USGS Elevation Point

The USGS Elevation Point Query Service over the 3D Elevation Program (3DEP): best-available elevation for any US coordinate. Machine-payable per request.

Robinhood Chain

Offers

Offer	Endpoint	Price
Point elevation 3DEP elevation for a point. Pass ?x=-77.03&y=38.9&units=Meters.	`/m/usgs-epqs/elevation`	0.002 USDG

Machine-readable: openapi.json with x-payment-info offers.

Try it live

Run the full MPP flow from your browser: catch the 402, sign the payment with your wallet, and watch it settle on-chain.

Pay with an agent

Any MPP or x402-compatible client works. With mppx, payment is automatic:

// x402 exact scheme (permit2) on Robinhood Chain
// 1. GET the endpoint, read the payment-required header (base64 JSON)
// 2. Sign PermitWitnessTransferFrom against Permit2 for the advertised offer
//    (spender = x402ExactPermit2Proxy, witness.to = merchant wallet)
// 3. Retry with the payment-signature header; settlement tx arrives
//    in the payment-response header
const res = await fetch('https://api.meshgateway.co/m/usgs-epqs/elevation', {
  headers: { 'payment-signature': signedPaymentPayload },
})

Or inspect the challenge yourself:

curl -i https://api.meshgateway.co/m/usgs-epqs/elevation
# HTTP/1.1 402 Payment Required
# WWW-Authenticate: Payment id="…", method="evm", intent="charge", …