Several people here seem intent on bashing me as if I am speaking heresy for calling Lake Pleasant an altitude dive. I think that I have qualified my comments sufficiently & I’ll even go so far as to say that I think my comments have been pretty much correct.
I’m not going to single out individuals who made specific comments because I don’t want to be argumentative. I will, however, try one last time to state my position more clearly.
When I dove in that area, I was diving under the instruction of the US Navy Dive Manual. I no longer have access to the hard-copy of the older version of that manual that I used at the time, but I was able to find public unclassified access to the current version - Naval Sea Systems Command > Home > SUPSALV > 00C3 Diving > Diving Publications
If you look at table 9-4, you may notice that SLED corrections are to be made at altitudes of 2,000 feet or more, even for very shallow dives and for dives to 150' or more, altitudes as low as 1,000 feet require a correction. As I remember Lake Pleasant, the roads leading in & out of there went up from the water. If the water was at 1,700’, then I think there was a pretty good chance that I hit 2,000' feet before I left the park. Regardless if I then went to Prescott or Mesa afterwards, the fact that I hit 2,000' one time, means that if I am following the book correctly, an altitude correction was indicated, even for a dive to as little as 10'. As was already stated by another, if I then went way up the hill to some place like Flagstaff, the altitude would be considerably more. In that case, a more substantial correction would be needed.
It may be common practice to dive that spot without taking altitude into consideration. The current tables & algorithms may have enough safety fluff built into them to allow you to ignore that detail without penalty if you leave the park & go to Phoenix, rather than Flag or the Snow Bowl. Altitude may not have been a factor in this incident. That does not mean that the dive is not correctly identified as being an altitude dive. ...at least if you believe the US Navy definition of the term.
I’m not going to single out individuals who made specific comments because I don’t want to be argumentative. I will, however, try one last time to state my position more clearly.
When I dove in that area, I was diving under the instruction of the US Navy Dive Manual. I no longer have access to the hard-copy of the older version of that manual that I used at the time, but I was able to find public unclassified access to the current version - Naval Sea Systems Command > Home > SUPSALV > 00C3 Diving > Diving Publications
If you look at table 9-4, you may notice that SLED corrections are to be made at altitudes of 2,000 feet or more, even for very shallow dives and for dives to 150' or more, altitudes as low as 1,000 feet require a correction. As I remember Lake Pleasant, the roads leading in & out of there went up from the water. If the water was at 1,700’, then I think there was a pretty good chance that I hit 2,000' feet before I left the park. Regardless if I then went to Prescott or Mesa afterwards, the fact that I hit 2,000' one time, means that if I am following the book correctly, an altitude correction was indicated, even for a dive to as little as 10'. As was already stated by another, if I then went way up the hill to some place like Flagstaff, the altitude would be considerably more. In that case, a more substantial correction would be needed.
It may be common practice to dive that spot without taking altitude into consideration. The current tables & algorithms may have enough safety fluff built into them to allow you to ignore that detail without penalty if you leave the park & go to Phoenix, rather than Flag or the Snow Bowl. Altitude may not have been a factor in this incident. That does not mean that the dive is not correctly identified as being an altitude dive. ...at least if you believe the US Navy definition of the term.