Page 57 - Green - Maritime Archaeology: A Technical Handbook. 2nd ed

B
B A
A
C
D 12
C
B
D
A
C
A
D 34
D
BB
B
C
A
C
D
A
C
D
Figure 3.8 Here are six examples showing the strength of resection by showing how the angle of resection gives the best fix when the arc crosses at right angles. (From Hydrographer of the Navy (1965). Admiralty Handbook of Hydrographic Surveying, HMSO, London.) Note, in 1 and 2 the receiving angles are the same and 1 is an excellent fix, but in 2 there is a circular or no fix. 3 is a good fix because the position circles cut at good angles. 4 shows the condition where a small change in the angle BDC will have a large effect on the position of D. 5 and 6 are also good fixes.