Questions · Addresses

How do I get the coordinates of an address?

Why normalization comes first, and geocoding after

A geocoding service always answers with a point, even for a wrong address: it takes the street that looks most alike and puts a dot on it. If the address had the postcode of another city or the street abbreviated in an ambiguous way, the point is convincing and wrong, and nobody notices until the courier calls.

RadarAddress does the opposite: first the address verification, which resolves city, street and house number with the same declared outcomes as normalization, then the lookup of the coordinates on the address already corrected. If the street is not found in the municipality, there is no point: the outcome says the address needs a look, and the coordinate stays empty instead of being invented.

The levels of precision, always declared

The coordinates come with a field that says at what level they were found:

• house number: the point of the house number itself, taken from the national register. In the Netherlands, where the register georeferences every address, this is the normal case.
• interpolated: the exact number is not georeferenced, and the point is estimated from the neighbouring numbers on the same street. Fine for a map or for calculating distances, not for a delivery to the metre.
• street: only the point of the street, when nothing is known about the house numbers.
• municipality: only the centre of the municipality. It is the last resort, useful for grouping, not for locating.

Coverage changes from country to country and, within a country, from municipality to municipality: in some registers it is complete, in others whole districts are missing, and in countries without a register in service the point comes from open map data. This is why the level is written next to every point and there is no single coverage figure to promise: you look at the field and decide what to do with it.

Along with the coordinates: the municipality code

With the address resolved comes the identifier of the municipality in the national register, the one you need to link your database to other databases without going through the name written by hand. It is data your file did not have, and it lets you, for example, count customers by municipality with a join instead of a text search, or attach public statistics by municipality to your own records.

What georeferencing a database is for

Coordinates turn a list of addresses into a map you can reason on. The most common uses:

• Assigning contacts to a territory. Every record ends up in the area of a sales agent, a branch, a volunteer or a delegate, by real proximity and not by postcode, which in the big cities cuts neighbourhoods in half.
• Calculating distances. How far each customer is from the nearest shop, how many supporters live within ten kilometres of the venue of an event, which addresses are worth grouping in a delivery round.
• Seeing where the customers are. A map of donors, orders or members shows at a glance where the work pays and where it is missing, better than a table by region.
• Crossing external data. With the municipality code you attach population, density and all the public statistics by municipality, without going through the name written by hand.
• Recognizing neighbouring addresses. Two records with different streets and the same point on the map deserve a look: it happens with renamed streets and with the double entrances of the same building.

In all these cases the level of precision matters: to assign a territory the municipality is enough, for a delivery round you need the house number. That is why it always comes out written next to the point.

Where you find them: site, file, API

In the verification from the site, when the address is resolved, the coordinates appear with their level. In a job from a file the columns latitude, longitude and geo_precision are added to the result for every row, next to the municipality code: geocoding a whole database in bulk is the same job as the verification, not a separate service. In the API the endpoint /api/v1/contact returns the geo object with latitude, longitude, precision and source, and the territory object with the codes; the documentation lists the fields and the attribution due when the source is open map data.

The price is that of the address verification: coordinates and codes are part of the result. The price list is on the pricing page.

An address, the point and its level

The postcode has been written in the Dutch form and confirmed for that house number, the city put in capitals. The point is the one of house number 1 in the national register, and the precision field says so.