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E4004 Survey Computations A. Bowditch Adjustment. Traverse Adjustment. Bowditch Rule based on the assumption that angles (bearings) are observed to the same degree of precision that distances can be measured. Bowditch Rule from E0007. Adjust the angular misclose

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e4004 survey computations a

E4004 Survey Computations A

Bowditch Adjustment

traverse adjustment
Traverse Adjustment
  • Bowditch Rule
    • based on the assumption that angles (bearings) are observed to the same degree of precision that distances can be measured
bowditch rule from e0007
Bowditch Rule from E0007
  • Adjust the angular misclose
  • calculate the misclose in position
  • adjust according to the formula

length of the current line

= latitude of the current line

= departure of the current line

= sum of the traverse line lengths

bowditch new method
Bowditch - New Method
  • Adjust the angular misclose
  • calculate the misclose in position
  • consider the diagram
  • AB’C’D’ is a traverse from A to D

C’

D’

B’

A

D

bowditch new method5
Bowditch - New Method
  • But the traverse coordinates of D’ are not the same as D
  • the misclose at D is D’D

C’

D’

B’

A

D

bowditch new method6
Bowditch - New Method
  • Let the traverse line lengths be 1, 2 and 3 as shown
  • The total length of traverse is 1+2+3=6

C’

3

D’

2

B’

1

A

D

bowditch new method7
Bowditch - New Method
  • In order to adjust the traverse such that D’ and D are coincident D’ would have to be corrected by a Brg and Dist equal to D’D

C’

3

D’

2

B’

1

A

D

bowditch new method8
Bowditch - New Method
  • according to Bowditch the correction at each intermediate point is proportional to the length of each separate traverse line over the total traverse length times the misclose

C’

3

D’

2

B’

1

A

D

bowditch new method9
Bowditch - New Method
  • In this example the correction at D’ must be

of the total misclose

  • Divide D’D into 6 parts

C’

3

D’

2

B’

1

A

D

bowditch new method10
Bowditch - New Method
  • The correction at B’ must be in the same direction but for a length proportional to 1/6 of the total correction

C’

3

D’

2

B’

1

A

BAdj

D

bowditch new method11
Bowditch - New Method
  • The correction at C’ must be in the same direction but for a length proportional to (1+2)/6 of the total correction

C’

3

D’

2

B’

1

CAdj

A

BAdj

D

bowditch new method12
Bowditch - New Method
  • The adjusted bearings and distances would form the lines as shown

C’

3

D’

2

B’

1

CAdj

A

BAdj

D

bowditch new method13
Bowditch - New Method
  • A close program can be used to calculate the adjusted bearings and distances and the adjusted coordinates

C’

3

D’

2

B’

1

CAdj

A

BAdj

D

bowditch new method14
Bowditch - New Method
  • Consider the triangle AB’B
  • Once the correction (D’D) is known both lines AB’ and B’B are known
  • The line AB can be calculated by closure

C’

3

D’

2

B’

1

CAdj

A

BAdj

D

bowditch new method15
Bowditch - New Method
  • From Badj draw a line parallel to B’C’
  • The bearing and distance BAdjC” are the same as for B’C’
  • The line C”Cadj is the correction relevant to this line i.e. 2/6 Corr

C’

3

D’

2

C”

B’

1

CAdj

A

BAdj

D

bowditch new method16
Bowditch - New Method
  • Close the triangle BAdjC”Cadj and the adjusted bearing and distance BAdjCAdj is found

C’

3

D’

2

B’

1

CAdj

A

BAdj

D

bowditch new method17
Bowditch - New Method
  • Similarly, draw a line parallel to C’D’ from CAdj
  • The line D”Dadj is the correction relevant to this line i.e. 3/6 Corr

C’

3

D’

2

C”

B’

1

CAdj

A

BAdj

D”

D

bowditch new method18
Bowditch - New Method
  • Close the triangle CAdjD”Dadj and the adjusted bearing and distance CAdjDAdj is found

C’

3

D’

2

B’

1

CAdj

A

BAdj

D

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