Changes between Version 5 and Version 6 of ZoomLevels

Timestamp:

Jul 27, 2018 9:05:24 PM (7 years ago)

Author:

Uriel

Comment:

--

ZoomLevels

@@ -36 +36 @@
 
 4. And so on, starting the each 7 degree window at the rounded-down (westward, really) coordinate of the previously generated tile. 
+
+This math should work just as well for any higher zoom level, but in order to go ''lower'', you'll need more than 7 tiles. Probably twice as many, which really means 4 times as many since each slice is a square and not a line. A 7x7 tile window, at full resolution, requires 141.3 MB of the SRTM3 data, which is very reasonable. It would require 1.27 GB of the SRTM1 data, which is tight but certainly doable on a machine with 16 GB of RAM!
+
+Instead, to do lower zoom levels, calculate the correct amount of SRTM tiles and then load them in using sampling rates other than 1. Remember, a sampling rate of 2 reduces the memory requirement of each tile by 4; a rate of 3 reduces it by 9. This adds up to a lot of memory savings. And at lower zoom levels you really don't need the full resolution, the maps will look just as good.