only sync pois nearby current location in google maps

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I want my application to synchronize only the poi locations in the neigbourhood of mij current location. I think this can be realised bij a xpath constraint but do not know how to do this exactly. De POI logitude en latitude are in the entity "pois". In another antity "location" i have te longitude en latitude of the current location. Please help me wit the xpath constraint.
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1 answers
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There are a number of ways to calculate distance between 2 sets of coordinates, but the lightest weight (and reasonably accurate) calculation for short distances is the Pythagorean theorem.

I don't think there's a way to write this in XPath. You would need to run a distance calculation between your location and every point in your database, which could be very slow depending on the number of rows you're searching.

Here's another thread I found on the matter. Based on this, here's how I would approach the issue:

  1. Find the upper and lower bounds for the latitude and longitude of your current location and radius. This will effectively give you a rectangular area around your current location
  2. Write your XPath to get all POIs inside that rectangle
  3. For each POI returned, run a distance calculation between that point and your current location. If it's within the radius, keep it. If not, remove it from the POI list.
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