Solar Polar Compass uses the suns position in the sky to calculate where north is. By aligning the lines on screen with the shadow of a vertical object, your phone and screen guidelines will be exactly aligned north-south. Ideal for astrophotographers who want to set up in the daytime, and useful for anyone who needs to know where true north is to a high degree of accuracy. Solar Polar Compass is much more accurate than a magnetic compass, which does not align with true north, and on a phone may need calibration or oscillate around magnetic north.To use, wait for your GPS coordinates to load, or type them manually. The app will use your phones time and timezone to calculate solar azimuth using the NOAA formulas. On screen, angled lines will appear. Line these up with a shadow (multiple lines are provided for optimal phone positioning). The rounded end of the central line should be towards the sun. The top of your phone is pointing north in the northern hemisphere, south in the southern hemisphere. The sides of the phone and guidelines on screen are aligned precisely north-south. The display updates continuously.