2d:null 2e:["$","title",null,{"children":"Geocoding with US Census Geocoder vs Nominatim | Jim | Observable"}] 33:T5d4,# Geocoding with US Census Geocoder vs Nominatim Geocoding is the process of determining geographic position from street addresses (or place names). Here I compare two geocoding services, mainly as an exercise in working with different types of APIs. | Census | Nominatum - |-|- Info: | [Census Geocoder](https://geocoding.geo.census.gov/geocoder/) | [Nominatim](https://nominatim.org/) API: | [Census Geocoding Services API](https://geocoding.geo.census.gov/geocoder/Geocoding_Services_API.html) | [Nominatim Search API](https://nominatim.org/release-docs/develop/api/Search/) Method: | [`JSONP`](https://en.wikipedia.org/wiki/JSONP) via [tmcw/jsonp](https://github.com/tmcw/jsonp) by [Tom MacWright](/@tmcw) | `GET` via `fetch` My conclusion is that Nominatim is more flexible (able to match partial address fragments, whereas Census Geocoder requires more complete addresses), more comprehensive (able to geocode place names and points of interest as well as street address), and more straightforward to query from the browser (supporting `fetch` requests, whereas Census Geocoder seems to provide no accommodation for [cross-origin requests](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CORS), requiring more roundabout methods). On the flip side, sometimes this flexibility means Nominatim returns duplicate or unnecessary matches, especially in cases where multiple businesses may share an address. These results could be filtered with more specific search parameters.34:[] 31:{"id":"4739b6f380d14f26","slug":"geocoding-census-vs-nominatim","title":"Geocoding with US Census Geocoder vs Nominatim","thumbnail":"ad52f6ccaa0307d787af8061f79a34bbdac5378f922e7912c48da6dee7c1c24f","access_level":"public","create_time":"$D2025-07-01T03:01:07.861Z","update_time":"$D2026-01-20T20:22:34.608Z","view_time":null,"first_public_time":"$D2025-07-05T20:54:04.955Z","has_unpublished_edits":null,"fork":false,"stars":0,"starred":false,"owner":{"type":"team","id":"2800813008160316","login":"anoved","name":"Jim","avatar_url":"https://avatars-next.observableusercontent.com/0fb3dfff35196c46f19129bf9fbff47fd5a38d53dde09e0c9b40afac9955c0ba","tier":"starter_2024"},"version":473,"publish_version":null,"role":null,"authored":false,"authors":[{"type":"individual","id":"fdf70a3cc8779b08","login":"anoved","name":"Jim DeVona","avatar_url":"https://avatars-next.observableusercontent.com/0fb3dfff35196c46f19129bf9fbff47fd5a38d53dde09e0c9b40afac9955c0ba","tier":null}],"members":[{"type":"team","id":"2800813008160316","login":"anoved","name":"Jim","avatar_url":"https://avatars-next.observableusercontent.com/0fb3dfff35196c46f19129bf9fbff47fd5a38d53dde09e0c9b40afac9955c0ba","tier":"starter_2024","role":"editor"},{"type":"individual","id":"fdf70a3cc8779b08","login":"anoved","name":"Jim DeVona","avatar_url":"https://avatars-next.observableusercontent.com/0fb3dfff35196c46f19129bf9fbff47fd5a38d53dde09e0c9b40afac9955c0ba","tier":null,"role":"editor"}],"comments":[],"custom_thumbnail":false,"trashed":false,"lapsed":null,"subscribed":null,"forks":0,"collection":{"id":"75d93e7d88cb698f","slug":"techniques","title":"Techniques","owner":{"id":"2800813008160316","login":"anoved","name":"Jim"}},"type":"notebook","body":{"title":"Geocoding with US Census Geocoder vs Nominatim","cells":[{"id":0,"value":"$33","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":251,"value":"## Geocoding Query:\n\nExperiment by entering a [U.S.] address or address fragment here. The same query will be submitted to both services. Compare the [Census response](#censusresponse) and [Nominatim response](#nominatimresponse) values below. Note differences in the number of matches, the information returned about each match, and the query detail required to match at all.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":131,"value":"viewof sq =Inputs.text({label: \"Geocoding query:\", placeholder: \"Enter an address here\", submit: true, width: width})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":133,"value":"encodedSearchTerm = encodeURIComponent(sq)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":238,"value":"## Census Response:","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"censusresponse","database":"$undefined"},{"id":115,"value":"gq_census = encodedSearchTerm == \"\" ? null \n : jsonp(\"https://geocoding.geo.census.gov/geocoder/locations/onelineaddress?benchmark=4&format=jsonp&address=\" + encodedSearchTerm)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":147,"value":"asTable(gq_census, {height: 128})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":287,"value":"lln_census = gq_census === null ? [] \n : gq_census.result.addressMatches.map(m => new Object({lon: m.coordinates.x, lat: m.coordinates.y, name: m.matchedAddress}))","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":386,"value":"\n \n \n \n \n \n \n \n \n ${lln_census.map(m => htl.html`\n \n \n \n `)}\n \n

Longitude	Latitude	Address
${m.lon}	${m.lat}	${m.name}

","pinned":false,"hidden":false,"mode":"html","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":248,"value":"## Nominatim Response:","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"nominatimresponse","database":"$undefined"},{"id":152,"value":"gq_nominatim = encodedSearchTerm === \"\" ? null\n : q(\"https://nominatim.openstreetmap.org/search?countrycodes=US&format=jsonv2&q=\" + encodedSearchTerm)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":154,"value":"asTable(gq_nominatim, {height: 128})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":293,"value":"lln_nominatum = gq_nominatim === null || gq_nominatim.length == 0 ? []\n : gq_nominatim.map(m => new Object({lon: parseFloat(m.lon), lat: parseFloat(m.lat), name: m.display_name}))","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":389,"value":"\n \n \n \n \n \n \n \n \n ${lln_nominatum.map(m => htl.html`\n \n \n \n `)}\n \n

Longitude	Latitude	Address
${m.lon}	${m.lat}	${m.name}

","pinned":false,"hidden":false,"mode":"html","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":409,"value":"### GeoJSON","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":422,"value":"Bonus: attempt to package lat/lon/address results as minimal [GeoJSON](https://www.rfc-editor.org/rfc/rfc7946).","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":336,"value":"// convert an array of lat/lon/name objects to minimal GeoJSON\nfunction geojsonify(lln) {\n return new Object({\n type: \"FeatureCollection\",\n features: lln.map(m => new Object({\n type: \"Feature\",\n geometry: new Object({\n type: \"Point\",\n coordinates: [m.lon, m.lat]\n }),\n properties: {\n id: m.name\n }\n }))\n });\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":343,"value":"gj_nominatum = geojsonify(lln_nominatum)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":338,"value":"gj_census = geojsonify(lln_census)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":299,"value":"### Imports & Utilities","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":6,"value":"function q(query) {\n const info = fetch(query, {\n method: \"GET\"\n }).then(r => {\n if (!r.ok) throw new Error(r.status);\n return r.json();\n });\n return info;\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":107,"value":"jsonp = require(\"@tmcw/jsonp@0.2.2\")","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":468,"value":"Fabian Iwand's Table Inspector is a handy alternative to the built-in object viewer:","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":144,"value":"import {asTable} from \"@mootari/table-inspector\"\n","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":94,"value":"### Notes\n\nSources I found helpful in figuring out how to query the Census Geocoder:\n\n* https://jvaneyck.wordpress.com/2014/01/07/cross-domain-requests-in-javascript/\n* https://maptimesea.github.io/2015/03/03/gecoding-api.html\n* https://stackoverflow.com/questions/68010817/why-is-the-url-malformed-in-get-request-with-fetch-api-in-javascript","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"}],"files":"$W34","stdlib":"1","titling":"auto"}} 32:"$31:body"