Tremap: 15 million trees on a map

Tremap is a UK product for mapping and looking after trees. Its partners include the Smithsonian and Heathrow, and the global map holds more than 15 million trees. I'm the only engineer on it.

The pieces

• iPhone and Android apps built with Expo.
• A web portal for organisations that manage their trees there.
• A map API serving about 15.5 million points.
• Accounts and Stripe billing.
• QR and NFC labels, so you can scan a tree in the field and open its record.
• Offline mode, because the trees are often where the signal isn't.
• An admin panel.

The hard part

Fifteen million points don't fit on a phone, and they don't fit in a single request either. The map has to ask for what's on screen at the current zoom and nothing more, and the API has to answer quickly enough that panning feels instant. Most of the engineering effort went there. Everything around it I kept deliberately plain.

Offline

Gardeners and surveyors work in parks and estates with poor signal. The app keeps working offline, saves edits and syncs them when the connection comes back. It's the kind of feature nobody notices until it's missing.

One engineer, every layer

Because one person owns the apps, the portal and the API, a change to how a tree is stored reaches every screen in one go, and nothing waits on another team.

If you're planning a product with maps, field work or a lot of data, take a look at my other work or write to me at giorgikhimshiashvili@gmail.com.