Different GeoPosition values for OnTouch and OnClick

[JACochran]

Email received:

In our pluggable map MapClickedListener there are 2 methods that are called when clicking on the map. The first is an onTouch listener that will respond to the first touch of the screen regardless of event type (singe, double, long, drag, etc). This means this method is always called when the map is clicked. In the case of long press onTouch is called followed by the MapUserInteractionEvent. I took data on a single click with the mouse pointer and then on the same location a long press. Here is an example of the results.

A single click from the on touch method
On Touch: LatLonPoint[lat=34.765178249375595,lon=-86.41371591023108]
On Touch x,y: Point(815, 189)
on Event Single Press: LatLonPoint[lat=34.76517061862333,lon=-86.41370651566413]

A long press
On Touch: LatLonPoint[lat=34.69682246526478,lon=-86.56669172935936]
MapClickedListener: On Touch x,y: Point(624, 287)
on Event Long Press: LatLonPoint[lat=34.69638638712407,lon=-86.56609375423172]
On Long Press x,y: Point(624, 287)

On Touch: LatLonPoint[lat=34.765178249375595,lon=-86.41371591023108]
On Touch x,y: Point(815, 189)
on Event Long Press: LatLonPoint[lat=34.76517061862333,lon=-86.41370651566413]
On Long Press x,y: Point(815, 189)

Distance between touch and long press: 1.2068360080193425

Included at the end is the distance in meters of how far apart these locations are. Zooming out give a larger error and zooming in averaged about .1 m in distance between touch and long press.

I also tried a few times starting around the equator and long pressing further away. Distance between the onTouch calculation and the long press varried any where from about 1200m to 3800m with no relation to how far from the equator I was. This was zoomed way out to see large changes in the data set. I did a small set zoomed in to 2500m and moving away from the equator. Those numbers ended up pretty close to each other.

Log info
50000m zoom
[SINGLE TOUCH TO THE MAP]
MapClickedListener: On Touch: LatLonPoint[lat=34.69682246526478,lon=-86.56669172935936]
MapClickedListener: On Touch x,y: Point(624, 287)
PickNavigateController: ACTION_UP evt NOT dragging. Picks 0.
MapClickedListener: ClickType: CLICKED
MapClickedListener: on Event Single Press: LatLonPoint[lat=34.69638638712407,lon=-86.56609375423172]
[LONG PRESS TO THE MAP]
MapClickedListener: On Touch: LatLonPoint[lat=34.69682246526478,lon=-86.56669172935936]
MapClickedListener: On Touch x,y: Point(624, 287)
PickNavigateController: Long Press 0
MapClickedListener: ClickType: LONG_PRESS
MapClickedListener: on Event Long Press: LatLonPoint[lat=34.69638638712407,lon=-86.56609375423172]
MapClickedListener: Distance between touch and long press: 73.07587954789241
MapClickedListener: On Long Press x,y: Point(624, 287)

10m zoom
[SINGLE TOUCH TO THE MAP]
MapClickedListener: On Touch: LatLonPoint[lat=34.68413190998026,lon=-86.6487055783966]
MapClickedListener: On Touch x,y: Point(554, 350)
PickNavigateController: ACTION_UP evt NOT dragging. Picks 0.
MapClickedListener: ClickType: CLICKED
MapClickedListener: on Event Single Press: LatLonPoint[lat=34.684131887719715,lon=-86.6487055025367]

[LONG PRESS TO THE MAP]
MapClickedListener: On Touch: LatLonPoint[lat=34.68413190998026,lon=-86.6487055783966]
MapClickedListener: On Touch x,y: Point(554, 350)
PickNavigateController: Long Press 0
MapClickedListener: ClickType: LONG_PRESS
MapClickedListener: on Event Long Press: LatLonPoint[lat=34.684131887719715,lon=-86.6487055025367]
MapClickedListener: Distance between touch and long press: 0.0073648950868234085
MapClickedListener: On Long Press x,y: Point(554, 350)
System.out: Got a long press at latitude: 34.684131887719715 Longitude: -86.6487055025367

1000m zoom
[SINGLE TOUCH TO THE MAP]
MapClickedListener: On Touch: LatLonPoint[lat=34.765178249375595,lon=-86.41371591023108]
MapClickedListener: On Touch x,y: Point(815, 189)
PickNavigateController: ACTION_UP evt NOT dragging. Picks 0.
MapClickedListener: ClickType: CLICKED
MapClickedListener: on Event Single Press: LatLonPoint[lat=34.76517061862333,lon=-86.41370651566413]

[LONG PRESS TO THE MAP]
MapClickedListener: On Touch: LatLonPoint[lat=34.765178249375595,lon=-86.41371591023108]
MapClickedListener: On Touch x,y: Point(815, 189)
PickNavigateController: Long Press 0
MapClickedListener: ClickType: LONG_PRESS
MapClickedListener: on Event Long Press: LatLonPoint[lat=34.76517061862333,lon=-86.41370651566413]
MapClickedListener: Distance between touch and long press: 1.2068360080193425
MapClickedListener: On Long Press x,y: Point(815, 189)
System.out: Got a long press at latitude: 34.76517061862333 Longitude: -86.41370651566413

[JACochran]

Calling containerToGeo in the OnTouch method converts the touch location to a GeoPosition on the map. If you notice that containerToGeo takes in int values, so the pixel location that was originally a double value is truncated. This causes the discrepancy to the values you see with MapUserInteractionEvent. With MapUserInteractionEvent we calculate the GeoPosition using the double value, which is much more precise. We also pass back the pixel coordinates as int values versus their original double type due to android.graphics.Point only accepts int values. Therefore, if you reverse calculate the GeoPosition, precision will be lost. The GeoPosition being returned in the MapUserIneteractionEvent is recommended over reverse calculating the GeoPosition using containerToGeo.

[JACochran]

12-20 10:04:54.389 3727-3727/mil.emp3.dev_test_sdk D/MainActivity: Map User Interactive Event: CLICKED X/Y: 302 / 806 Lat: 39.9395810699428 Lon: -105.20784608281856
12-20 10:04:54.390 3727-3727/mil.emp3.dev_test_sdk D/MainActivity: Map User container to geo: Lat/Lon: 39.93990399775787 / -105.20801032091879
12-20 10:04:54.390 3727-3727/mil.emp3.dev_test_sdk D/MainActivity: Map User container to geo Float: Lat/Lon: 39.9395810699428 / -105.20784608281856

The first print statement is the location that we calculate ourselves,
the next print statement is using the old method containerToGeo with integer pixel coordinates,
the next print statement is using the new method containerToGeo with float pixel coordinates.

Now the reverse calculation can be calculated accurately using the pixel float coordinate values.