The Impact of Secondary Address Designators on Coordinates

Geocoding, along with converting the latitude and longitude of a physical address, is becoming inseparable from our daily lives. Conversely, without the use of latitude and longitude coordinates, the online industry will collapse. Passing the address and expecting to obtain exact geolocation in return sounds like an easy assignment. However, not every batch geocoder is designed to handle the function properly. For example, consider the inclusion of the secondary unit designators typically attached to an address. The secondary unit designators represent additional information designed to guide the user in finding the address. Examples of such designators are:

The list of designators can continue indefinitely.

Understanding the Role of Secondary Address Units

To help the users understand how a secondary address unit designator affects geocoders, we will select a random address, such as 199 WATER ST # LBBY NEW YORK NY. First, we will try to insert the address into Google Maps to observe the coordinates the app will appoint to it.

The result that comes back is 40.7069416,-74.0065382,17.

secondary unit

Secondly, we will eliminate the secondary address unit, leaving the address to 199 WATER St. NEW YORK NY.


The result that comes back is 40.7068749,-74.0049329.

results from secondary unit

As the user can notice from the two images demonstrated above, the map with latitude and longitude diverges depending on the use of a secondary address unit designator.


The Impact of Secondary Address Units on Coordinates


In batch geocoding, it is presumed that more than one address is set for the convening of latitude and longitude. If the user is interested in the larger picture, ignoring the accuracy of the calculations of physical location, adding the secondary designator can complicate the structure, leading batch geocoders to return confusing data. Moreover, a geocoder can return multiple addresses. Unfortunately, the indicated problem is frequent, as the apps try to be intelligent and present outstanding data for the users. Nevertheless, they in fact move away from the accuracy, providing the end user with a large number of choices.   


As can be seen in the examples above, when we used the secondary unit designator, Google Maps returned more than one result, but the first one was considered more accurate.


If we apply the golden rule of 80/20, we can state that in 80% of the cases, two-dimensional coordinates work well with the exception of secondary address unit designators. In that case, the end user is more interested in receiving the general address, and not the exact GPS coordinates.


On the other hand, providing a secondary address unit designator may be necessary, although in rare cases. In the majority of batch geocoders, it is not specified whether the user can turn on or off the use of secondary designators. The program’s design is set, and the user must pay attention to the use of designators when repairing the input file.


As an example, consider this address entered into Google Maps:

250 W 34TH ST # 3600 NEW YORK NY 10119


The secondary designator in this address is # 3600.


The geolocation is 40.7511802,-73.9937387.

geolocation map secondary address

Now, consider the same address without the designator:

250 W 34TH ST # 3600 NEW YORK NY 10119


It returns 40.7511802,-73.9937387.

lat long results

As the examples above show, the two addresses are absolutely identical since the geolocation was done in 2D, with the altitude excluded.


In general, try to use 2D geolocation first, without including the second address unit designator, when preparing batch geocoding process data. An excellent tool for the task is CSV2GEO. It comes with free batch geocoding and is an inexpensive paid option for processing large amounts of data.