关于Google Places API小半径返回更多POI及相关机制的技术咨询

Great observation about the noticeable difference in POI counts when using a 50m vs 200m radius with the Google Places API—let’s break down your two questions with clear technical context:

The term "bias" here refers to result ranking priority, not strict geographic filtering. When you set a radius parameter:

• The API will prioritize returning places that fall within the specified distance from your central coordinates. These places will appear higher in the results list.
• However, it doesn’t completely exclude places outside the radius. Well-known, prominent locations (like major landmarks, large chain stores, or popular tourist spots) that are slightly outside the radius may still show up in results, especially if they’re relevant to your search query.

To quote the official API documentation directly:

radius——定义用于对地点结果进行偏向性筛选的距离（单位：米），最大允许半径为50000米。该区域内的结果排名高于搜索圈外结果，但也可能包含搜索半径外的知名地点。

In practical terms, if you search for "cafes" with a 50m radius, a tiny local cafe 30m away will rank higher than a famous national chain cafe 150m away—but the chain cafe might still appear lower in the results because of its prominence.

There’s no strict, one-to-one mapping between API radius values and Google Maps zoom levels, because:

• Zoom levels are based on the map’s visual viewport (which depends on screen size and latitude, due to the Mercator projection), while the API’s radius is an absolute geographic distance.
• Zoom levels adjust the area visible on the map, not a fixed search radius.

That said, here’s a rough, practical correspondence you can use as a reference (based on typical desktop/mobile map views):

• Zoom level 18: ~20–50m radius (street-level detail, shows individual buildings and small local spots)
• Zoom level 17: ~100–200m radius (covers a few blocks)
• Zoom level 16: ~400–800m radius (covers a larger neighborhood section)
• Zoom level 15: ~800–1600m radius (covers most of a small neighborhood)
• Zoom level 14: ~1.6–3.2km radius (covers a large part of a city district)

Keep in mind these are approximate—latitude affects the actual geographic area covered by a zoom level (areas near the poles cover less ground than equatorial regions at the same zoom). If you’re building an app that ties map zoom to Places API searches, you’ll want to test these ranges with your target user locations to get the best results.

内容的提问来源于stack exchange，提问作者Shashank Golla