<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta content="text/html;charset=UTF-8" http-equiv="Content-Type"></head><body ><div style="font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 10pt;"><div>Hello,<br></div><div><br></div><div>I think I may have found a small error in the above mentioned projection (file ocea.cpp). The error can be directly traced to Snyder and the numerical example he gives for the spherical form of this projection.<br></div><div><br></div><div>In his numerical example (page 279, formula for x) Synder has the following derivations:<br></div><div>0.98X arctan [-0.6223338/(-0.9720102)l<br></div><div>= 0.98X(0.5694937 + rr), adding .rr since denominator is negative.<br></div><div><br></div><div>In ocea.cpp (line 29) this translates into the following code:<br></div><div>if (t < 0.)<br></div><div> xy.x += M_PI;<br></div><div><br></div><div>I believe that Synder should have subtracted M_PI as the numerator of the atan fraction is negative (see Snyder page ix discussion about ATAN2 function) and consequently ocea projection should also use atan2.<br></div><div><br></div><div>I have to admit I'm writing this with a certain trepidation as reporting an error in Snyder is almost like finding faults in the Bible, but I'd like to have this clarified.<br></div><div><br></div><div>The error is probably insignificant and I ran into it only because I'm working on an online version of the Snyder book. You can check it at <a target="_blank" href="https://neacsu.net/docs/geodesy/snyder/">https://neacsu.net/docs/geodesy/snyder/</a> Currently I'm transcribing the numerical examples to JS and MathJax and that's how I ran into this issue.<br></div><div><br></div><div>Thank you for looking into it.<br></div><div class="zmail_signature_below"><div id="" data-zbluepencil-ignore="true" data-sigid="5934168000004827002"><div>-- <br></div><div><br></div><div>Mircea Neacsu <br></div></div></div><div><br></div></div><br></body></html>