Geographical ranking precision
Precision (using the search query parameter aroundPrecision) is used to group results that have more or less the same distance from a central point.
Algolia’s default precision is 10 meters. However, a 10-meter difference might not be significant: intervals of 200 meters may make more sense. By creating 200-meter intervals, you rank all records that fall within that interval the same. They’re ranked higher than all records between 200 and 400 meters.
If you set aroundPrecision to 200, you’ll have the following search results:
- Group of results in the 0-200 meters range will be the best ranked (ranked equally)
- Group of results in the 200-400 meters range will be ranked a bit lower
- Group of results in the 400-600 meters range will be ranked even lower
Another example is when users are looking for nearby recommended restaurants. The goal is to display results that are a good mix of nearby and highly rated restaurants.
If there are two restaurants within 200 meters of a user’s location:
- Restaurant A with a 5 star rating and distance of 150 meters (farther)
- Restaurant B with a 3 star rating and distance of 100 meters (closer)
If you’re only sorting by geographical distance, restaurant B will be ranked higher since it’s closer to the user.
But by setting aroundPrecision to 200, restaurant A and B will be ranked equally: the distances of 150 and 100 will be considered equal to 0 (and distances of 250 and 210 will be equal to 200, and so on).
Going further, since the results of A and B are tied under the Geo criterion, the search engine will examine the other criteria in the ranking formula to further sort the results. Restaurant A will therefore be ranked higher in the result due to its higher rating.
