Excel Query

[EHM-0654 Murray]

I'm trying to build myself a spreadsheet to assist me with my VFR flight planning, but I've hit a snag that I cannot readily get my head around...

I need to calculate theta, the angular difference between the true course and the wind direction. For us humans, that's pretty easy as we can get our heads around the 001-360-001 thing (so, for a TC of 092 and a wind bearing of 320, theta is 132...) but I'm having trouble expressing it in an Excel formula that gets the right figure 100% of the time.

Anyone feel like jumping in and assisting me?

[EHM-1703 Philip]

Murray,

All sounds way too complicated to me...... BUT! I am a bit of an excel freak and I am sure there is a Theta calculation called "imargument". Don't ask me how it works and it may only be an Engineering function in Excel 2003, but try searching for it in Office Help or MS online help, it could do what you need as it returns a value in Radians.

Sorry I can't be of more help, but it may help you on your way.

Cheers

[EHM-1703 Philip]

Ooo! I have just had a look myself on the MSDN website and you may have to install the Analisys toolpack to use it. It is available in Excel 97 onwards. (Dig out those Instalation Disks)

[EHM-0654 Murray]

Cheers Phil, knew someone out there would be an Excel-head...

Where did I put that Office 2003 CD?

[EHM-1328 Willem]

You mean something like this???





Willem,  EHM1328

[EHM-0654 Murray]

Hmm... yes Willem, that kind of a thing...

I'm going to post a thread somewhere about this, as I find it really useful in all the VFR flying I'm doing currently, but I found a web page that explains mental calculations suitable for VFR flight planning. At the moment, I'm using a combination of a spreadsheet and the procedures outlined on said webpage to calculate wind-adjusted headings and ETEs, and it's been good enough for the VFR WT so far (I'm landing pretty much on the nose as far as FSP is concerned!)