language agnostic - Computing Earth orbit position and rotations -


i want compute earth position (relative sun) , axis rotations given date , time. it's ok assume sun stationary @ 0,0,0 coordinate. minor deflections, due moons gravitational pull example, can ignored. accurate within degree or enough.

are there libraries/source/data out there me accomplish this?

the aa-56 code, which can downloaded here, includes solar ephemeris meet needs. high-precision work you'd want more accurate jpl's de421, there inconveniently large tables of coefficients involved, , it's extreme overkill if you're happy 1 degree accuracy.

the earth's rotation @ given time given greenwich sidereal time.
jean meeus' "astronomical algorithms" (a reference have these sorts of calculations!) gives formula theta0 (cumulative rotation angle in degrees) in terms of julian date jd:

t = (jd - 2451545.0 ) / 36525  theta0 = 280.46061837 + 360.98564736629*(jd-2451545.0) +             0.000387933*t*t - t*t*t/38710000.0

theta0 = 0 degrees mod 360 represents instant when greenwich meridian aligned right ascension 0:00 in celestial coordinates.


Comments

Post a Comment

Popular posts from this blog

asp.net - repeatedly call AddImageUrl(url) to assemble pdf document -

i'm using abcpdf , i'm curious if can recursively call addimageurl() function assemble pdf document compile multiple urls? something like: int pagecount = 0; int theid = thedoc.addimageurl("http://stackoverflow.com/search?q=abcpdf+footer+page+x+out+of+", true, 0, true); //assemble document while (thedoc.chainable(theid)) { thedoc.page = thedoc.addpage(); theid = thedoc.addimagetochain(theid); } pagecount = thedoc.pagecount; console.writeline("1 document page count:" + pagecount); //flatten document (int = 1; <= pagecount; i++) { thedoc.pagenumber = i; thedoc.flatten(); } //now try again theid = thedoc.addimageurl("http://stackoverflow.com/questions/1980890/pdf-report-generation", true, 0, true); //assemble document while (thedoc.chainable(theid)) { thedoc.page = thedoc.addpage(); theid = thedoc.addimagetoc
Read more

java - Android recognize cell phone with keyboard or not? -

in android app, want detect user's device if device has keyboard(like motorola milestone) , show corresponding user interface. guys know how that? ! regards justicepenny http://developer.android.com/reference/android/content/res/configuration.html public int keyboard the kind of keyboard attached device. 1 of: keyboard_nokeys, keyboard_qwerty, keyboard_12key. that's it!
Read more

iphone - How would you achieve a LED Scrolling effect? -

how achieve led scrolling effect example below? led sign - led ticker emulator iphone , ipad http://img.skitch.com/20101201-rsfh4p1bajb1wp94k466pdpiuj.preview.jpg sometimes remunerates comment in other posts :) have put code you, should implement font '8pin matrix' realistic feeling. uilabel *label; - (void)viewdidload { [super viewdidload]; label = [[uilabel alloc]initwithframe:cgrectmake(10, 50, 300, 20)]; label.font = [uifont fontwithname:@"courier-bold" size:16.0]; label.backgroundcolor = [uicolor blackcolor]; label.textcolor = [uicolor greencolor]; label.linebreakmode = uilinebreakmodecharacterwrap; // otherwise "…" label.text = @"this led text scrolled "; // blanks space between [self.view addsubview:label]; [nstimer scheduledtimerwithtimeinterval:0.12f target:self selector:@selector(scrolllabel) use
Read more