FileMaker Pro Custom Functions

/*-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_ Custom Function DistanceGeoCoord -_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_ Abstract: DistanceGeoCoord ( Lat1deg ; Lat1mm ; Lat1ss ; Lon1deg ; Lon1mm ; Lon1ss ; Lat2deg ; Lat2mm ; Lat2ss ; Lon2deg ; Lon2mm ; Lon2ss ; U ; Version ) Developer: Edward Souza (edusouza@mac.com) Source: Custom Function DistanceGeoCoord is a FileMaker Pro 10 Advanced Custom Function based on formulae gathered from <http://mathforum.org/>. About this Custom Function: This is a rather complete function to measure the linear distance between two geographic coordinates in units such as Nautic Miles, Miles, Kilometers, and Meters. Because most Geographic Coordinates' calculae are based on a GIS standard known as Decimal Degrees (DD) -- and since coordinates themselves are expressed in a different format (DMS, or Degrees, Minutes, and Seconds) -- a conversion between them is necessary. This custom function does it, depending on how data are inserted in parameters Latitude 1 (Lat1deg, Lat1mm, and Lat1ss), Longitude 1 (Lon1deg, Lon1mm, and Lon1ss), Latitude 2 (Lat2deg, Lat2mm, and Lat2ss), and Logitude 2 (Lon2deg, Lon2mm, and Lon2ss). For example: if parameter Lat1deg has data inserted but Lat1mm and Lat1ss are left empty, the function will recognize the first as DD and treat it as such. The same will happen with the other coordinates. Thus you may mix both standards -- e.g. Coordinates 1 as DMS and Coordinates 2 as DD. This is quite handy if you are working with two databases, each based on a standard. According to SI and GIS, Northern and Eastern coordinates are understood as "positive", while Southern/Western ones are deemed as "negative". Hence, a set of coordinates such as S 9º48'40'' W 66º 53' 02'' shall be written as -9 48 40 and -66 53 02. Parameter "U" stands for "Unit", and accepts one of the following values: "Km" (for "Kilometers") "m" (for "meters") "Mi" (for "Miles") "NMi" (for "Nautical Miles"). Since these values refer to the radius of the earth at the equator, you may use any other. Just add them to the "R" variables. Parameter "Version" gives the function the ability to isolate or not the coordinates. One of these values -- Radians or Degrees -- shall be used. I hope you enjoy it. -_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_ Custom Function DistanceGeoCoord -_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_*/ Let ( [ //if latitudes and longitudes are not in Decimal Degrees (DD), these formulae will convert them to their decimal equivalencies Lat1Dec = If( not IsEmpty( Lat1mm ) and not IsEmpty( Lat1ss ); GetAsNumber( Lat1deg + GetAsNumber( Lat1mm / 60 ) + GetAsNumber( Lat1ss / 3600 ) ); GetAsNumber( Lat1deg ) ); Lon1Dec = If( not IsEmpty( Lon1mm ) and not IsEmpty( Lon1ss ); GetAsNumber( Lon1deg + GetAsNumber( Lon1mm / 60 ) + GetAsNumber( Lon1ss / 3600 ) ); GetAsNumber( Lon1deg ) ); Lat2Dec = If( not IsEmpty( Lat2mm ) and not IsEmpty( Lat2ss ); GetAsNumber( Lat2deg + GetAsNumber( Lat2mm / 60 ) + GetAsNumber( Lat2ss / 3600 ) ); GetAsNumber( Lat2deg ) ); Lon2Dec = If( not IsEmpty( Lon2mm ) and not IsEmpty( Lon2ss ); GetAsNumber( Lon2deg + GetAsNumber( Lon2mm / 60 ) + GetAsNumber( Lon2ss / 3600 ) ); GetAsNumber( Lon2deg ) ); //Version "Radian" Lat1Rad = Radians( Lat1Dec ); Lon1Rad = Radians( Lon1Dec ); Lat2Rad = Radians( Lat2Dec ); Lon2Rad = Radians( Lon2Dec ); dLonRad = Lon2Rad - Lon1Rad; ERad = Acos( ( Sin( Lat1Rad ) * Sin( Lat2Rad ) ) + ( Cos( Lat1Rad ) * Cos( Lat2Rad ) * Cos( dLonRad ) ) ); //Version "Degree" dLonDec = Lon2Dec - Lon1Dec; EDeg = Acos( ( Sin( Radians( Lat1Dec ) ) * Sin( Radians( Lat2Dec ) ) ) + ( Cos( Radians( Lat1Dec ) ) * Cos( Radians( Lat2Dec ) ) * Cos( Radians( dLonDec ) ) ) ) ; //Earth radius in several units (others may be added) R = Case( U = "Km"; 6378.137; // radius of the earth in kilometers U = "m"; 6378137; // radius of the earth in meters U = "Mi"; 3963.191; // radius of the earth in statute miles U = "NMi"; 3437.74677 // radius of the earth in nautical miles ) ]; Case( IsEmpty( Lat1deg ) or IsEmpty( Lon1deg ) or IsEmpty( Lat2deg ) or IsEmpty( Lon2deg ); "Error - Missing Geographic Data"; //If you added a new value, place its acronym here as well IsEmpty( U ) or ( U ≠ "Km" and U ≠ "m" and U ≠ "Mi" and U ≠ "NMi" ); "Error - Missing (or Wrong) Unit"; IsEmpty( Version ); "Error - Missing Version"; Version = "Degrees"; EDeg * R; Version = "Radians"; ERad * R ) )
 Then copy & paste into FileMaker Advanced's Edit Custom Function window.