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| mission:tech:odyssey:sku:position-to-timezone [2012/03/04 00:16] – [Position to Timezone Tracking] chrono | mission:tech:odyssey:sku:position-to-timezone [2016/03/24 22:30] (current) – [Moving to python] chrono | ||
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| + | ====== Position to Timezone Tracking ====== | ||
| + | The task seems trivial at first glance: Develop a system that automagically identifies the timezone of [[mission: | ||
| + | |||
| + | It proved to be a bit more difficult, since time borders are not systematic, but chaotic, following political (national) borders, making a simple mapping almost impossible or at least very costly in terms of performance and maintenance (time borders and DST usage change often). | ||
| + | |||
| + | Apollo-NG Time is always GPS disciplined UTC, local time is adjusted by referencing UTC as default system time and applying the correct timezone with accurate DST adjustments to the system. This way, even international-date-border crossings in either direction won't affect the system. | ||
| + | |||
| + | {{: | ||
| + | |||
| + | ===== Solution in C w/ ImageMagick ===== | ||
| + | |||
| + | The simplest method found, was introduced by anselm@hook.org: | ||
| + | |||
| + | <sxh c; collapse: true; toolbar: true> | ||
| + | // A utility to take a longitude latitude and return a time zone in olson posix string format | ||
| + | // by anselm@hook.org | ||
| + | // this was based on data from | ||
| + | // http:// | ||
| + | // which was loaded into mapserver and each layer rendered as a unique color to a large image | ||
| + | // this code looks up that color on the map and then returns the appropriate indexed string | ||
| + | // see also | ||
| + | // http:// | ||
| + | i=iN8SSo-pO5iG8gT9qsCBBA& | ||
| + | |||
| + | #include < | ||
| + | #include < | ||
| + | #include < | ||
| + | #include < | ||
| + | #include " | ||
| + | |||
| + | #define CONVERTNAME " | ||
| + | #define CONVERTPATH "/ | ||
| + | #define INCANTATION_BUFFER_SIZE 999 | ||
| + | |||
| + | int main(int argc,char **argv) { | ||
| + | if(argc <3 ) { | ||
| + | | ||
| + | | ||
| + | } | ||
| + | char incantation[INCANTATION_BUFFER_SIZE]; | ||
| + | int timezones_length = sizeof(timezones)/ | ||
| + | int zonecode = 0; | ||
| + | // get user supplied location | ||
| + | double lon = atof(argv[1]); | ||
| + | double lat = atof(argv[2]); | ||
| + | // convert to equidistant projection | ||
| + | int x = 2048.0f/ | ||
| + | int y = 1024.0f/ | ||
| + | int r,g,b; | ||
| + | printf(" | ||
| + | printf(" | ||
| + | snprintf(incantation, | ||
| + | | ||
| + | "/ | ||
| + | printf(" | ||
| + | FILE* f = popen(incantation," | ||
| + | while( fgets(incantation, | ||
| + | printf(" | ||
| + | fclose(f); | ||
| + | sscanf(incantation," | ||
| + | printf(" | ||
| + | zonecode = ((r& | ||
| + | if(zonecode > timezones_length) { | ||
| + | printf(" | ||
| + | } else { | ||
| + | printf(" | ||
| + | } | ||
| + | } | ||
| + | |||
| + | ################################################################### | ||
| + | |||
| + | timezones.h | ||
| + | |||
| + | char* timezones[] = { | ||
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| + | "" | ||
| + | }; | ||
| + | </ | ||
| + | |||
| + | Execution time: 0m3.846s | ||
| + | ===== Moving to python ===== | ||
| + | |||
| + | Having to have to maintain a binary for embedded systems seemed cumbersome and imagemagick is - although glorious - not really something for embedded systems. Python however is the default script language on all gentoo systems and therefore automatically available on all hosts. | ||
| + | |||
| + | The following python script only needs PIL (Python Imaging Library) which is much leaner and returns results faster with less system impact. The 6Mb TIFF File was converted to a PNG (see/ | ||
| + | |||
| + | <sxh python; toolbar: false> | ||
| + | # | ||
| + | # -*- coding: utf-8 -*- | ||
| + | |||
| + | # Deps: PIL (Python Image Library) | ||
| + | |||
| + | import os, sys | ||
| + | import Image | ||
| + | |||
| + | timezones = [ | ||
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| + | "" | ||
| + | |||
| + | lat = float (sys.argv[1]) | ||
| + | lon = float (sys.argv[2]) | ||
| + | |||
| + | # convert to equidistant pixel projection ################ | ||
| + | |||
| + | x | ||
| + | y | ||
| + | |||
| + | tz_map | ||
| + | tz_pix | ||
| + | |||
| + | r,g,b | ||
| + | tz_code | ||
| + | |||
| + | if | ||
| + | print " | ||
| + | else: | ||
| + | print " | ||
| + | |||
| + | </ | ||
| + | |||
| + | Execution time: 0m1.824s | ||
| + | |||
| + | If you can find an easier and reliable way with even less impact, don't hesitate to submit your solution to be published here as well. | ||
| + | |||
| + | {{tag> | ||
| + | |||
| + | {{keywords> | ||
| + | |||
| + | |||
| + | ~~DISCUSSION~~ | ||