/// <summary>
/// Returns Entities according to a distance calculation and includes the computed distance in the result.
/// </summary>
/// <param name="query">The Query to perform the filter on.</param>
/// <param name="originLatitude">Origin Latitude to calculate distance against.</param>
/// <param name="originLongitude">Origin Longitude to calculate distance against.</param>
/// <param name="entityLongitudeAttributeName">Attribute name on target entity.</param>
/// <param name="entityLatitudeAttributeName">Attribute name on target entity.</param>
/// <param name="maxDistance">Maximum distance from point of origin to location.</param>
/// <param name="units">Unit of measure (Kilometers or Miles)</param>
public static IEnumerable <Tuple <Entity, double> > DistanceQueryWithResult(this IEnumerable <Entity> query, double originLatitude, double originLongitude,
string entityLongitudeAttributeName, string entityLatitudeAttributeName, int maxDistance, GeoHelpers.Units units)
{
//http://en.wikipedia.org/wiki/Spherical_law_of_cosines
// Distance = acos(SIN(lat1)*SIN(lat2)+COS(lat1)*COS(lat2)*COS(lon2-lon1))*6371
//convert degrees to radians - multiply degrees by p/180
var earthRadius = units == GeoHelpers.Units.Kilometers
? GeoHelpers.EarthRadiusInKilometers
: GeoHelpers.EarthRadiusInMiles;
var returnEnumerable = from c in query
let latitude = c.GetAttributeValue <double>(entityLatitudeAttributeName)
let longitude = c.GetAttributeValue <double>(entityLongitudeAttributeName)
let distance =
earthRadius * 2 *
Math.Asin(
Math.Sqrt(Math.Pow(Math.Sin((Math.Abs(originLatitude) - Math.Abs(latitude)) * Math.PI / 180 / 2), 2) +
Math.Cos(Math.Abs(originLatitude) * Math.PI / 180) * Math.Cos(Math.Abs(latitude) * Math.PI / 180) *
Math.Pow(Math.Sin((Math.Abs(originLongitude) - Math.Abs(longitude)) * Math.PI / 180 / 2), 2)))
where distance < maxDistance
orderby distance
select new Tuple <Entity, double>(c, distance);
return(returnEnumerable);
}
/// <summary>
/// Filter by comparison of origin latitude and longitude coordinates against the bounding box coordinates.
/// </summary>
/// <param name="fetch">Entity fetch.</param>
/// <param name="originLatitude">Origin Latitude to calculate distance against.</param>
/// <param name="originLongitude">Origin Longitude to calculate distance against.</param>
/// <param name="entityLongitudeAttributeName">Longitude attribute name on target entity.</param>
/// <param name="entityLatitudeAttributeName">Latitude attribute name on target entity.</param>
/// <param name="entityLongLatAttributeType">Attribute type either 'double' or 'decimal'.</param>
/// <param name="distance">Maximum distance from point of origin to location.</param>
/// <param name="units">Unit of measure (Kilometers or Miles).</param>
/// <returns></returns>
public static Fetch FilterByBoxDistance(this Fetch fetch, double originLatitude, double originLongitude,
string entityLongitudeAttributeName, string entityLatitudeAttributeName,
string entityLongLatAttributeType, int distance, GeoHelpers.Units units)
{
//get the bounding box
var earthRadius = units == GeoHelpers.Units.Kilometers ? GeoHelpers.EarthRadiusInKilometers : GeoHelpers.EarthRadiusInMiles;
var angularDistance = distance / (double)earthRadius; // angular distance on a great circle
var originLatitudeRadians = GeoHelpers.DegreesToRadians(originLatitude);
var originLongitudeRadians = GeoHelpers.DegreesToRadians(originLongitude);
var minLatitudeRadians = originLatitudeRadians - angularDistance;
var maxLatitudeRadians = originLatitudeRadians + angularDistance;
var deltaLongitude = Math.Asin(Math.Sin(angularDistance) / Math.Cos(originLatitudeRadians));
var minLongitudeRadians = originLongitudeRadians - deltaLongitude;
var maxLongitudeRadians = originLongitudeRadians + deltaLongitude;
var minLatitude = GeoHelpers.RadiansToDegrees(minLatitudeRadians);
var maxLatitude = GeoHelpers.RadiansToDegrees(maxLatitudeRadians);
var minLongitude = GeoHelpers.RadiansToDegrees(minLongitudeRadians);
var maxLongitude = GeoHelpers.RadiansToDegrees(maxLongitudeRadians);
if (entityLongLatAttributeType.ToLower() == "double")
{
fetch.Entity.Filters.Add(new Filter
{
Conditions = new[]
{
new Condition(entityLatitudeAttributeName, ConditionOperator.GreaterThan, minLatitude),
new Condition(entityLatitudeAttributeName, ConditionOperator.LessThan, maxLatitude),
new Condition(entityLongitudeAttributeName, ConditionOperator.LessThan, maxLongitude),
new Condition(entityLongitudeAttributeName, ConditionOperator.GreaterThan, minLongitude)
},
Type = LogicalOperator.And
});
}
else if (entityLongLatAttributeType.ToLower() == "decimal")
{
fetch.Entity.Filters.Add(new Filter
{
Conditions = new[]
{
new Condition(entityLatitudeAttributeName, ConditionOperator.GreaterThan, (decimal)minLatitude),
new Condition(entityLatitudeAttributeName, ConditionOperator.LessThan, (decimal)maxLatitude),
new Condition(entityLongitudeAttributeName, ConditionOperator.LessThan, (decimal)maxLongitude),
new Condition(entityLongitudeAttributeName, ConditionOperator.GreaterThan, (decimal)minLongitude)
},
Type = LogicalOperator.And
});
}
return(fetch);
}
