# SitePulse — Industrial Site & Construction Verification

> Detect whether construction or site change happened at any coordinate, from
> Sentinel-2 satellite imagery. $1.50/check via x402 or API key.

## Endpoints
- GET /v1/site?lon={lon}&lat={lat} — 12-month change check ($1.50)
- GET /v1/timeline?lon={lon}&lat={lat} — 36-month monthly series ($6.00)
- GET /tryit?lon={lon}&lat={lat} — free, 3/day per IP

## What you get
change_detected, change_direction (built-up | revegetated | none), confidence,
NDVI/NDBI deltas, baseline vs recent windows, and the per-scene evidence
(dates, cloud %, valid pixel counts) behind the answer.

## Resolution limit (read this)
Sentinel-2 is 10m/pixel. Reliable for commercial/industrial footprints (~30m+):
warehouses, fabs, data centres, solar farms, mines, port yards.
NOT reliable for single-family homes.

## Payment
- x402: USDC on Base or Solana — no signup
- API Key: Authorization: Bearer sp_live_... — purchase at https://sitepulse.waltsoft.net
- Tiers: Starter ($49), Pro ($149), Enterprise ($499)

## Example
GET https://sitepulse.waltsoft.net/v1/site?lon=-97.6206&lat=30.2216

## Method
1. Query the free Sentinel-2 STAC API for scenes intersecting the coordinate.
2. Discard scenes above 20% cloud cover.
3. Sample up to 12 scenes evenly across the window.
4. Read a 120m window from the red, nir and swir16 bands via COG range requests.
5. Mask per-pixel using the SCL (Scene Classification Layer) band — cloud, shadow,
   cirrus and snow classes are dropped. This is a lookup, not a model.
6. Compute masked mean NDVI and NDBI per scene.
7. Compare the earliest third of the series against the latest third.
8. Flag "built-up" only when NDVI falls AND NDBI rises — requiring both suppresses
   seasonal vegetation swings, which move NDVI without moving NDBI.

## Credit unit
1 credit = $0.010. 150 credits per /v1/site call,
600 per /v1/timeline call.

## Data source & licence
Sentinel-2 L2A, ESA/Copernicus, via the AWS Registry of Open Data
(s3://sentinel-cogs, us-west-2). Free, full and open access.