Hi, 1. Why does the decode on the rhs of ASV show Vis: 9999 Meters, 15 SM? 15SM is 24140 meters. Should it show >9999? In this case the relevant metar was showing 15 SM. 2. What is the logic used to determine vis when a metar actually reports >9999 or CAVOK?3. I'd also be interested to know how ASV determines cloud tops?(for info I am a retired forecaster)Mervyn

Hi,1. >9999 will not be used, just 15SM2. >9999 and CAVOK are both reported as 10SM3. Based on air temp, conditions and a bit of randomness.Hope this helps,JimActiveSky Sales and Supporthttp://www.hifisim.com/images/asv_dev_team.jpg http://www.hifisim.com/images/asv_proud_supporter.jpg