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TerrAlert uses Sentinel-2 Level-2A optical imagery (10 m per pixel) from the European Union's Copernicus programme, downloaded from the Copernicus Data Space with the EODAG library. It is open data, so there is no imagery licensing cost passed to you. Detections can also be compared with public signals recorded nearby, such as NASA FIRMS active fires and GLAD and RADD forest-loss alerts. The credits these sources require are listed in section 18 of our Terms of Service.

We do not publish an accuracy figure, because we do not yet have one measured on our own pipeline that we would stand behind. Every detection carries a model score, and a before-and-after pair of the actual images, so you can judge it yourself. Each area also has an alert policy: confidence, the default, sends an alert when the detection clears the area's minimum model score (0.60 unless you change it) and the change is still there on the next clear image, compared with an earlier one, so the alert comes one clear pass after the change; corroborated sends one only when an independent source that can see that kind of change has recorded it on or near the detection between its two images or a few days after (NASA FIRMS for fire, GLAD or RADD for forest loss, NASA flood maps for flooding). Construction and urban expansion have no such source at present, so under corroborated they alert only if you mark them real in Triage. A detection raised by NASA FIRMS, GLAD or RADD itself alerts under either policy once its feed confidence reaches the area's minimum, and says it is that feed's report, not verified by TerrAlert. Detections that do not alert still appear in the dashboard and the weekly digest.

You get an alert when a new clear image shows a change that passes your area's alert policy, so alerts depend on the ground, not on a schedule. How often TerrAlert checks for new imagery depends on your plan:

Free: about twice a week
Starter and Growth: about twice a day
Pro and Enterprise: every few minutes

Checking is not the same as finding. Sentinel-2 passes a given place every few days and cloud makes many passes unusable, so expect a change to be detected within about a week, not the same day.

Optical satellites cannot see through cloud. When too much of your area is under cloud in an image, that image is not compared, and the pipeline waits for the next clear one. In persistently cloudy seasons an area can go weeks without a usable image.

Sentinel-2 images land between about 56°S and 84°N, so you can draw an area anywhere in that range. You can draw an area of any size, up to your plan's maximum. An area smaller than 10,000 m² or narrower than 100 m is watched through a box at least 100 m across around it, and a change must be roughly 50 m across before it can be reported. TerrAlert is not available in Cuba, Iran or North Korea.

Choose a plan on the Pricing page, or manage your subscription on the Billing page in the app. Payment is handled by Stripe. Prices are in US dollars and exclude tax, which is added at checkout where it applies. Plan changes are made in the Stripe billing portal linked from the Billing page, which shows when a change takes effect, and any prorated charge or credit, before you confirm. Paid plans renew every month until you cancel. To cancel, on any plan, click Cancel subscription on the Billing page: the plan stays active until the end of the period you have paid for, and the account then continues on the Free plan. Your full history is kept for 60 days after the subscription ends, so you can switch provider or retrieve it; Download my data on the Account page exports all of it, including your areas with their settings and your detections with their geometry. After 60 days the Free plan's 30-day history window applies.

Your account, area boundaries and detections are stored in a PostgreSQL database on our servers at DigitalOcean in the United States, with the processed satellite imagery for your areas. All connections use TLS 1.2 or 1.3. Webhook signing secrets are encrypted in the database; beyond that we rely on the hosting provider's disk-level defaults and do not claim full encryption at rest. Our Security page lists what is and is not in place. You can export your data or delete your account from the Account page, as our Privacy Policy describes.

Webhooks are included on Starter and above, and are not available on Free. On the Account page, add a webhook URL; TerrAlert creates a signing secret and shows it once (through the API you can supply your own of at least 16 characters). When an alert fires, TerrAlert sends an HTTP POST with a JSON payload, signed with HMAC-SHA256 in the X-TerrAlert-Sig header. A Slack or Microsoft Teams incoming-webhook URL receives a readable chat message instead. A failed delivery is retried with exponential backoff, up to 5 attempts in total. The payload and how to verify the signature are in the webhook guide.

Check these in order:

1. Visit /status and confirm all services are operational
2. Check the area in the dashboard: is it active, which change types does it watch, and what are its alert policy and minimum model score?
3. Check the Alerts page for delivery history, and your spam folder for email alerts
4. For webhooks, check your endpoint returns a 2xx status; the Test button on the Account page sends a test delivery
5. Check cloud cover for your region: cloudy images are skipped

If none of the above resolves it, contact support with your AOI ID.

Yes. Enterprise plans are configured to what you need: 30 or more areas of up to 5,000 km² each, imagery checks every 5 minutes, the length of detection history you choose, and a named support contact. Enterprise customers can also negotiate a written service level agreement. Contact us with your use case and estimated AOI count and we will put together a quote.