Diving data loop closures altering depths

[Footleg]

A simple example data file follows. Two lengths of diving data forming two
sides of a loop. Both end at the same depth. Joining the ends to close the
loop causes the depth of the stations 4 and 'd' to change from -5.8m to
-5.95m. Creating the same series of legs in normal tape,compass,clino
format and closing the loop causes the depth of the stations 4 and 'd' to
change from -5.8m to -5.78m. Clearly something different (and undesirable)
appears to be happening in loop closures on diving data.

-----------------------------------------

*begin divingtest

*fix Ent 0 0 0
*entrance Ent

*equate Ent dive_open.0
*equate Ent dive_closed.0
*equate Ent normal_open.0
*equate Ent normal_closed.0

*begin dive_open

*data diving from to bearing length fromdepth todepth

0 1 330 17.40 0 -02.00
1 2 350 03.20 -02.00 -03.30
2 3 020 10.70 -03.30 -05.90
3 4 070 12.90 -05.90 -05.80

0 a 045 13.80 0 -02.90
a b 021 07.80 -02.90 -03.90
b c 340 15.00 -03.90 -04.20
c d 350 04.35 -04.20 -05.80

*end dive_open

*begin dive_closed

*equate 4 d

*data diving from to bearing length fromdepth todepth

0 1 330 17.40 0 -02.00
1 2 350 03.20 -02.00 -03.30
2 3 020 10.70 -03.30 -05.90
3 4 070 12.90 -05.90 -05.80

0 a 045 13.80 0 -02.90
a b 021 07.80 -02.90 -03.90
b c 340 15.00 -03.90 -04.20
c d 350 04.35 -04.20 -05.80

*end dive_closed

*BEGIN normal_open

0 1 17.40 330 -6.60
1 2 3.20 350 -23.96
2 3 10.70 020 -14.07
3 4 12.90 070  0.44

0 a 13.80 045 -12.13
a b 7.80 021  -7.37
b c 15.00 340  -1.15
c d 4.35 350 -21.55

*END normal_open

*BEGIN normal_closed

*equate 4 d

0 1 17.40 330 -6.60
1 2 3.20 350 -23.96
2 3 10.70 020 -14.07
3 4 12.90 070  0.44

0 a 13.80 045 -12.13
a b 7.80 021  -7.37
b c 15.00 340  -1.15
c d 4.35 350 -21.55

*END normal_closed

*end divingtest