FW08 — Closed Traverse Survey Using a Total Station

Learning Objectives

  • Set up, center, level, and orient a total station at successive traverse stations.
  • Record station, backsight, foresight, prism-height, angle, and EDM information completely.
  • Measure a closed traverse with redundant angular and distance observations.
  • Check angular closure before coordinate reduction.
  • Compute latitudes, departures, linear error of closure, and relative precision.
  • Apply the Compass/Bowditch Rule to an accepted traverse and compute adjusted coordinates.

Total Station Does Not Eliminate Survey Control

A total station automates angle and distance measurement, but the survey still depends on correct station identity, centering, backsight orientation, prism height, target selection, coordinate reference, and independent closure checks. Fast electronic observations can produce fast wrong results when setup metadata are incomplete.

Required Setup Information

Record for Every Occupation

Field Procedure

Closed Total-Station Traverse

  1. Reconnoiter and monument a closed station sequence with clear intervisibility.
  2. Occupy the starting station and perform precise centering and leveling.
  3. Enter or record the station coordinate/reference information and instrument height.
  4. Orient to the assigned backsight using the specified azimuth or known-coordinate method.
  5. Observe the foresight angle/direction and EDM distance to the next station.
  6. Repeat the angular observation or face set when required.
  7. Move to the next station and repeat the occupation record, including instrument and prism heights.
  8. Continue until the traverse closes at the starting control.
  9. Check angular closure and obvious distance/target errors before leaving the site.
  10. Reduce accepted observations to coordinate components and evaluate linear closure.

Theoretical Interior-Angle Sum

Expected sum for an n-sided closed polygon.

∑θtheoretical=(n−2)180∘\sum \theta_{theoretical}=(n-2)180^\circ

Angular Misclosure

Difference between observed and theoretical angle sums.

eθ=∑θobserved−(n−2)180∘e_\theta=\sum\theta_{observed}-(n-2)180^\circ

Latitude and Departure

Coordinate components for horizontal length L and azimuth A.

Lat=Lcos⁡ADep=Lsin⁡A\text{Lat}=L\cos A \qquad \text{Dep}=L\sin A

Linear Error of Closure

Magnitude of the unadjusted coordinate misclosure.

LEC=(∑Lat)2+(∑Dep)2LEC=\sqrt{(\sum \text{Lat})^2+(\sum \text{Dep})^2}

Relative Precision

Traverse perimeter divided by LEC.

RP=∑LLECRP=\frac{\sum L}{LEC}

Bowditch Adjustment

When to Adjust

Adjustment is performed only after the field observations pass the assigned acceptance criteria. Adjustment distributes an accepted residual misclosure; it does not rescue blunders, wrong station IDs, incorrect prism constants, or failed setups.

Bowditch Latitude Correction

Distributes latitude misclosure proportional to course length.

CLat,i=−(∑Lat)Li∑LC_{Lat,i}=-\left(\sum Lat\right)\frac{L_i}{\sum L}

Bowditch Departure Correction

Distributes departure misclosure proportional to course length.

CDep,i=−(∑Dep)Li∑LC_{Dep,i}=-\left(\sum Dep\right)\frac{L_i}{\sum L}

Adjusted Components

Applies Bowditch corrections to each course.

Lati′=Lati+CLat,iDepi′=Depi+CDep,iLat_i'=Lat_i+C_{Lat,i}\qquad Dep_i'=Dep_i+C_{Dep,i}

Coordinate Propagation

Computes the next station from adjusted components.

Ni+1=Ni+Lati′Ei+1=Ei+Depi′N_{i+1}=N_i+Lat_i'\qquad E_{i+1}=E_i+Dep_i'

Electronic Files Supplement the Field Record

Instrument job files, coordinate exports, and downloaded observation files should be retained when assigned, but they supplement rather than replace the field-book record of station identity, setup metadata, checks, and site conditions.

Coordinate Reference

The report must identify whether coordinates are assumed/local, grid, or tied to a defined geodetic system. An arbitrary classroom coordinate such as N = 1000 m, E = 1000 m must be labeled assumed local coordinates and must never be presented as GNSS or cadastral control.

Quality Control Before Leaving

Submission Timing

Fieldwork Data is due within the scheduled 3-hour class period. The Full Fieldwork Report is due on the next class meeting. FW00 remains authoritative for safety, raw-data integrity, naming, and submission requirements.

FW08 — Required Data Tabulation

Use this structure as the minimum field or research data table. Add columns when the activity requires more detail.

Setup / LineBacksightHorizontal angle / azimuthSlope distanceVertical / zenith angleHorizontal distanceΔNΔECoordinate
A → BRecordRecordRecordRecordReduceComputeComputeCompute B
B → CRecordRecordRecordRecordReduceComputeComputeCompute C
…ContinueContinueContinueContinueContinueContinueContinueClose to start

Also record instrument height, prism height, prism constant, station setup IDs, and the electronic/raw file name when data are exported.

FW08 — Grading Rubric

Award points according to the evidence shown for each criterion.

Total: 25 pts
CriterionFull-credit evidencePoints
Total-station setup and orientationCentering, leveling, backsight/orientation, prism setup, heights, and constants are correct and documented.5
Raw/electronic observation completenessAngles, distances, station IDs, setup metadata, and exported records are complete and traceable.5
Traverse closure and coordinate reductionAngles/directions, latitudes/departures or coordinate increments, LEC, relative precision, and coordinates are correctly computed.7
Adjustment and QA/QCRequired adjustment method is applied correctly, adjusted closure is verified, and tolerance decisions are documented.4
Report and technical plotRaw versus adjusted data, coordinate table, technical plot, metadata, units, and conclusions are professionally presented.4
Total25 / 25

Scoring guide: full credit for complete, technically correct, traceable evidence; reduce proportionally for minor errors, incomplete work, or weak documentation.

Key Takeaways
  • A total-station traverse is a control network, not just a sequence of electronic readings.
  • Angular closure is checked before coordinate adjustment.
  • LEC and relative precision describe the unadjusted linear closure.
  • Bowditch adjustment is applied only to an accepted traverse and preserves a clear distinction between raw, computed, corrected, and adjusted data.