# use of cart2sph not in line with manual

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## use of cart2sph not in line with manual

 Dear madam/sir, I have been struggling with the function (theta,phi,R) = cart2sph(x,y,z) for some time and found out that the description in the octave manual is not exactly in line with its behaviour. But I found out that: In the manual it is told that: 'theta represents the angle relative to the positive x-axis' The angle relative to the positive x-axis is mathematically defined as the dotproduct of a position vector r with the unitvector in the x-direction. This is in line with default mathematical representation of spherical polar coordinates where theta represents the angle between position vector and unitvector z axis. I assumed from the description in the manual that in Octave unit x took over the role of unit z, which apparently isn't. Moreover, the angle phi is the elevation angle above the x-y-plane. However, I found out that the angle theta using cart2sph is defined as the angle of the orthogonal projection of position vector r onto the xy plane with the unitvector x. This is in line with the definition of cart2sph in MatLab, where it is explicitly said that theta represents the azimuth angle and phi the elevation angle. This is in line with the description in the Octave manual. It would be nice and less confusing if the words azimuth and elevation were used in this context, if possible with a small graph. Sincerely yours, Dr. J.A. Piest Nijmegen The Netherlands HOWEVER: ------------------------------------------------------------------------------------ example publication: CRDS of thin layers : www.darklands-sewer-system.eu/outlet/FTP/CavityRingdownPaper.pdf sailing: SV Morgenster bottom-up : www.darklands-sewer-system.eu/outlet/FTP/bottom-up-small.mov SV Morgenster top-down  : www.darklands-sewer-system.eu/outlet/FTP/top-down-small.mov rowing: 8+ : www.darklands-sewer-system.eu/outlet/FTP/RowingTheClubAcht-28February2015-small.mp4