// function computes distance between two non-null points
// function computes distance using Haversine formula
static double getDistance(const GeographyPointValue &point1,
const GeographyPointValue &point2)
{
assert(!point1.isNull());
assert(!point2.isNull());
const S2LatLng latLng1 = S2LatLng(point1.toS2Point()).Normalized();
const S2LatLng latLng2 = S2LatLng(point2.toS2Point()).Normalized();
S1Angle distance = latLng1.GetDistance(latLng2);
return distance.radians() * SPHERICAL_EARTH_MEAN_RADIUS_M;
}
template<> NValue NValue::call<FUNC_VOLT_DISTANCE_POINT_POINT>(const std::vector<NValue>& arguments) {
assert(arguments[0].getValueType() == VALUE_TYPE_POINT);
assert(arguments[1].getValueType() == VALUE_TYPE_POINT);
if (arguments[0].isNull() || arguments[1].isNull()) {
return NValue::getNullValue(VALUE_TYPE_DOUBLE);
}
// compute distance using Haversine formula
// alternate to this is just obtain 2 s2points and compute S1Angle between them
// and use that as distance.
// S2 test uses S2LatLng for computing distances
const S2LatLng latLng1 = S2LatLng(arguments[0].getGeographyPointValue().toS2Point()).Normalized();
const S2LatLng latLng2 = S2LatLng(arguments[1].getGeographyPointValue().toS2Point()).Normalized();
S1Angle distance = latLng1.GetDistance(latLng2);
NValue retVal(VALUE_TYPE_DOUBLE);
// distance is in radians, so convert it to meters
retVal.getDouble() = distance.radians() * SPHERICAL_EARTH_MEAN_RADIUS_M;
return retVal;
}