Chapter 5 — CLOUDS AND VISIBILITY 



209.214 

 Figure 5-2. — Sample daytime visibility marker chart. (D = distance to object, H = height of object 



in feet.) 



determining the visibility in the sector in 

 which the instrument is installed provided 

 the observer determines that the visibility is 

 uniform throughout that sector. This use is 

 dependent upon the transmissometer value being 

 less than 2 miles. During other visibility 

 conditions and in other sectors, determine 

 the sector visibility by visual observations 

 when necessary. 



Variable Visibility 



Variable visibility refers to a condition 

 in which the visibility varies by one or more 

 reportable values during the period of obser- 

 vation. The average of all observed values 

 is used as the visibility. The limits of varia- 

 bility must be reported when the average is 

 less than 3 miles. 



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