Too much memory to store every associated point for every tile. I am pretty sure javascript does not duplicate the objects but stores references. Still, at 1000, the performance is pretty slow. At 100 it is good, 10-30 milliseconds to build each tile URL.

The URLs are too long. I think IE has a 2000 char limit. Can’t do post, because the Google tile overlay works with GET to get each tile URL. Could split it into two, one post and one get with a token, but that would require a sessionful service, which I am trying to avoid. Thought about using Google extended encoding as explained n their chart api page. If I am willing to go from 256 columns to 64 columns and 256 rows to 64 rows, that would work (64 * 64 is 4096, which is how many values the 2-digit encoding gives you). Still doing the math to see if it would work by doing 128 × 128. That would make things only 1 pixel off 64 could make things 2-3 pixels off

x 0 0 0 × 0 0 0 0 × 0 0 0 × 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
x 0 0 0 × 0 0 0 0 × 0 0 0 × 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
x 0 0 0 × 0 0 0 0 × 0 0 0 × 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
x 0 0 0 × 0 0 0 0 × 0 0 0 × 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Averaging ~50 milliseconds for 10 points
~ 800 milliseconds for 100 points
~ 10,000 milliseconds for 1,000 points
10,000 points just drags on and on