Rounding Error when converting double values from TextField to Coordinates for MapItemView

SgtSherif

I'm trying to add coordinates on a map in QML and then pass it to C++ to eventually send to a drone. I'm using a ListModel to store the coordinates but I'm having problems with the accuracy of the waypoint.

ListModel {
    id:wpModel
}

Plugin {
    id: mapPlugin
    name: "mapboxgl"
 }

The map is setup in QML like this

Map{
        id: map
        anchors.fill:parent
        plugin: mapPlugin
        center: QtPositioning.coordinate(48.854314, 2.292297)
        zoomLevel:18
        copyrightsVisible: false
        tilt: 45

        MapItemView{
            model:wpModel
            delegate:MapQuickItem{
                coordinate{
                    latitude: lat
                    longitude: lon
                } 
                sourceItem: Image{
                    id:waypointMarker
                    opacity: .75
                    sourceSize.width:80
                    sourceSize.height:80
                    source: "qrc:///marker-red.png"
                }  
            anchorPoint.x: waypointMarker.width/2
            anchorPoint.y: waypointMarker.height

            }
        }

    }

I then have two textfields with a DoubleValidator for the Latitude and Longitude of the waypoint.

RowLayout{
     Label{
     text: "Start Lat:"
      } 
     TextField{
        id: startLatInput
        validator:DoubleValidator{
             decimals:15
             notation:DoubleValidator.ScientificNotation
        }
     }
     Label{
       text:"Start Lon:"
     }
     TextField{
        id: startLonInput
        validator:DoubleValidator{
        decimals:15
        notation:DoubleValidator.ScientificNotation
        }
      }  
  } //RowLayout

And finally a button which appends the waypoint to the model

  Button{
     id: wpOkButton
     text: "OK"
     onClicked:{
        var startLat = parseFloat(startLatInput.text)
        var startLon = parseFloat(startLonInput.text)
        var val = map.toCoordinate(startLat, startLon)
        wpModel.append({lat: startLatInput.text, lon: startLonInput.text})                                                         
        }
   } // okButton

The parsing of the startLon and startLat returns the same value as startLatInput.text and startLonInput.text but once I append to wpModel, the value changes and is completely different to my input. This is what an example output looks like:

If we take, the following coordinate 52.756105, -1.247304 which is at the edge of the field on google maps and the output for MapQuickItem becomes

qml: 52.75859356721886
qml: -1.2512258791688566

which is metres away from the intended waypoint. The same behaviour is found if I just hardcode the coordinates into a MapQuickItem i.e.

MapQuickItem{
        sourceItem: Image{
            id:sample
            opacity: .75
            sourceSize.width:80
            sourceSize.height:80
            source: "qrc:///marker-red.png"
        }
        coordinate: QtPositioning.coordinate(52.756105, -1.247304)
        anchorPoint.x: sample.width/20
        anchorPoint.y: sample.height

    }

However, if I physically click on the waypoint I want using a mouse, I get what I or close to it anyway,

MouseArea{
  anchors.fill:parent
  focus:true
  hoverEnabled:false
  acceptedButtons: Qt.LeftButton

      onPressAndHold: {
             var pos = map.toCoordinate(Qt.point(mouse.x,mouse.y));                 
             console.log(pos.latitude)
             console.log(pos.longitude)  
      }

  }

This returns an output of

qml: 52.75604121576361
qml: -1.247375123866334

which is kind of acceptable.

Can someone please elaborate on what I'm doing wrong here?