Compass (Bowditch) Rule

c_{lat, i} = - E_{lat} \frac{ℓ _{i}}{P} c_{dep, i} = - E_{dep} \frac{ℓ _{i}}{P}

Distribute latitude and departure misclosures in proportion to side lengths. P is the perimeter. Transit rule uses |lat| or |dep| instead of length. Apply after computing Ec and checking precision.

$E_{lat}$: Latitude misclosure
$ℓ_{i}$: Length of side i
$P$: Perimeter

Step-by-step solved example

Σlat error Elat=+0.40 ft, P=400 ft, side ℓ=80 ft. Latitude correction on that side?

Compass (Bowditch) rule distributes closure error by length.

1. Rule
c= −0.40 × 80/400 = −0.080 ft.
$c = - 0.080 ft$

Answer: −0.080 ft on that latitude

10 practice questions

0/10 correct

1.Compass rule weights by

2.Sum of lat corrections equals

3.Transit rule is better when

4.A longer side gets

5.After adjustment, Σlat and Σdep should be

6.If Elat=0 you still

7.P is

8.Least-squares adjustment is

9.Correction has the opposite sign of the misclosure so that

10.Precision 1:5000 means Ec/P =