For verifying the corridor arrangement, draw labels on every
loaded tile (per drawTileAt):
- 'N' at the canvas top edge of the tile (= image north after UNPACK_FLIP_Y_WEBGL)
- 'S' at the canvas bottom edge (= image south)
- 'x=NNN y=NNN' at the centre with the actual ESRI tile coords
This lets you see at a glance which canvas direction maps to which
world direction. Combined with #flight=N|... and #fetch=N|... you
can describe exactly what is wrong (e.g. N pointing in screen-up
direction when it should point at the corridor front).
Richard Zink
6e96c5ffad