A geofence is an invisible circle drawn around a work site on a map. When a worker clocks in on their phone, the phone checks its GPS position, and the punch only counts if it's inside the circle. Done well, it's a simple way to make sure people clock in at work, not from the car park or the sofa, without buying hardware for every site. Done badly, it refuses honest punches because the circle is too small, drains batteries, or quietly turns into tracking people all day. The difference comes down to three choices: the right radius for each site, checking location only when it's needed, and telling staff exactly what's collected and why.
Laws on tracking employees' location differ a lot between countries. Some require consent, a written notice, a clear purpose or limits on how long data is kept, and some treat personal phones differently from work phones. This guide explains how geofencing works in general. It isn't legal advice. Check the rules where you operate before you start.
1. How a geofence works
There are three parts.
- The zone. You place a pin on the exact spot of each site and set a radius, for example 100 metres. That circle is the geofence.
- The reading. When a worker taps to clock in, their phone takes a GPS reading: a latitude, a longitude and an estimate of how accurate it is.
- The decision. The system measures the distance from the reading to the pin. If it's within the radius, the punch is accepted and saved against that site. If not, it's refused, ideally with a clear message.
Two details separate a reliable system from a frustrating one:
- A fresh reading. Phones cache old positions. If the app uses a reading from 20 minutes ago, someone who's just arrived may be refused, and someone who's just left may be accepted. Ask whether the app takes a new reading at the moment of the punch.
- Who decides. If only the app decides, a tampered phone can fool it. It's stronger when the server checks the distance as well.
2. Choosing the radius
The radius is the most important setting you'll make, and it should be different for each site. Too small and honest staff get refused at the door. Too big and someone can clock in from the café down the road.
A simple rule: measure from the pin to the furthest place someone would reasonably clock in, then add a margin for GPS error.
Worked example: a 120-metre site
A building site is about 120 metres across. You put the pin in the middle. The furthest gate is 60 metres away. The site is outdoors, so you add a 30-metre margin. 60 + 30 = 90 metres. Round up to 100 metres.
Typical starting points
| Site | Example radius | Why |
|---|---|---|
| Small shop or office | 30 to 50 m | One entrance, but allow for weak GPS indoors |
| Restaurant with a car park | 75 to 100 m | Staff may clock in from the back door or the car park |
| Building site | 100 to 300 m | Large area, several gates |
| Resort, farm or large estate | 300 to 500 m | Staff start at different points across the grounds |
These are starting points. Watch the refused punches for the first two weeks and adjust.
Bigger isn't free. Doubling the radius makes the area four times larger. A 50-metre circle covers about 7,854 square metres. A 100-metre circle covers about 31,416. If two of your sites are close together, overlapping circles can put punches against the wrong site.
3. GPS accuracy, indoors and out
Phone GPS is good, but not perfect, and it's much worse in some places than others.
- Outdoors, open sky. Modern smartphones are often accurate to within about 5 metres.
- Between tall buildings. Signals bounce off walls, and errors of 20 to 50 metres are common.
- Indoors. Roofs and walls block satellites. The phone falls back on Wi-Fi and mobile masts, which can be off by 50 metres or more.
- Basements, metal roofs, underground car parks. GPS may not work at all.
What this means for you:
- Indoor sites need a bigger margin, or a different method. If staff clock in deep inside a large building, a QR code at the staff entrance may work better than GPS.
- Ask staff to clock in near a door or window if a site is borderline.
- Keep an eye on refusals. If the same person is refused at the same site every day, the radius or the pin is wrong, not the person.
4. Battery and data
A common worry, and mostly a fair one, but it depends on how the app uses location.
- A reading only at the punch uses very little battery. The GPS switches on for a few seconds, twice a day.
- Continuous tracking (location every few minutes all shift) uses much more, especially on older phones. Staff will notice.
- Data use for a punch is tiny, usually a few kilobytes. But the phone does need a data connection at the moment of the punch to send it.
If staff will use their own phones and data, a check only at the punch is the fairer default. Where you need more, a company phone avoids putting the cost on staff.
5. At the punch, or all day?
This is the biggest fairness question, so be deliberate about it.
Location only at clock-in and clock-out. You learn one thing: was the person at the site when they said they started and stopped? That's usually all payroll needs.
Location at chosen stops during the shift. Useful for staff who visit several places: a carer visiting clients, a technician on call-outs. The worker records a stop at each place, and the location is saved with it.
Continuous tracking. The app records location all shift. Sometimes needed for drivers or lone workers' safety. But it's more intrusive, uses more battery, and in many places needs a stronger reason and clearer consent.
A good rule: collect the least location data that does the job. If you only need to know that people start at the site, don't track their lunch break. And never track outside working hours.
6. Consent and transparency
Even where the law doesn't require consent, being open builds trust and avoids disputes. Staff should know:
- What is collected: position at the punch only, at chosen stops, or continuously.
- When: only when clocked in, or only at the moment of the punch.
- Why: to confirm time worked at the right site, not to monitor private life.
- Who sees it: managers, payroll, nobody else.
- How long it's kept, and how they can see their own records.
- What happens when it fails: who to tell, and how the time gets fixed.
Put this in writing. Ask staff to acknowledge it, and get formal consent where your rules require it. For staff using personal phones, be extra careful. Some places limit what employers can require on a personal device.
7. Remote and field staff
Geofencing works best for people who work at known places, even if those places change daily.
- Construction crews: a zone per site. Their hours can then be split by site, which helps with job costing.
- Security guards: a zone per post, small enough to show they were at the post, not the car park.
- Home carers: each client's address as a zone. A punch on arrival confirms the visit.
- Cleaners and grounds staff: a zone per property, with a stop recorded at each one.
It works less well for people with no fixed place at all, like drivers or sales reps on the road. For them, a geofence at the depot for the start and end of the day, or clock-in by message, often fits better. The Time clock buying guide compares the options.
8. Exceptions for staff who roam
Some people legitimately can't be inside a zone when they start work: a manager who starts with a meeting off site, a driver who begins at a customer's address, a technician called out at night.
Options:
- A per-person exception. The fence doesn't block them, but the punch is still saved against a chosen site so it's recorded. Keep the list short and review it every few months.
- A temporary zone for a one-off job.
- A manager punch. The worker calls in, and a supervisor records the time with a reason.
Whatever you choose, apply it consistently. If one person on the team can clock in from anywhere and nobody knows why, others will see it as unfair.
9. What to tell staff
Before switching on geofencing, hold a short session at each site and hand out a one-page notice. A simple script:
- "From [date], you'll clock in on the app when you arrive at the site."
- "The app checks your location only when you tap Punch In or Punch Out." (Say this only if it's true.)
- "If it says you're not at the site, move closer to the entrance and try again. If it still fails, tell your supervisor, who will record your time."
- "Managers and payroll can see where each punch was made. Nobody sees your location at other times."
- "If you don't have a suitable phone, tell us and we'll arrange another way to clock in."
Then watch the first two weeks closely. Fix pins and radius quickly. People forgive a teething problem fixed in a day. They don't forgive being refused at the door for a month.
10. Set-up checklist
- Each site has its own pin, placed where staff actually clock in.
- Each radius is based on the site's size plus a GPS margin.
- Indoor or basement sites have a fallback such as a QR code or a wall clock.
- The app takes a fresh reading at the punch, and the server checks the distance.
- Location is collected only as much as needed, and never outside working hours.
- Staff have a written notice of what's collected, when, why and who sees it.
- Consent is recorded where your rules require it.
- Exceptions for roaming staff are listed, justified and reviewed.
- There's a clear way to fix a refused punch the same day.
- Refused punches are reviewed weekly for the first month.
11. Frequently asked questions
Is geofence time tracking legal?
In most places, checking location at clock-in for work purposes is allowed, often with notice or consent. Continuous tracking and tracking on personal phones are more tightly controlled in some countries. Check local rules.
What radius should I use?
Measure from the pin to the furthest point where someone would clock in, and add 20 to 30 metres for GPS error. Many sites end up between 50 and 150 metres.
Why was a worker refused when they were at the site?
Usually the pin is in the wrong place, the radius is too small, or the phone had a poor reading indoors. Moving near a door and trying again often works. If it keeps happening, fix the zone.
Does geofencing drain the battery?
A reading only at the punch uses very little. Continuous tracking uses noticeably more.
Can staff fake their location?
Some apps exist to fake GPS. A fresh reading at the punch and a server-side check make it harder, and a photo at the punch or a QR code adds another layer.
Do staff need mobile data?
Yes, at the moment of the punch, to send it. GPS itself works without data.
Is it fair to ask staff to use their own phones?
It can be, if it's explained, the app only checks location at the punch, and there's an alternative for anyone who can't or won't. ---
Want geofencing that staff can trust?
PunchClock lets you draw a zone for each site, from 20 to 500 metres. The phone takes a fresh GPS reading when someone taps Punch In, and the server checks the distance before the punch is saved against that site. You can switch on an exception for staff who roam, let people record stops during a shift, and see every punch of the day on one map.