MBR Within not accurate in mysql

问题

I have been using the MBRWithin function for quite a lot of times. Suddenly I notice on google map this POINT(101.11857 4.34475) is out of the geo fence which I specify but it still give a value of 1 in mysql any reason or tweaking need to be done?

SELECT MBRWithin(GeomFromText('POINT(101.11857 4.34475)'),GeomFromText('POLYGON((101.12112522125244 4.3531723687957164,101.11846446990967 4.351417913665312,101.13138198852539 4.336397898951581,101.13477230072021 4.33211863778494,101.14065170288086 4.321933898868271,101.14992141723633 4.306699328215635,101.15455627441406 4.30978050198082,101.1397933959961 4.334600612212089,101.12112522125244 4.3531723687957164,101.12112522125244 4.3531723687957164))')) As geoFenceStatus

回答1:

MySQL 5.6.1 and later have exact geometry algorithms in addition to the earlier functions that only operated on MBR.

You can use ST_WITHIN rather than MBR_WITHIN. See documentation. Like this

SELECT ST_Within(GeomFromText('POINT(101.11857 4.34475)'),
  GeomFromText('POLYGON((101.12112522125244 4.3531723687957164,101.11846446990967 
    4.351417913665312,101.13138198852539 4.336397898951581,101.13477230072021 
    4.33211863778494,101.14065170288086 4.321933898868271,101.14992141723633 
    4.306699328215635,101.15455627441406 4.30978050198082,101.1397933959961 
    4.334600612212089,101.12112522125244 4.3531723687957164,101.12112522125244 
    4.3531723687957164))')) As geoFenceStatus

回答2:

MBRWithin() will return results based on the minimum bounding rectangle of it's parameters. Your polygon contains both larger and smaller values for both coordinates than the point, so it will be within the polygon's MBR.

MySQL has no built-in point in polygon algorithm, so you'll either have to roll your own or find one elsewhere. This one seems to be a good candidate.

来源：https://stackoverflow.com/questions/7782873/mbr-within-not-accurate-in-mysql