Convert MapKit latitude and longitude to DMS format

Question

I am able to determine the latitude and longitude of a location in the center of a map with the following:

func TargetGridReference(outletMapView_PrimaryTargetLocationMap: MKMapView, regionDidChangeAnimated animated: Bool) {

    let ThreatGridReference = outletMapView_PrimaryTargetLocationMap.centerCoordinate

    let mapLatitude = String(format:"%.13f",ThreatGridReference.latitude)

    let mapLongitude = String(format:"%.13f",ThreatGridReference.longitude)
    let latAndLong = "Lat: \(mapLatitude) \nLong: \(mapLongitude)"

    self.outletLabel_TargetGridReference.text = latAndLong

    tempThreatGridReference = ThreatGridReference
    tempThreatGridReferenceLat = mapLatitude
    tempThreatGridReferenceLon = mapLongitude

}

This gives me the latitude for the Eiffel Tower in Paris as:

Lat:  48.8582487759147
Long:  2.2945180844931

How can I convert the above to the following DMS format in Swift?:

lat: 48° 51' 29.6956" N
long: 2° 17' 40.2651" E

Does MapKit provide automatic conversion into the various coordinate systems like UTM, UPS, MGRS, etc?

Answer 1

Unfortunately there is no automatic conversion but you can easily create one as follow:

Swift 4 or later

func coordinateToDMS(latitude: Double, longitude: Double) -> (latitude: String, longitude: String) {
    let latDegrees = abs(Int(latitude))
    let latMinutes = abs(Int((latitude * 3600).truncatingRemainder(dividingBy: 3600) / 60))
    let latSeconds = Double(abs((latitude * 3600).truncatingRemainder(dividingBy: 3600).truncatingRemainder(dividingBy: 60)))

    let lonDegrees = abs(Int(longitude))
    let lonMinutes = abs(Int((longitude * 3600).truncatingRemainder(dividingBy: 3600) / 60))
    let lonSeconds = Double(abs((longitude * 3600).truncatingRemainder(dividingBy: 3600).truncatingRemainder(dividingBy: 60) ))

    return (String(format:"%d° %d' %.4f\" %@", latDegrees, latMinutes, latSeconds, latitude >= 0 ? "N" : "S"),
            String(format:"%d° %d' %.4f\" %@", lonDegrees, lonMinutes, lonSeconds, longitude >= 0 ? "E" : "W"))
}

---

let dms = coordinateToDMS(latitude: 48.8582487759147, longitude: 2.2945180844931)

print(dms.latitude)  // "48° 51' 29.6956" N"
print(dms.longitude) // "2° 17' 40.2651" E"

You can also extend CLLocationCoordinate2D to get your latitude/longitude DMS description:

import MapKit
extension FloatingPoint {
    var minutes:  Self {
        return (self*3600)
            .truncatingRemainder(dividingBy: 3600)/60
    }
    var seconds:  Self {
        return (self*3600)
            .truncatingRemainder(dividingBy: 3600)
            .truncatingRemainder(dividingBy: 60)
    }
}
extension CLLocationCoordinate2D {
    var dms: (latitude: String, longitude: String) {
        return (String(format:"%d° %d' %.4f\" %@",
                       Int(abs(latitude)),
                       Int(abs(latitude.minutes)),
                       abs(latitude.seconds),
                       latitude >= 0 ? "N" : "S"),
                String(format:"%d° %d' %.4f\" %@",
                       Int(abs(longitude)),
                       Int(abs(longitude.minutes)),
                       abs(longitude.seconds),
                       longitude >= 0 ? "E" : "W"))
    }
}

---

let coord = CLLocationCoordinate2D(latitude: 48.8582487759147, longitude: 2.2945180844931)

coord.dms.latitude   // "48° 51' 29.6956" N"
coord.dms.longitude  // "2° 17' 40.2651" E"

Answer 2

I made some updates to this code to get it to work in Swift3 (mostly using .truncatingRemainder(dividingBy: ) rather than %) and also expanded it to output DMM as well, and included functions for converting DMM and DMS to DD!

extension CLLocationCoordinate2D {

    var latitudeMinutes:  Double { return (latitude * 3600).truncatingRemainder(dividingBy: 3600) / 60 }
    var latitudeSeconds:  Double { return ((latitude * 3600).truncatingRemainder(dividingBy: 3600)).truncatingRemainder(dividingBy: 60) }

    var longitudeMinutes: Double { return (longitude * 3600).truncatingRemainder(dividingBy: 3600) / 60 }
    var longitudeSeconds: Double { return ((longitude * 3600).truncatingRemainder(dividingBy: 3600)).truncatingRemainder(dividingBy: 60) }

    var dms:(latitude: String, longitude: String) {

        return (String(format:"%d°%d'%.1f\"%@",
                       Int(abs(latitude)),
                       Int(abs(latitudeMinutes)),
                       abs(latitudeSeconds),
                       latitude >= 0 ? "N" : "S"),
                String(format:"%d°%d'%.1f\"%@",
                       Int(abs(longitude)),
                       Int(abs(longitudeMinutes)),
                       abs(longitudeSeconds),
                       longitude >= 0 ? "E" : "W"))
    }

    var dmm: (latitude: String, longitude: String) {
        return (String(format:"%d°%.4f'%@",
                      Int(abs(latitude)),
                      abs(latitudeMinutes),
                      latitude >= 0 ? "N" : "S"),
               String(format:"%d°%.4f'%@",
                      Int(abs(longitude)),
                      abs(longitudeMinutes),
                      longitude >= 0 ? "E" : "W"))
    }
}

var coord = CLLocationCoordinate2D(latitude: 41.40338, longitude: 2.17403)

coord.latitude // 41.40338
coord.longitude // 2.17403
coord.latitudeMinutes // 24.20280000000009
coord.latitudeSeconds // 12.16800000000512
coord.longitudeMinutes // 10.44180000000001
coord.longitudeSeconds // 26.50800000000072

coord.dms.latitude   // "41°24'12.2"N"
coord.dms.longitude  // "2°10'26.5"E"
coord.dmm.latitude   // "41°24.2028'N"
coord.dmm.longitude  // "2°10.4418'E"

These conversion functions also allow an input without indicating cardinal direction, but rather just supplying positive or negative:

func DMStoDD(latDeg: Double, latMin: Double, latSec: Double, latDir: String?, longDeg: Double, longMin: Double, longSec: Double, longDir: String?) -> CLLocationCoordinate2D {
    var latitude = CLLocationDegrees()
    if latDeg > 0 {
        latitude = CLLocationDegrees(latDeg + ((latMin*60)/3600) + (latSec/3600))
        if latDir == "S" {latitude *= -1}
    }
    else{
        latitude = CLLocationDegrees((latDeg * -1) + ((latMin*60)/3600) + (latSec/3600))
        latitude *= -1
    }

    var longitude = CLLocationDegrees()
    if longDeg > 0 {
        longitude = CLLocationDegrees(longDeg + ((longMin*60)/3600) + (longSec/3600))
        if longDir == "W" {longitude *= -1}
    }
    else{
        longitude = CLLocationDegrees((longDeg * -1) + ((longMin*60)/3600) + (longSec/3600))
        longitude *= -1
    }
    return CLLocationCoordinate2D(latitude: latitude, longitude: longitude)
}

coord = DMStoDD(latDeg: 41, latMin: 24, latSec: 12.2, latDir: "", longDeg: 2, longMin: 10, longSec: 26.5, longDir: "")
coord.latitude // 41.40338888888889
coord.longitude // 2.174027777777777

And DMM to DD

func DMMtoDD(latDeg: Double, latMin: Double, latDir: String?, longDeg: Double, longMin: Double, longDir: String?) -> CLLocationCoordinate2D {
    var latitude = CLLocationDegrees()
    if latDeg > 0 {
        latitude = CLLocationDegrees(latDeg + ((latMin*60)/3600))
        if latDir == "S" {latitude *= -1}
    }
    else{
        latitude = CLLocationDegrees((latDeg * -1) + ((latMin*60)/3600))
        latitude *= -1
    }
    var longitude = CLLocationDegrees()
    if longDeg > 0 {
        longitude = CLLocationDegrees(longDeg + ((longMin*60)/3600))
        if longDir == "W" {longitude *= -1}
    }
    else{
        longitude = CLLocationDegrees((longDeg * -1) + ((longMin*60)/3600))
        longitude *= -1
    }
    return CLLocationCoordinate2D(latitude: latitude, longitude: longitude)
}

coord = DMMtoDD(latDeg: 41, latMin: 24.2028, latDir: "N", longDeg: 2, longMin: 10.4418, longDir: "E")
coord.latitude // 41.40338
coord.longitude // 41.40338