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Ask HN: Efficient API to calculate distances?

2 points by RDDavies ↗ HN
Google maps seems rather slow for this.

For ~200 displayed fields, need to calculate distance (by road) between a user-input zip and various other zips. Suggestions?

The project in question is finding autocross events within x miles of a user-entered zip, hence the need to do this dynamically, rather than store the data.

1 comment

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byoung2
You can trade some accuracy for speed by calculating the straight-line distance and then increasing it by some factor to account for turns and detours. Converting zip codes to latitude/longitude is a trivial process if you have a database (e.g. MaxMind) or API (e.g. SimpleGeo). You can calculate straight-line distance between two lat/lon pairs pretty easily (http://jan.ucc.nau.edu/~cvm/latlon_formula.html), and then pad this number to account for geography (e.g. 20 miles as the crow flies is ~27 miles driving).

If you can sacrifice even more accuracy, you can use 50-70 miles per degree latitude/longitude and just find results within a certain range of a given lat/lon pair.