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I have function that takes a users coordinates and tests it against a polygon. When I create the fence with whole numbers such as [3,2], [3,4],[5,6],[3,2]. My function returns correctly. I tried inputting real data to create a geofence and used the chrome devtools to simulate a custom geolocation that was within the geofence. However, with real coordinates ( 40.225928, -111.660785) it does not return that the point is within the polygon. Below is my object and method.

const fence = {Fence1: turf.polygon([
  [[40.225,-111.658], [40.2229,-111.664], 
  [40.223,-111.667], [40.225,-111.668], 
  [ 40.226,-111.666], [40.225,-111.658]]
 ])    
};

module.exports = {
check_fences: (req,res,next) => {
    var pt1 = turf.point([req.body.latitude, req.body.longitude]);

for (key in fences) {
  if(turf.intersect(pt1, fences[key])) {
   console.log(key)
   fence = key
 }
}
 if(resort) {
    return res.status(200).send(resort)
} else {
    return res.status(200).send('NOT IN FENCE')
}

The req body object is coming in as: { latitude: 40.224411, longitude: -111.66478 }

Developing with ReactJS

I am at a loss for why this is not working.

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I don't think your point is intersecting with the polygon.

enter image description here

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  • So I just realized that again, my coordinates were flipped. So I switched the latitude to the first digits and now it is working! Ha whoops!
    – Sharkboots
    Dec 7, 2017 at 22:40
  • I do have another question going off of this. I've tried using the plugin for QGIS and I can't seem to get it to work. I put in: POLYGON (( -111.665784 40.229448, -111.653481 40.229554, -111.653481 40.229554, -111.665784 40.229448)) and then my Point coordinates but I only saw the points. Do I need anything different or do I need to pick one of the specific POLYGON options in the dropdown.Also, I hope that the switched coordinates would have fixed the issue on your end too since I'm getting back true for this query!
    – Sharkboots
    Dec 7, 2017 at 22:44
  • For other people, I think you mean the "QuickWKT" plugin? I think that polygon is poorly defined, it comes up as almost a line here. Do you add in the polygon in one entry and the point in a second entry?
    – Lennert De Feyter
    Dec 7, 2017 at 22:48
  • Would that explain why it comes in as true sometimes but not always. I'm manually changing the locations in small increments and doesn't seem to be constantly reading accurately. I am not sure if there is a better method of mapping out polygon coordinates. I'm using google maps to just find some points to turn into a polygon. I did 2 in one POLYGON (( -111.665784 40.229448, -111.653481 40.229554, -111.653481 40.229554, -111.665784 40.229448)) POINT (-111.660785 40.225928)
    – Sharkboots
    Dec 7, 2017 at 22:53
  • You can just draw the polygon in qgis and get the wkt values from there?
    – Lennert De Feyter
    Dec 8, 2017 at 2:19

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