# Create conditions "GPS from the device matches the predefined coordinates"

Hello,
I am a complete layman and beginner. I would like to set the condition on the button, so that the next page opens after clicking, if the condition is met: the GPS signal from the device will match the pre-entered coordinates. For a better explanation, I give an example: I have to find the specified place in the terrain according to the indications. When I think I found it, I press the button “I’m here” and if the current position matches the one entered, the next page in the app will open.

first I have to say that unfortunately, the GPS functions on Android are not working well yet but I really hope this is fixed at some point.
Assuming that the GPS functions are working (e.g. Get GPS Position function from marketplace), you best create a custom Javascript function which calculates the distance to a predefined GPS coordinate like this:
lat1 = inputs[“lat1”];
lon1 = inputs[“lon1”];
lat2 = inputs[“lat2”];
lon2 = inputs[“lon2”];
unit=“K”;

if ((lat1 == lat2) && (lon1 == lon2)) {
return { result:0 };
}
else {
var radlat1 = Math.PI * lat1/180;
var radlat2 = Math.PI * lat2/180;
var theta = lon1-lon2;
var radtheta = Math.PI * theta/180;
if (dist > 1) {
dist = 1;
}
dist = Math.acos(dist);
dist = dist * 180/Math.PI;
dist = dist * 60 * 1.1515 * 1000;
if (unit==“K”) { dist = dist * 1.609344 }
if (unit==“N”) { dist = dist * 0.8684 }
return { result:dist };
}

If you have a couple of coordinates to check against, you need to pass the list in.

Hope this helps a bit.

Best,
Jo