Sunrise time

[akinvic]

Hi Steve,

I'm sure you hear it all the time that Cumulus is truly a great product and the work you've put into it is nothing short of outstanding. I've only been using it a couple of weeks, but I definitely agree!

This might be a stupid question. One thing I can't quite figure out is Cumulus' sunrise times are a few minutes off (earlier) than that of what my other software reports (Weatherlink, for instance). I'm using the same exact lat/long coordinates, time zones, etc. A quick check at http://www.hia-iha.nrc-cnrc.gc.ca/sunrise_adv_e.html (good for only Canadian locations) confirms this. Is this because of elevation (mine is 65m/213ft)?

BTW, my lat/long: 48,29,8 - 123,19,14 (degrees)
What Weatherlink reports is http://www.vicweather.net/AKWeather.htm, Cumulus http://www.vicweather.net/cumulus/index.htm

Cheers,
Andreas

[steve]

Just using a slightly different algorithm, I guess. I have no idea what algorithm is used by the routines which Cumulus uses. It's possible I'm introducing an error somewhere in my position calculations or timezone conversions. Have a look in cumulus.ini, where you'll see your co-ordinates in decimal, see if they are what you expect.

Have you tried the moon times yet? Do they have a similar discrepancy?

Steve

[akinvic]

Sorry Steve I was editing my original post and you had already replied

Only the sunrise is different, perhaps three minutes or so, and it's always earlier. Not sure if it's the elevation or something. Is anyone else noticing this?

And, no I haven't tried moon times (it's less important to me so I don't really care anyway )

[TNETWeather]

I update to see the new moon values and they are off a bit from say WD for example same as the sun settings...

Personally, anything in the general area is good enough for me. I doubt many places have a direct line of sight of the horizons to "see" a difference.

I had in the past used moon rise/set charts to get the values as I was unable to find a decent calculation (actually one that I could then code)... and that worked well, but is is messy to setup.

[steve]

I seem to be calculating latitude and longitude in decimal correctly from deg/min/sec, and I have similar discrepancies here, so it's not a timezone thing.

I've found out the algorithm that's used, it's from:

Astronomical Algorithms, Jean Meeus, Willmann-Bell, 1991.

Steve

[akinvic]

Steve,

I checked the cumulus.ini file and it seems to be reporting correctly as well.

A good website for doing the degree/decimal conversion is this: http://www.fcc.gov/mb/audio/bickel/DDDMMSS-decimal.html

In any case, whatever is causing it is not a big concern to me but just something I noticed. It certainly doesn't make me enjoy the software any less

Cheers,
Andreas

[steve]

It's interesting, all the same

I happen to have another library routine to hand, so I plugged it in, and it seems to come up with better results than the other one, so I think I'll use that instead.

Steve

[akinvic]

Hi Steve

Looks like the algorithm you are using in the new beta (build 574) is working as it should. Great stuff!

Cheers,
Andreas