The Pocket PolyLine for GroundOverlays is based upon this Google API Maps Tutorial Example.
Below is a 'screenshot' of the red-bordered image-area indicator seen on the Google API map, when you first logged onto the 'It’s the Pocket PolyLine for GroundOverlays!' web page:
Let’s change the 'Image Width-to-Height Ratio' of the red-bordered image-area indicator to reflect the dimensions of a '260-pixels' (height) by '425-pixels' (width) GroundOverlay image, by typing '260' and '425' into the 'Image Height (in pixels)' and 'Image Width (in pixels)' text-boxes, respectively:
[Below is a '260-pixels' by '425-pixels' GroundOverlay image, showing the skyline of the city of Lakeland, Florida, in the early 1920s, that will be used for this example:]
[The image above is from this Wikipedia article. You can 'save' the 'pubic domain' image above to your computer, or 'download' the image directly from Wikipedia.]
Now, let’s move the 'Blue Plane' (destination) icon to the west of the 'Green House' (center) icon until the 'Blue Plane' icon is just to the east of Crystal Lake, and the connecting red indicator line is in the direction of the city of Lakeland, Florida:
The yellow-colored rectangle super-imposed on the 'screenshot' below demonstrates how the GroundOverlay image will be rotated to reflect the approximate minus 79-degree 'heading' of the connecting red indicator line. The top of the rotated GroundOverlay image will sit just south of Crystal Lake, and the bottom of the GroundOverlay image will sit north of the city of Winter Haven, Florida, once the 'KML code' (that is generated in the 'GroundOverlay Polypocket') is 'copied-and-pasted' into this kml test-file, and the file then opened in your Google Earth 3D Viewer. You will have to 'save' the kml test-file to the same folder on your computer that you will 'save' the Lakeland skyline image further up the page, for the kml test-file to display properly in your Google Earth 3D Viewer.
[You may also 'copy-and-paste' this text-version of the 'groundOverlay_test_file.kml' test-file into your text editor, and 'save' it as ('groundOverlay_test_file.kml').]
Once the pre-formatted 'KML code' for your GroundOverlay’s 'LatLonBox' element, and for your KML 'LookAt' or 'Camera' element’s 'longitude,' 'latitude,' and 'heading' elements, are 'copied' from the 'GroundOverlays PolyPocket' and then 'pasted' into the 'groundOverlay_test_file.kml' test-file—replacing the current HTML-code elements with those same names—and the 'groundOverlay_test_file.kml' test-file is then opened in your Google Earth 3D Viewer (and the 'Google Tour' started)—you will see the results of the Green House icon and Blue Plane icon re-positioning:
Note-1: The HTML-code for the It’s the Pocket PolyLine for GroundOverlays! file can be found here:
Pocket PolyLine for GroundOverlays HTML-code.
Have fun creating 'KML' GroundOverlay code with the aid of the Pocket PolyLine for GroundOverlays!