Celestial navigation. Fix by two circles of position: vector solution. With a sextant take two altitudes, correct them and obtain the observed altitudes: Ho. Take the Nautical Almanac and find the coordinates of the celestial bodies: GHA, declination. Use this app to calculate the two solutions, and to plot the circles of position, or circumferences of equal altitude on Google maps. Running fix: - The app moves the first sight to the time of the second, taking into account the motion of the observer. Method explained in the papers: - Vector Solution for the intersection of two Circles of Equal Altitude. (Andrés Ruiz González. Journal of Navigation 2008, 61:355-365. The Royal Institute of Navigation). - Use of rotation matrices to plot a circle of equal altitude. (Andrés Ruiz. JOURNAL OF MARITIME RESEARCH, Vol 8, Nº3, 2011) Available on the author's website. - Output is copied to clipboard User interface: - Zoom buttons +/- - Map types: normal and satellite - GPS location. ("Location" App permission must be allowed. Switch on you GPS, and then automatic location detection is possible)