PIC32mx340f128h nrel code conversion

I am looking for formula to calculate sun elevation angle from below data .I have download into excel sheet by providing required latitude and longitude.

Question are:

How to calculate Elevation Angle from zenith and azimuth angle.
what is refer Top. azimuth angle (westward from S) & Top. azimuth angle (eastward from N) from image
What is converted elevation formula to determine elevation angle from east to west
i tried below code on above ic i.e chipkit uno32 with MPIDE IDE. with integer value is working fine it give almost equal value when code run on visual studio, but when self incremented timer function attached zenith and azimuth almost remain same but date and time are getting accumulated properly.