How lotcheck works
lotcheck turns a Georgia street address into a plain-language site report: flood zone, elevation and slope, wetlands, jurisdiction, soils, and (in supported counties) parcel detail. It is built on free, public government data. It is a screening tool, not a survey or a flood determination. See the limits and disclaimer below.
The pipeline is deterministic
When you run a report, lotcheck geocodes the address, then queries each data source independently and assembles the result. There is no AI in the data path: every number and classification you see comes straight from a government dataset, and each card names its own source. If one source is slow or down, that card shows an error and the rest of the report still returns.
Two optional features do use a language model, and they are clearly separate from the data: the plain-English summary and LotCheck Pro.
Where the data comes from
All of these are free, public APIs operated by federal agencies, the state, or counties. lotcheck does not add or invent data; it reads these and presents them.
| Report card | Source | What it provides |
|---|---|---|
| Flood zone | FEMA National Flood Hazard Layer (NFHL) | The mapped FEMA flood zone and whether the point is in a Special Flood Hazard Area. |
| Elevation & slope | USGS 3DEP elevation service (EPQS as a fallback) | Ground elevation sampled across the lot, from which relief and max gradient are computed. |
| Wetlands | National Wetlands Inventory (USFWS), via the GA Coastal Resources mirror | Whether mapped wetlands fall on the parcel or nearby. |
| Jurisdiction | U.S. Census TIGERweb | Whether the point is in an incorporated city or unincorporated county. |
| Soils | USDA SSURGO, via Soil Data Access | The dominant mapped soil, drainage class, and hydrologic group. |
| Geocoding | U.S. Census Geocoder | Turns the address into coordinates, the county, and the FIPS code. |
| County parcel | Each county's own public GIS | Parcel boundary, acreage, zoning, and (Cherokee only) utilities, permits, and future-conditions floodplain. |
| Map tiles | OpenStreetMap | The background map shown on screen and in the printed report. |
County coverage
Federal and state data (flood, elevation, wetlands, jurisdiction, soils) covers every Georgia address. Parcel detail comes from each county's own GIS, which lotcheck currently reads for 13 metro-Atlanta counties: Fulton, DeKalb, Gwinnett, Cobb, Clayton, Henry, Fayette, Rockdale, Forsyth, Paulding, Coweta, Douglas, and Cherokee. Cherokee additionally returns utility lines, permits, and future-conditions floodplain. Addresses outside those counties get the full federal and state report without the parcel card.
What it can and cannot tell you
- Geocoding can land on the wrong spot. The free address data lags new streets and subdivisions, so a brand-new street can be snapped to a similarly-named older one. lotcheck warns you when the matched street differs from the one you typed, and gives you a Google Maps link to confirm. Always sanity-check the marker on the map.
- FEMA maps can be out of date, revised, or simply unmapped. The absence of a mapped flood zone is not a guarantee of no flood risk.
- There is no septic or perc-test data anywhere in public layers. Soil drainage class is only a proxy for septic suitability, never a result.
- Soils and wetlands are mapped at landscape scale, not at the scale of a single building pad, and the elevation model cannot see a rock ledge, a soft spot, or a sinkhole.
- County GIS can lag the authoritative county portal. Acreage, zoning, and utility lines are read from the GIS and should be confirmed for anything important.
In short: lotcheck is a fast first screen. Anything you are going to rely on should be confirmed by a licensed surveyor, the county, and a FEMA determination.
The optional plain-English summary
The "Plain-English summary" checkbox writes a short paragraph describing the data already computed above it. It runs on a small open-source model on our server, using a key we hold and pay for, and it is rate-limited and spend-capped. It only ever sees the report data, never anything about you, and it is purely a readability convenience. You can turn it off.
LotCheck Pro and your API key
LotCheck Pro is an optional deeper analysis written by a frontier Claude model. It is bring-your-own-key: you paste your own Anthropic API key, and you pay Anthropic directly for what it uses. Here is exactly how your key is handled.
- Your key never touches our server. The request goes straight from your browser
to
api.anthropic.com(using Anthropic's documented direct-browser-access header). lotcheck's server is not in the loop and never receives, logs, or proxies your key. - It is stored only in your own browser. If you tick "Remember key in this
browser," the key is saved in your browser's
localStorageon your device. That is a private, per-browser store; it is not a cookie and it is not transmitted anywhere by us. If you leave the box unticked, the key is used for that one request and not saved at all. - You can remove it at any time. Untick "Remember key" and reload, or clear your browser's site data for this site. Either one deletes the stored key from your device.
- The optional "Web research" toggle in Pro lets Claude run a few web searches for market context. Those searches are billed to your Anthropic key too, which is why it is a checkbox you control per run.
Because the key stays in your browser, you should still treat it like a password: only paste it on a device you trust, and prefer a key with a spend limit set in your Anthropic account.
Privacy
- No account, no login, no tracking pixels.
- We keep minimal, short-lived request information (such as the rounded coordinates of a lookup) to cache results and to rate-limit abuse. We do not sell data.
- Reports are cached by approximate location so a popular address does not re-hit the upstream services on every view. The cache holds the public report data, nothing about who looked it up.
- Your Anthropic API key is never part of any of this. See above.
Disclaimer
lotcheck is informational only. It is not a survey, a flood determination, a title search, a septic approval, or professional due diligence, and it does not tell you whether to buy. Verify flood status through a FEMA Letter of Map Amendment and a licensed surveyor, confirm parcel and zoning details with the county and city, and have a perc test and geotechnical investigation done where they matter, before relying on anything here.