Surveying
Transit Rule Traverse Adjustment
Summary
The Transit rule adjusts a traverse by distributing the easting misclosure in proportion to the absolute departure of each leg and the northing misclosure in proportion to the absolute latitude. It assumes angles are more precise than distances. Applied to the same loop as the Bowditch example, it also closes exactly but moves points differently, by up to 12 mm in northing.
Definition
Transit rule: a traverse adjustment in which each departure is corrected by −fE·|ΔEi|/Σ|ΔE| and each latitude by −fN·|ΔNi|/Σ|ΔN|.
- Correction ∝ |ΔE| and |ΔN|
- Assumes angles more precise than distances
- Undefined if Σ|ΔE| or Σ|ΔN| is zero
- Preserves bearings better on diagonal legs
Formula
Here fE and fN are the misclosures (computed minus known), and the sums run over all legs. The method was designed for transit-and-tape surveys, where angles measured with a transit were relatively better than taped distances.
When the Transit rule is appropriate
Use it only when you have reason to believe distances are the dominant error source, or when a client specification explicitly requires it. For total station traverses the Bowditch rule or a least squares adjustment is normally more appropriate.
A practical limitation: a leg that runs exactly north–south has zero departure and receives no easting correction, and if every leg had zero departure the rule would be undefined. GeoCAD Bridge reports an error in that case rather than dividing by zero.
Common mistakes
- Choosing Transit because it “moves points less”: the result depends on geometry, not on quality.
- Forgetting the absolute values, which makes corrections cancel.
- Applying it before balancing angles.
Worked example
Same balanced loop as the Bowditch example (start A = 5000.000 E, 3000.000 N):
| Leg | Azimuth | Distance (m) | Departure ΔE (m) | Latitude ΔN (m) |
|---|---|---|---|---|
| A–B | 26°10′00″ | 285.10 | +125.724 | +255.882 |
| B–C | 104°35′00″ | 610.45 | +590.783 | -153.704 |
| C–D | 195°30′00″ | 720.48 | -192.540 | -694.276 |
| D–A | 318°29′30″ | 790.55 | -523.920 | +592.011 |
| Sum | 2406.58 | +0.047 | -0.088 |
Σ|ΔE| = 1432.968 m and Σ|ΔN| = 1695.873 m. The corrections and adjusted coordinates are:
| Leg | Corr. ΔE | Corr. ΔN | Adj. ΔE | Adj. ΔN | Point | Easting (m) | Northing (m) |
|---|---|---|---|---|---|---|---|
| A–B | -0.004 | +0.013 | +125.720 | +255.895 | B | 5125.720 | 3255.895 |
| B–C | -0.019 | +0.008 | +590.763 | -153.696 | C | 5716.484 | 3102.199 |
| C–D | -0.006 | +0.036 | -192.546 | -694.240 | D | 5523.938 | 2407.959 |
| D–A | -0.017 | +0.031 | -523.938 | +592.041 | A | 5000.000 | 3000.000 |
| Point | Bowditch E | Transit E | ΔE (mm) | Bowditch N | Transit N | ΔN (mm) |
|---|---|---|---|---|---|---|
| B | 5125.719 | 5125.720 | +1.4 | 3255.892 | 3255.895 | +2.9 |
| C | 5716.490 | 5716.484 | -6.0 | 3102.210 | 3102.199 | -11.5 |
| D | 5523.936 | 5523.938 | +1.7 | 2407.960 | 2407.959 | -1.8 |
FAQ
Is the Transit rule more accurate than Bowditch?
Neither is “more accurate” in general. Each is optimal only under its own precision assumption. For modern total station data, Bowditch or least squares is usually the better model.
Why does a north–south leg get no easting correction?
Its departure |ΔE| is zero, so its share of Σ|ΔE| is zero. The whole easting misclosure goes to the other legs.
Can I switch between Bowditch and Transit in GeoCAD Bridge?
Yes. The Traverse Adjustment tool lets you choose either method and re-run the adjustment on the same observations so you can compare results.
Related tools and articles
Tools
- Traverse AdjustmentBowditch and Transit adjustment with closure report.
- Survey CalculatorsInverse, area, intersection, resection and more.
Articles
- Bowditch Rule (Compass Rule) Traverse AdjustmentThe Bowditch rule, also called the compass rule, adjusts a closed or link traverse by distributing the misclos…
- Traverse Adjustment: Complete Guide for SurveyorsA traverse adjustment turns measured angles and distances between control points into a consistent set of coor…
- Least Squares Adjustment for SurveyorsLeast squares adjustment finds the coordinates that minimize the weighted sum of squared observation residuals…
- Traverse Precision Ratio (Relative Precision)The precision ratio of a traverse is its total length divided by its linear misclosure, written as 1:N. A loop…
References
- Ghilani, C. D. & Wolf, P. R. Elementary Surveying: An Introduction to Geomatics, 15th ed., Pearson, 2018 (traverse computations and adjustments).
- Uren, J. & Price, W. F. Surveying for Engineers, 5th ed., Palgrave Macmillan, 2010.
- Ghilani, C. D. Adjustment Computations: Spatial Data Analysis, 6th ed., Wiley, 2017.
Cite this page
GeoCAD Bridge. “Transit Rule Traverse Adjustment.” GeoCAD Bridge Knowledge Center, updated 2026-10-05. https://www.geocadbridge.com/knowledge/survey-transit-rule/