Base Unit Tools

A City of Detroit web application for exploring and inspecting the city's base units: addresses, parcels, buildings, and streets.

Live site: https://base-unit-tools.netlify.app

What are Base Units?

Base units are the fundamental geographic units used to describe Detroit. Every location in the city can be identified by its relationship to these four types:

• Addresses - Street addresses (e.g., 2 Woodward Ave)
• Parcels - Land parcels identified by parcel ID
• Buildings - Building footprints
• Streets - Street segments

Tools

Map Explorer (/map)

Interactive map for inspecting base units. Click any feature to view its attributes and relationships.

• Search by address, parcel ID, or intersection
• Filter click interactions by mode (parcels, buildings, or streets)
• View Mapillary street imagery with historical date selection
• Drag the divider to resize panel widths

URL Parameters

Parameter	Description	Example
id	Feature ID to select	id=01001234. (parcel) or id=12345 (building/street)
layer	Layer type	layer=parcel, layer=building, layer=street, layer=address
mode	Click interaction mode	mode=all (default), mode=parcel, mode=building, mode=street
streetview	Open street view panel	streetview=true
streetviewdate	Select imagery nearest to date	streetviewdate=20240315 (YYYYMMDD format)

Example URLs:

• /map?id=01001234.&layer=parcel - View a specific parcel
• /map?id=12345&layer=building&streetview=true - View building with street view open
• /map?id=01001234.&layer=parcel&streetview=true&streetviewdate=20230601 - Parcel with June 2023 imagery

Geocoder (/geocoder)

Batch geocoding tool for enriching address data.

• Upload a CSV containing Detroit addresses
• Each address is matched against the City's geocoder
• Download results with parcel IDs, coordinates, council district, and other attributes
• Supports partial matches and displays match quality scores

Mailer (/mailer)

City employees only. Generate mailing lists of property owners within a geographic area.

• Draw a polygon, line, or point on the map
• Or select from preset boundaries (neighborhoods, council districts, etc.)
• Apply buffers to expand or create ring-shaped selections
• Download address lists as CSV for mail campaigns

Development

npm install    # Install dependencies
npm start      # Start dev server at http://localhost:5173
npm run build  # Production build to dist/
npm run serve  # Preview production build

Tech Stack

• React 18 + Vite
• MapLibre GL JS for mapping
• Radix UI + Tailwind CSS for styling
• ArcGIS REST APIs for feature services and geocoding
• Mapillary for street-level imagery

Deployment

Deployed to Netlify and Cloudflare Pages. Build output is the dist/ folder.

Data Sources

• Feature services hosted on ArcGIS Online (services2.arcgis.com)
• City of Detroit Geocoder (opengis.detroitmi.gov)
• Mapillary street imagery (captured by codgis)

License

MIT License - see LICENSE