius proves little, so tell supervisors what to do then. Usually the answer is to step out into open sky and try again.

Be clear-eyed about one more thing: on some phones, location can be faked with mock-location apps. A geofence raises the effort needed to punch in from home. It is not proof, and spot checks still matter.

Selfie checks: presence is not identity

Two different things get called a face check.

• Face presence confirms that the photo contains a face. It stops a punch made with a photo of the ground or a helmet. It does not know whose face it is.
• Face recognition compares the face with a stored photo of the worker to confirm it is the same person. It needs a reference photo of everyone, it means handling biometric data, and it makes its own mistakes with helmets, dust and poor light.

A presence check with stored selfies is still useful. A supervisor or HR can look at the photos when something seems off, and people behave differently when they know a photo is kept. But if a vendor says a selfie “stops proxy attendance”, ask which of the two they mean.

Workers without smartphones

Many site workers do not have a smartphone, or do not want to use their own for work. The practical answer is for the supervisor to mark the gang in bulk from their own phone. That moves the trust from the worker to the supervisor, so pair it with a headcount: compare the supervisor’s marking with the labour contractor’s muster and with what you see on site visits.

Shift rules: grace, late, half-day, overtime

A punch time means nothing until the shift is defined. Set, for each site:

• Shift start and end, for example 9:00 to 18:00.
• Grace period: the minutes after the start that still count as on time, for example 10.
• Late: a punch after the grace period. Decide what repeated late marks lead to, and write it down.
• Half-day: the hours worked below which the day counts as half, for example fewer than 4.
• Overtime: the hours beyond which time is counted as overtime.

Apply the same rules to everyone on a site, put them in writing, and check they agree with your contracts and the labour laws that apply to you. A site that pours at night may need its own settings.

Privacy and consent

Location and photos are personal data. India’s Digital Personal Data Protection Act, 2023 sets out how organisations may collect and use personal data, including telling people what is collected and why, and keeping it secure. Its rules are being brought into force in stages, so ask your legal adviser what applies to you and from when.

Habits that respect workers and keep you on safe ground:

• Capture location at punch time only, not continuously through the day.
• Tell workers, in their own language, what is collected (location and a selfie when they punch), why, who can see it and how long it is kept.
• Limit who can view selfies and punch locations.
• Use the data for attendance and wages, not for purposes you have not told people about.
• Keep a fallback for anyone who cannot or will not use their own phone.

Rollout checklist for the first two weeks

Before day one

• Draw the boundary, then walk it with two or three different phones, including the cheapest one on site. Try punching in from the basement, the core and the top floor.
• Set the shift timings and thresholds for the site.
• Brief workers and supervisors in person: how to punch, what is collected, and what to do when a punch fails.
• List the workers without smartphones and assign each group to a supervisor.
• Agree the fallback when GPS or the network fails, and who approves a manual entry.

Week 1

• Run the app alongside your existing muster register. Do not change how wages are worked out yet.
• Every evening, review failed punches: where they happened and what accuracy the phone reported.
• Widen or adjust the boundary where honest workers keep being rejected.
• Fix phone problems: location permission off, battery saver limiting location, no data.

Week 2

• Compare app attendance with the register, person by person, and look into every difference.
• Check that late and half-day marks match what supervisors saw.
• Review a sample of selfies and bulk marks.
• Once the two records agree for a full week, move wages onto the app’s attendance and retire the register.

How BuildAura handles it

In BuildAura, an admin draws each site’s boundary as a polygon on Google Maps, and the punch-in check allows for the GPS accuracy the phone reports. Punch-in takes a selfie, which is checked for a face being present; BuildAura does not recognise who the person is. Shift times, grace period and the late, half-day and overtime thresholds are set per project, and supervisors can bulk-mark crews who do not have phones, so the month’s attendance is ready for payroll.