Reduce distance range again, because ti doesn't appear to be working right.

common/Normalisers.mjs

@@ -32,7 +32,7 @@ function unnormalise_lng(nlng) {
 
 function normalise_gateway_distance(distance) {
 	return clamp(normalise(distance,
-		{ min: 0, max: 75000 },
+		{ min: 0, max: 20000 },
 		{ min: 0, max: 1 }
 	), 0, 1);
 }
@@ -40,7 +40,7 @@ function normalise_gateway_distance(distance) {
 function unnormalise_gateway_distance(ndistance) {
 	return normalise(ndistance,
 		{ min: 0, max: 1 },
-		{ min: 0, max: 75000 }
+		{ min: 0, max: 20000 }
 	);
 }