Terra Firma
Compare parcel elevation and flood exposure
Overview
Terra Firma ranks parcels in the current map view by elevation and shows FEMA flood-zone context at a glance. Parcels are colored relative to each other within the viewport — high ground appears brown, low ground appears green-blue — making it easy to spot elevation differences across a neighborhood.
How to use
Navigate to an area
Pan and zoom to the area you want to inspect. The app requires zoom level 15 or higher to load parcel data (up to 12,000 parcels per view).
Read the elevation colors
Parcels are colored by elevation percentile within the current viewport. Brown tones indicate higher ground; green-blue tones indicate lower ground. The elevation range (min to max) is displayed in the panel.
Search an address
Use the address search to find and highlight a specific parcel. The matched parcel is outlined in blue with a white casing.
Inspect parcel details
Click any parcel to see its elevation, percentile rank, flood zone classification, and acreage. Parcels in high-risk flood zones are flagged.
Elevation ranking
Elevation is computed relative to the parcels visible in the current viewport, not as an absolute national ranking. When you pan or zoom, the ranking recalculates for the new set of parcels. This makes it easy to compare elevation within a neighborhood or across a floodplain.
Data layers
Parcel boundaries, addresses, and acreage from the nationwide parcel layer.
National Flood Hazard Layer — official flood zones and base flood elevations used to flag high-risk parcels.
1-meter digital elevation model (DEM) providing ground elevation for each parcel.
Sharing
The map URL encodes the center point and zoom level, so you can share a specific view. The URL parameters are lat, lon, and zoom.