This repository contains four implementations of sunrise calculations.
cpp/redshift_solar.c: copied from the redshift project for reference. It actually contained a bug, though. This file also is the reason why the test code is GPL licensed. My implementations of the calculation are MIT licensed though.cpp/wiki_sun.cpp: is the algorithm described on Wikipedia. It appears to be an approximation. It's results are slightly off in moderate latitudes and unusable in polar latitudes (the sun sets for a polar day). It's faster though, but the other calculations aren't "slow" in practice, either.cpp/noaa_sun.cpp: the result of the situation rendered by the above. I downloaded the NOAA spreadsheets, was able to comprehend the two-pass calculation done by existing implementations and could even match it with the output of timeanddate.com. So, this apparently is what everybody does and I reimplemented the spreadsheet cell by cell and now have my own MIT-licensed code. :)rust/src/lib.rs: this is my implementation, but ported to Rust. Just to compare it to C++ and do some FFI hacking.
See the cpp/sun.h header for available public functions. The CMake project currently is dumb, so the
easiest way to use this in a project is to copy the required files (angle.h, julian_date.h, sun.h
and whatever implementation you choose) and integrate them with your build system.
You need date for the library until we have C++20 chrono.
For the benchmark and test code, you'll also need fmt and
benchmark installed on your system, as well as Rust.
I wrote these implementations for the fun of doing it. And maybe for the fun of building products with stupidly precise astronomic calculations. I know we'll probably never sell to the Arctic, but if we do, at least my sunrise calculation is correct! Therefore, personal code.
Feel absolutely free to use this for your projects. And please let me know if this makes it into some actual POS product. ;)