Area search
The radius search is an option of various online services to limit the search results to the radius of a geographic location. The option is offered, for example, by ad databases and online auctions and is usually based on the postal code .
Proximity search principles
The postcode is often used to determine the geographical location, as this is usually known to searchers and providers, unlike geographic coordinates , and, unlike the postal address, is quick to enter. The assignment of a postcode to geographic coordinates ( longitude and latitude ) is done with the help of a corresponding database or a web service .
The objects to be found must also be provided with coordinates. This can be done by manually entering length and width or, as above, with the help of a database or web service roughly using the zip code or using the complete postal address.
With the help of the spherical geometry , the shortest path (the orthodromes ) between the location and the object location can be calculated. Alternatively, a distance table can be generated for all postcodes and objects using the same procedure . The determined distances can then be used to filter and sort according to user requirements.
A partial possibility is based on the assumption that the proximity of two postcodes is related to the correspondence of the first digits. In many cases this is correct, but incomplete. For example, 95188 borders on 95180 , which is very likely due to the zip code, but the zip codes for 07366 , which is also adjacent, are not similar. The process is therefore rarely used. The exact procedure describes an imprecise search for the vicinity .
