问题
I am trying to get traffic flow data for a 100m proximity in Thessaloniki Greece. Specifically I send the request below:
https://traffic.api.here.com/traffic/6.1/flow.json?prox=40.63373%2C22.94515%2C100&app_id=devportal-demo-20180625&app_code=9v2BkviRwi9Ot26kp2IysQ
The returned json object contains road segments far outside this area. In fact it seems that even if I change the proximity radius or it's center within the city, I always get the same object as a response which seems to be consisted of some main roads inside the city.
Any idea why this is happening? I mean if there were no data for my proximity I would expect maybe an empty object as a response.
回答1:
API is giving correct response however the problem is, that even if you can specify 1 or 100 meters as radius the service really support only the smallest resolution of 1 km. This is due to how the data is stored in the service, which is tile based.
and each such a request is then converted to tiles - which have a predefined size. So a 100 meters request can end up in a tile of size 1x1 km easily. That is why you get traffic outside of a smaller proximity.
来源：https://stackoverflow.com/questions/58893652/traffic-flow-request-in-here-api-returns-results-outside-of-the-proximity