## 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:

Equation B-4 | ||

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:

Table B-1 |
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Angular Misclosure |
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Order |
Class |
k (sec) |

First | - | 1.7 |

Second | I | 3.0 |

II | 4.5 | |

Third | I | 10.0 |

II | 12.0 |

*Example*

What is the allowable angular misclosure for a five-sided traverse if it is to meet Second Order Class II standards, Figure B-5?

Figure B-5 Allowable Misclosure |

From Table 1, k = 4.5". Substituting into Equation B-4:

Because this is a five-sided loop traverse, using Equation 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.

*Example*

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: