Overview
This page lays out some of the differences between our service and
OpenStreetMap's Nominatim service,
and hopefully helps make the transition to the OpenCage
geocoding API as easy as possible.
Comparing geocoding services?
See our Geocoding Buyer's Guide for a full list of all the factors to consider.Technical differences in API request and response
Take a look at our API documentation for the full details (don't worry it is a single page), but here we attempt to layout some of the key conceptual differences between the two services.
API End Points |
The OpenCage geocoding API has a single end point for both
forward and reverse geocoding.
Nominatim has multiple different end points. |
Authentication |
We require an API key, supplied in the
key=
parameter.
You will find your key in your account dashboard. OpenStreetMap's hosted Nominatim doesn't require authentication but does ask you to supply an email
|
Query Parameters |
Nominatim requires different parameters depending on which end
point you are querying and the type of query
you are making, for example the
q=
parameter for forward geocoding and
lat=
and
lon=
for reverse geocoding.
We instead require
q=
for both forward and reverse geocoding.
See the
request format documentation
where you can also learn about the
various optional parameters we support.
|
Output Formats |
We support JSON, XML, and GeoJSON.
Nominatim supports XML, HTML, and two versions of JSON. |
Structured Queries |
Nominatim supports some types of structured queries. We do not. This is intentional, our goal is to keep the service as simple as possible for developers to comprehend and get productive with our service. Please follow the steps laid out in our guide to query formatting. |
Annotations |
By default we provide lot of other relevant information about the location of each result, things like the local timezone, currency, various other ways of referring to the locations (geohash, what3words, etc), and much more. We call these annotations. You can use an optional parameter to request additional information from Nominatim, but only the information that is in OSM. |
Address Components |
Both services return different components of the location
hierarchy, Nominatim does this in a field called
address,
we do it in the
components
portion of the result.
Learn more about our
components.
The comprehensiveness and values may differ between the two
services.
|
Display Name |
We convert the various pieces of the address (the components)
into a well formatted (according to the norms of the local
country) display name. You can find this in the
formatted
field of our response.
Nominatim returns a field called
display_name
with relevant information but it is not in the format of local
addresses. It is just a comma separated list in smaller to larger
order of the pieces of the address.
As an example, if you geocode the coordinates
52.51627,13.37769
we return the correct address format for Germany:
Brandenburg Gate, Pariser Platz 1, 10117 Berlin, Germany
Nominatim returns correct information, but not formatted
correctly:
Brandenburg Gate, 1, Pariser Platz, Mitte, Berlin, 10117, Germany
|
Location Type |
Nominatim returns the type of match in a field called
type.
We provide a
confidence score
that tells you the size of the result.
Separately we also provide the
_type
and
_category
values in the
components
portion of the result.
|
One final thing ...
If you do run your own Nominatim we encourage you to join us in also contributing to the Nominatim project and joining the OpenStreetMap Foundation. Open source and open data only thrive with an active, well-resourced community.
On our about page you can see a list of our efforts to support the community. Join us!