GPS-verified time tracking for a small field crew

Why the owner wanted a new timesheet

A small crew works across several job sites, and the owner can’t be at all of them. Without the right tool, hours are reported after the fact, and there’s no easy way to tell whether time was logged from the job or from somewhere else.

Off-the-shelf time trackers either ignore location or treat it as a hard gate: out of range, no clock-in. That’s a bad trade for a real crew. Sometimes a worker is on a supply run, the GPS is weak, or the job site pin is a little off. Blocking them loses real hours and creates friction.

The owner wanted something simpler and fairer: record where people are, let them log their time either way, and show the owner the entries that deserve a second look.

How we approached it

We designed the whole app around one rule: never lose a real hour, and never hide a questionable one.

1. Job sites with a fence. The owner creates each job site on a satellite map and sets how far the fence reaches, from 100 to 1,000 feet.
2. Two GPS checks per timer. The phone records where the worker is when the timer starts and again when it stops. Manual entries get a check too.
3. Flag, don’t block. Entries outside the fence are saved with the real distance and a plain-English note, like “Marcus was on-site when starting the timer but 15 mi away when stopping.” The owner approves or rejects them.

Every entry also asks “What did you accomplish?”, so the hours come with a short record of the work.

How the location check works

The app measures the straight-line distance from the worker’s phone to the job site’s pin and compares it with that site’s fence. Location is only captured at the moment of clocking in, clocking out or entering time, not tracked all day.

What else it does

• Invite-only accounts. The owner invites each person by email; there’s no public sign-up.
• Timer or manual entry, including backdated entries for a day someone forgot to clock in.
• A running timer survives the app closing, with a reminder notification to clock out.
• Owner tools: edit or delete entries, archive finished job sites, manage the team, and export filtered hours as CSV by email.
• Worker history, so each person can see their own hours for the week and month.

Built with

• Flutter: one codebase for iPhone and Android, phones and tablets.
• Firebase Authentication and Firestore: accounts, job sites and time entries, with security rules so workers only see their own time.
• Cloud Functions: invitations, account control and CSV exports.
• GPS and satellite maps: location capture on the phone and job-site maps for the owner.

What changed for the owner

The owner gets hours they can trust, with the context to judge the exceptions, and the crew gets an app that doesn’t punish them for a bad GPS signal.

• Exceptions come to the owner. Flagged entries sit at the top of the dashboard with the distance and the worker’s note.
• No lost hours. Being off site never stops anyone from logging time; it only asks for a second look.
• Payroll starts from a clean spreadsheet. Filtered exports arrive by email.
• It’s theirs. The app is published under the client’s own Apple and Google developer accounts, and runs for effectively nothing at this crew size.

Need an app built around how your crew actually works?

This project is a good example of a small, focused app solving one specific problem well. Off-the-shelf tools almost fit; the details that make it fair to the crew are what made it worth building.

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Questions about GPS time tracking