Hello,
I have been using the geod command in the proj package to perform
geodetic forward calculations. My testing has produced some rather
unusual output, captured here:
Script started on Wed Jul 14 15:08:01 2021
geography.657$ uname -a
OpenBSD ip72.ok.cox.com 6.9 GENERIC.MP#3 amd64
geography.658$ geod +ellps=sphere +units=km << END
> 0N 0E 269d58' 100.0
> 0N 0E 269d59' 100.0
> 0N 0E 270d 100.0
> 0N 0E 270d1' 100.0
> 0N 0E 270d2' 100.0
> END
0d0'1.883"S 0d53'57.559"W 89d58'0.015"
0d0'0.942"S 0d53'57.559"W 89d59'0.007"
0dN 0d53'57.559"E -90d
0d0'0.942"N 0d53'57.559"W 90d0'59.993"
0d0'1.883"N 0d53'57.559"W 90d1'59.985"
geography.665$ ^D
Script done on Wed Jul 14 15:08:18 2021
I intended to make five steps of 100 km west from the geographic origin.
It appears that steps approximately west go into the western
hemisphere, as expected. In the third calculation, stepping exactly
west, 270 degrees, obtains a terminus to the east.
This only occurs on my two OpenBSD machines. Other platforms produce
output like:
Script started on 2021-07-14 15:05:18-05:00 \
[TERM="screen" TTY="/dev/pts/3" COLUMNS="108" LINES="53"]
gcarrie@aht.1$ uname -a
Linux aht 5.11.0-7614-generic #15~1622578982~20.04~383c0a9-Ubuntu SMP \
Wed Jun 2 00:57:14 UTC 2 x86_64 x86_64 x86_64 GNU/Linux
gcarrie@aht.2$
gcarrie@aht.2$ geod +ellps=sphere +units=km << END
> 0N 0E 269d58' 100.0
> 0N 0E 269d59' 100.0
> 0N 0E 270d 100.0
> 0N 0E 270d1' 100.0
> 0N 0E 270d2' 100.0
> END
0d0'1.883"S 0d53'57.559"W 89d58'0.015"
0d0'0.942"S 0d53'57.559"W 89d59'0.007"
0dN 0d53'57.559"W 90d
0d0'0.942"N 0d53'57.559"W 90d0'59.993"
0d0'1.883"N 0d53'57.559"W 90d1'59.985"
gcarrie@aht.3$
gcarrie@aht.3$ exit
Script done on 2021-07-14 15:05:39-05:00 [COMMAND_EXIT_CODE="0"]
Here the outputs match, except for the 270 degree step, which ends up
east instead of west, which is more what I expected.
Please advise if I am misunderstanding the command, or options, or
program.
Thanks,
Gordon Carrie
