I am working on creating a spreadsheet that is going to calculate the most ideal position someone should be laying in for the maximum sun exposure based on time, day of the year, time zone and GPS/LAT/LON.

I am working on building a program that ingests these items, and references the Solar Azmuth Angle (which direction the sun is) along with the Solar Zenith Angle (how high the sun is), and spit out a direction (180 through -180), we could show that graphically on a simple 360 dial interface.

Maybe most of the work is done here already, but I am not sure how to incorporate it into a program/Excel document: http://www.nrel.gov/midc/solpos/spa.html.

Below is the basic breakdown I have in a spread sheet. I am using the LAT/LONG of my house @ 12pm today. Just need to figure out what calculations to plug in to figure out where the arrow would be pointing to tell people where to lay their feet. I am thinking along the lines of the time on a clock (e.g 3pm). Not super worried about the adding the elevation part into the equation right now. It would just be a "wish list" item.

Input
LAT 40.8062861
LONG -77.9249305
Time 12:00
Time Zone EST
Elevation ???

Output
Feet
Head

Let me know if you anyone has any thoughts on this.