figured out columns, I think.
>>> s=get_column(read(get_hgt_file('36', '-115')[0]), 0); print repr(s[:16])
'\x03\x1f\x03!\x03"\x03"\x03"\x03!\x03!\x03!'
>>> t=get_column(read(get_hgt_file('36', '-116')[0]), 1200); print repr(t[:16])
'\x03\x1f\x03!\x03"\x03"\x03"\x03!\x03!\x03!'
>>> s[:16]==t[:16]
True
>>> s==t
False
so the last two bytes of each 2402-byte line of the westerly quadrant matches (more or less closely) the first two bytes of the same line of the easterly quadrant. so sample order is west to east. and latitude-wise, north to south. which makes the first two bytes of the final 2402-byte line of a NW sector file the eponymous sample. and I suppose, which makes the filename misleading, as N36W116.hgt actually contains samples from the N36W115 quadrant, except for the overlap column in the first two bytes of each line.
so, when dealing with the NW sector, joining a number of hgt files together to plot an area, one should discard the first 2402 bytes of each file, and the first two bytes of each line. or better yet, average those values with the matching lines in the surrounding files, as my friend Dan Lyke indicated to me the other day.
why am I going through all this head-hurt? for a paying job, perhaps? nope. I have another friend who is so paranoid of government that he has latched on to "flat earth" theory, what I've been calling "Dark City" theory by its similarity to the movie's premise. I want to write a program that can possibly prove to him that this is a lie, intended to divert our attention from the equally sinister but less complicated mess we're really in.
last updated 2016-03-23 00:43:02. served from tektonic.jcomeau.com