About & coverage

Basesheet turns an address into the first sheet of a site design: what's on the ground, what's regulated, and where the data came from. It's built for landscape architects, civil engineers, architects and developers doing early site work.

What you get

• Base plan in State Plane feet: parcel line, neighboring parcels (ID, and owner and deed/plat reference where the county publishes them), road centerlines and names, approximate right-of-way, contours (LiDAR where available), slope bands, soils, FEMA flood zones, NWI wetlands, aerial underlay.
• Files: DXF (true coordinates, and a copy moved near 0,0 for SketchUp), textured 3D terrain (COLLADA for SketchUp, OBJ for Rhino/Blender), LandXML surface for Civil 3D, GeoJSON layers and a GeoTIFF elevation model for GIS, KML for Google Earth.
• PDF summary: scaled sheets with north arrow, scale bar and legend, plus a findings sheet that flags floodplain, wetlands, steep slopes and problem soils in plain language.
• Provenance log: every layer's source, date, resolution and known limits. Layers that fail to load are marked as missing, never silently dropped.

What it isn't

• Not a survey. Parcel lines are assessor tax lines, typically 5-50 ft from the legal boundary.
• No zoning, setbacks, easements, utilities or local critical-area maps (except the experimental Thurston County, WA test fit). Right-of-way is approximated from the gaps between tax parcels, not taken from recorded plats.
• Not a wetland delineation, geotechnical report or flood determination.

PLANNING-LEVEL DATA ONLY. Compiled from public GIS sources of varying resolution and vintage. Not a substitute for a boundary or topographic survey by a land surveyor licensed in the site's state. Parcel lines are assessor tax lines, not legal boundaries. Verify all conditions in the field.

Open source

The base plan code and the parcel source list are open source (MIT) at github.com/hthillman/site-base-plan. If your county publishes parcels and isn't covered, you can add it: it's one small file. See the contributing guide there.

Coverage

Topography, soils, flood zones, wetlands and imagery cover all 50 states. Parcel lines come from free statewide parcel layers, which 30 states publish:

No free statewide parcel layer yet (the plan is drawn around the address instead): Alabama, Arizona, California, Illinois, Iowa, Kansas, Kentucky, Louisiana, Michigan, Mississippi, Missouri, Nevada, New Mexico, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Texas.

Elevation: USGS 3DEP. Most of the country has 1 m LiDAR; where it doesn't, the elevation model is 3-10 m and the tool raises the contour interval to what the data supports (5 ft at 10 m) and says so.

Experimental: apartment test fit

For parcels in Thurston County, WA (Olympia, Lacey, Tumwater and surrounding areas), an experimental mode looks up the zoning, removes setbacks and buffers, and proposes walk-up apartment and parking layouts that meet the district's density, parking, coverage and height rules. Its rule sheets are AI-extracted from the codes and not yet reviewed, so it's off by default.

Common questions

How do I get a base plan for a property?

Type the street address (or a parcel number and state) on the home page and select Build base plan. In about 15 to 30 seconds you get a zip with CAD, 3D, GIS and PDF files for the parcel plus a buffer around it (100 ft by default).

What files do I get?

A DXF in State Plane feet for AutoCAD and Civil 3D, a copy moved near 0,0 for SketchUp, textured 3D terrain (COLLADA and OBJ), a LandXML surface, GeoJSON layers and a GeoTIFF elevation model for GIS, a KML for Google Earth, and a PDF with scaled sheets and plain-language findings about floodplain, wetlands, steep slopes and soils.

Where does the data come from?

Public sources, queried live for each site: USGS 3DEP LiDAR for topography, USDA NRCS SSURGO for soils, the FEMA National Flood Hazard Layer, the USFWS National Wetlands Inventory, Census TIGER roads, Esri World Imagery, and free statewide or county parcel layers. Every download includes a provenance file with each layer's source, date and resolution.

Is this a survey?

No. It's planning-level data for early site work. Parcel lines are assessor tax lines, often 5 to 50 ft from the legal boundary, and wetlands and flood zones are screening maps. Use a licensed land surveyor and the appropriate specialists before design decisions that depend on exact boundaries or conditions.

Which states have parcel lines?

30 states publish a free statewide parcel layer it can use, plus 18 Georgia counties so far. Elsewhere the plan is drawn around the address without a parcel line; everything else still works. The coverage table above lists each state.

How accurate are the contours?

They come from the best USGS 3DEP elevation data at the site: usually 1 m LiDAR, sometimes older 3 m LiDAR or a 10 m model where there's no LiDAR. The tool raises the contour interval to what the data supports (5 ft at 10 m) and says so.

Can I use it with SketchUp?

Yes. In SketchUp, use File, Import, choose COLLADA (.dae) and pick terrain.dae for textured 3D ground with the parcel line on it. site-local.dxf has the linework in the same coordinates for SketchUp Pro.

Does it cost anything? Is it open source?

It's free with no account. The base plan code and parcel source list are open source under the MIT license on GitHub.