How the Terrain Fraud Detection Works

When a surveyor writes "ascending" as they walk a section line, USGS elevation data should agree. When it doesn't, that's a data point worth investigating.

One of the more unusual features of GLOFieldNotes.com is what we call terrain analysis — an automated comparison of what the original surveyor wrote about the landscape against what the actual USGS digital elevation model shows at those coordinates.

The idea is simple. When a surveyor writes "land ascending" or "ground descending" in their field notes, the elevation should go the right direction between the geolocated points. If the surveyor wrote "level" but our USGS lookup shows a 90-foot change in elevation, something is worth a second look.

We use the USGS 3DEP (3D Elevation Program) national dataset via the TNM Elevation API. Every geolocated survey call gets an elevation lookup in NAVD88 feet. Then we compare adjacent calls on the same survey run, using the stored terrain signal — ascending, descending, level, or rolling — and the actual elevation delta.

A green "confirmed" badge means the elevation data agrees with what the surveyor wrote. An amber "discrepancy" flag means it doesn't. This is a research and due-diligence tool, not a definitive finding. Positioning errors, datum shifts, and tree-height effects on 1800s survey practices can all generate apparent mismatches. But systematic flags on the same township are worth investigating.

We're currently analyzing data across Montana, Wyoming, Utah, Colorado, Kansas, Nebraska, Oklahoma, South Dakota, and New Mexico.