Lance-TS

Opinionated TypeScript client for the U.S. Census Geocoder API.

Turn U.S. addresses into latitude/longitude coordinates using the free Census Bureau Geocoder. Strongly-typed, totally node-native.

Read the docs

Use Case:

If you're working with U.S. address data, the Census Geocoder is an extremely viable, completely free API. Backed by the official MAF/TIGER address database, and covering virtually every U.S. address, it has no posted rate limits and no API key.

The Issue:

The raw Census Geocoder API response is verbose and awkward to work with. Below is the simplest possible response; a single one-line address match:

{"result": {
     "input": {
          "address": {"address": "4600 Silver Hill Rd, Washington, DC 20233"},
          "benchmark": {
               "isDefault": true,
               "benchmarkDescription": "Public Address Ranges - Current Benchmark",
               "id": "4",
               "benchmarkName": "Public_AR_Current"
          }
     },
     "addressMatches": [{
          "tigerLine": {
               "side": "L",
               "tigerLineId": "76355984"
          },
          "coordinates": {
               "x": -76.92748724230096,
               "y": 38.84601622386617
          },
          "addressComponents": {
               "zip": "20233",
               "streetName": "SILVER HILL",
               "preType": "",
               "city": "WASHINGTON",
               "preDirection": "",
               "suffixDirection": "",
               "fromAddress": "4600",
               "state": "DC",
               "suffixType": "RD",
               "toAddress": "4700",
               "suffixQualifier": "",
               "preQualifier": ""
          },
          "matchedAddress": "4600 SILVER HILL RD, WASHINGTON, DC, 20233"
     }]
}}

For applications that require lightweight & simple coordinate responses, lance-ts provides a clean, strongly-typed interface so you can go from address → coordinates in one call.

• 🆓 Free — no API key, no account, no rate limits
• 🏛️ Official Data — calls the U.S. Census Bureau Geocoder
• 📦 Lightweight — no HTTP library dependencies; uses node-native fetch

Installation

# pnpm (recommended)
pnpm add lance-ts

# npm
npm install lance-ts

# yarn
yarn add lance-ts

Requires Node.js 18+ (for native fetch).

Quick Start

import { geocodeOneLineAddress } from "lance-ts";

const result = await geocodeOneLineAddress(
  "1600 Pennsylvania Avenue NW, Washington, DC 20500"
);

if (result) {
  console.log(result.coordinates.x);  // 38.8987...
  console.log(result.coordinates.y);  // -77.0353...
  console.log(result.matchedAddress);  // "1600 Pennsylvania..."
}

How It Works

lance-ts sends your address to the Census Bureau's public REST endpoint:

https://geocoding.geo.census.gov/geocoder/locations/onelineaddress

The response is parsed and normalized, extracting the matched coordinates and canonical address from the Census Bureau's nested JSON structure, and returned as a clean, typed object.

Getting Started

# Install dependencies
pnpm install

# Run tests
pnpm test

# Run tests with UI
pnpm test --ui

Project Structure

lance-ts/
|--src/   # TypeScript source
|--dist/  # Compiled output (generated)
|--tsconfig.json
|--package.json

Limitations

• U.S. addresses only
• Coordinate results are interpolated from TIGER address ranges. Very small error margin, but not always rooftop-precise.
• Reverse geocoding (coordinates -> address) is not yet implemented. Coming soon!

Resources

• Census Geocoder Web Interface
• Census Geocoder API Docs
• MAF/TIGER Database Overview

License

ISC © matt-the-thew