What criteria is used to define or measure visibility?

Print
Email
|

by Jeff Renner

Bio | Email | Follow: @Jeffrennerwx

KING5.com

Posted on April 20, 2012 at 5:42 PM

What criteria is used to define or measure visibility?

During daylight hours, visibility is measured by how far you can see a prominent dark object on the horizon against the sky. At night, it's the distance you can see a moderately intense but unfocused light source. In other words, NOT a spotlight. For aircraft, it's the maximum distance along the runway that runway lights are visibile. That can be measured by an observer or by special equipment.

Print
Email
|