why is there no spherical solution to the direct geodesy problem? There is!

[StephenG1CMZ]

Yes Sliderule, that has tickled my interest. Thank you all for your helpful replies.
I would love to read those references to help understand and visualise the transformations, rather than just follow them - but my local library rarely has any books.

I also asked the question on Yahoo Answers and Morningfox pointed me to a solution on Movable- types website that I had missed:
https://uk.answers.yahoo.com/question/in...438AAMKcRG

I had delayed replying for a few days hoping to have incorporated the routine into my Geodesy API on the HP Prime - but I seem to have messed up my implementation and my Direct routines aren't yet right.
http://www.hpmuseum.org/forum/thread-7062.html