How to retrieve nearest data from mysql using GPS coordinates? [duplicate] - php

Question

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PHP MySql and geolocation
(3 answers)
Closed 9 years ago.
I am using this SQL query to get data that is nearest to GPS coordinates.
SELECT geo_latitude, geo_longitude, geo_name, geo_country_code AS country,
(DEGREES(
ACOS(
SIN(RADIANS(47.470779)) * SIN(RADIANS(geo_latitude)) +
COS(RADIANS(47.470779)) * COS(RADIANS(geo_latitude)) *
COS(RADIANS(-87.890699 - geo_longitude))
)
) * 60 * 1.1515)
AS distance FROM `MyDatabase`.`allCountries` ORDER BY distance ASC LIMIT 20 ;
This query retrieves all the data irrespective of the distance. I would like it to display the data only within a radius of 10 miles. How can i achieve this?

Answer 1

There's two ways I've found. One way is to do a direct SQL query with a whole lot of math in the 'where' section, much like you've tagged for your AS distance section of the SQL. Essentially - conceptually - 'where distance < 10'
However, I've found that slows down my request ... so what I've done in addition is to pull out the square instead of the circle from the database. Simply put: figure out the 'ten miles west/north/east/south' coords, then put in WHERE geo_latitude < X1 AND geo_latitude > x2 AND geo_longitude < x3 AND geo_longitude > x4 to put a hard limit on what I get back. Then, if you really need to be that precise, cut off the corners by only displaying if( result.distance < 10 ){
Or to put it another way:
x1 = Coords + 10 miles north
x2 = Coords + 10 miles south
x3 = Coords + 10 miles east
x4 = Coords + 10 miles west
by whatever means you're using to indicate '10 miles north', and then use that to pull out a 'square' of 10-miles north, south, west, and east from the center point. As long as your geo_latitude and geo_longitude columns are indexed, this should be a fast database call.