I am Xojo developer, working on navigation software application.
my application concern geodetic science, on oblate and spherical earth.
my question is really very small detail about great circle tracks.
Everything is working properly, i am trying to resolve the problem of longitudes Way points.
So, when for e g, longitude of departure is 013°25' W and arrival is 075°W, west bounding , with longitude difference between Way points "DLo", is 5°.
My program compute legs from 013° 25'W each 5°, it means that the next wp longitude will be 018°25'W, etc ...
I am looking for solution to convert the first wp to integer value multiple of "Dlo"=5°, thus next must be 015 00W , 020 00W , 025 00W, etc.
Whit this way, its more easy for the user to plot the way points and the path on a plotting sheet with integer values of longitude.
This image is the longitudes wp output that i want to do: