User feedback: x decreasing left-to-right (matches NO swap), y
increasing in flight direction (matches swap). So the swap on
canvasY is right but the swap on canvasX was wrong direction.
With the no-swap canvasX formula:
- perp = -2 (east, dx=+2) at canvasX = 128 (left)
- perp = +2 (west, dx=-2) at canvasX = 1152 (right)
After UNPACK flip: canvasX stays as-is. User at canvas right sees
west (low x). User at canvas left sees east (high x). x decreases
left-to-right in the label content, matching what the user sees
in the satellite imagery too.
(The Y swap remains so lng=+12 -> canvasY=128 -> screen top, so
north tiles still appear at the top of the screen.)
Richard Zink
d063e5e864