2. Angular Misclosure
Angular misclosure is the difference between the measured angles' sum on a traverse and the angle condition for the traverse configuration.
The amount of allowable angular misclosure is dependant on the survey purpose. The limits are generally expressed as an Error of a Series:
|C: Allowable misclosure, seconds
k: expected error in each angle, seconds
n: number of angles
Traditional formal standards from the FGCS Standards and Specifications for Geodetic Control Networks are:
What is the allowable angular misclosure for a five-sided traverse if it is to meet Second Order Class II standards, Figure B-5?
From Table 1, k = 4.5". Substituting into Eqn (B-4):
Because this is a five-sided loop traverse, using Eqn (B-1) the angles should sum to:
Therefore, the total should be in the range 539°59'50" to 540°00'10".
Informal standards can be created which reflect equipment, experience, conditions, project needs, etc.
A control network is to be established for a construction project. Sight distances will be relatively short (under 300 ft) so measuring angles consistently will be a challenge. Testing under these conditions, our survey crew was able to measure an angle to a consistency of ±0°00'12". For this project, we will use an allowable misclosure of: