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1. Adjusting a Traverse
Adjusting a traverse (also known as balancing a traverse) is used to distributed the closure error back into the angle and distance measurements.
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Summing the latitudes and departures for the raw field traverse:
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| Figure E-1 Loop Traverse Misclosure |
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On an adjusted (balanced) traverse:
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| Figure E-2 Adjusted (Balanced) Loop Traverse |
The condition for an adjusted traverse is that the adjusted Lats and Deps sum to 0.00. As with other survey adjustments, the method used to balance a traverse should reflect the expected error behavior and be repeatable. Table E-1 lists primary adjustment methods with their respective advantages and disadvantages.
| Table E-1 | |||
| Method | Premise | Advantage | Disadvantage |
| Ignore | Don't adjust anything. | Simple; repeatable | Ignores error |
| Arbitrary | Place error in one or more measurements | Simple | Not repeatable; ignores error behavior |
| Compass Rule | Assumes angles and distances are measured with equal accuracy so error is applied to each. | Simple; repeatable; compatible with contemporary measurement methods. | Treats random errors systematically |
| Transit Rule | Assumes angles are measured more accurately than distances; distances receive greater adjustment. | Simple; repeatable; compatible with older transit-tape surveys. | Treats random errors systematically; not compatible with contemporary measurement methods. |
| Crandall Method | Quasi-statistical approach. Angles are held and errors are statistically distributed into the distances. | Allows some random error modeling; repeatable. | Models only distance errors, not angle errors. |
| Least squares | Full statistical approach. | Allows full random error modeling; repeatable; can mix different accuracy and precision measurements; provides measurement uncertainties. | Most complicated method |
The Compass Rule works sufficiently well for simple surveying projects and is the one we will apply.