Flawed closure procedures!

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Flawed closure procedures!

Postby pasurvey » Tue Jan 18, 2005 6:42 am

Field Genius 04 does not correctly report or adjust traverse. I ran a manually entered simple 3 legged travese and found the following:

Program assumes the initial measured backsight reading is absolute, when reporting precision it ignores this measured distance. On my trial it reported 1/14,374, but including the measured backsight it came out to 1/19,999.

A greater concern is the way the horizontal angles are adjusted. The turned closing angle is held absolute. On my simple traverse, adjustment is applied to the first two turned angles only and not the closing angle.

All measured legs and all turned angles of a traverse are part of that traverse and must be considered when reporting and adjusting.

Please fix it!
LP
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More Info Please

Postby Darcy Detlor » Tue Jan 18, 2005 9:17 am

How many fixed points were in your traverse?

If you are describing a box with 2 points fixed, then we are not going to move the fixed points, therefore the measured distance between the fixed points cannot be considered part of the traverse.

I am only guessing at this point, because your information does not fully describe what you are attempting to do.
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Postby pasurvey » Tue Jan 18, 2005 10:26 am

My example is a three leg closed loop traverse. All components of the traverse are measured forming a triangle.

occuppy 2
bs 1 by bearing (assumed n10e) measure angle and distance
manually enter 200.01 for distance 60°00'03" for horizontal angle.

fs 3
manually enter 199.98 for distance and 60°00''03" for horizontal angle.

occuppy 3
bs 2
fs 1 (4)
manually enter 199.98 for distance and 60°00''03" for horizontal angle.

occuppy 1 (4)
bs 3
fs 2 (5)
manually enter 199.98 for distance and 60°00''03" for horizontal angle.

Total measured legs of traverse 200.01+199.98+199.98=599.97'
Total measured angles 60°00''03"+60°00''03"+60°00''03"= 180°00'09"

FG04 reports
Total traverse 399.96 (assumed 199.98+199.98 )
Horizontal error 0.03' 180°58'44"
Angular error 0°00'09"
precision 1:14,374 (399.96/0.03=13,332 discrepancy due to rounding?)

precision calculation for close loop traverse 1:19,999 (599.97/0.03=19,999)

I think the key word is loop.

The overwhelming percentage of closed traverses done by me and my fellow surveyors in this area are loop.
LP
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Postby Darcy Detlor » Mon Jan 24, 2005 10:03 am

I am trying to enter the data as described but hit a snag.

You say setup on 2 with an assumed bearing of n10d east with a horizontal angle reading of 60d. Does this mean that you are not zeroing the instrument on the backsight? If not, then your shot to point 3 is also with a horizontal instrument reading of 60d so it is on top of 1?

Perhaps you could email me the fg files so I can see the project.
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Postby pasurvey » Mon Jan 24, 2005 12:55 pm

My goof, should be...

occupy 2
bs 1 by bearing (assumed n10e) measure angle and distance
manually enter 200.01 for distance, 0°00'00" for horizontal angle, (0 set).

I'll email the files.
LP
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Postby pasurvey » Sat Feb 26, 2005 5:40 am

Darcy,

I emailed the requested files back on January 24th. What's up?

LP
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Postby Jason Poitras » Mon Feb 28, 2005 4:57 pm

Hi,

The backsight point is held fixed and therefore doesn't move. So in your example the total length reported, is the total length you traversed around back to the original backsight. So this would amount to two traverse legs for a total distance of 399.960. The error of closure between points 4 and 1 is 0.028 @ 180°58'41" with a precision of 1 in 14374.

Currently FieldGenius does not perform a "text book" closed loop traverse which is what you're wanting it to do.
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Postby pasurvey » Thu Mar 03, 2005 5:01 am

Jason,

If you are going to assume that we are all doing closed traverses and not closed loop traverses then what about the closing angle not being adjusted? In a closed traverse you can hold your distance and position of your starting leg but you must adjust your turned angles, all of them. The closing angle is not magically golden.

If your are not using a
text book
then what book or reference are you using? I have several that I can provide you with.

Since this discovery I've stop using FieldGenius for boundary work and gone back to my other data collector. I would like to use FieldGenius for all my work. Is there a plan to structure it to a text book format?

Regards,
Larry Parks, PLS
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Traverse Closure

Postby T.M. Moretz » Thu Mar 03, 2005 6:05 pm

I reduce and adjust traverse files in my data collector for this very reason. I think that the Field Genius and the office software would benefit from an option for a classic "Text Book" closure routine - just like every other surveying software I can think of. Text books and all of their examples are a good thing. A great deal of what I know came from text books and I don't want to abandon what they taught me.
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Postby pasurvey » Thu Aug 04, 2005 2:37 am

Still looking for answers. Please respond. It appears that this problem also lives within your desktop software.
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See MSCAD 2005

Postby Darcy Detlor » Thu Aug 04, 2005 7:23 am

Hello,

The 2005 version of MSCAD has a "text book" closed loop traverse in it now. Due to popular demand, we re-wrote the "Closed Loop" method of computing the closure to accept the basic loop traverse that closes on the first setup.

The loop "floats" because you are starting and ending at the same point.

Basically the program looks for a shot from the last setup back to the first setup. If it finds one, then it has all the information it needs to compute a closure. You asked for it, and we modified it. Since it is different from the previous version there are small changes to the results because it is not closing onto the starting backsight point. If you liked the way it worked before you can also do that by choosing the "Open" method and entering in the information like the previous version.
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Postby pasurvey » Fri Sep 02, 2005 2:34 am

When will this feature be added to FieldGenius?
LP
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