Quote:
Originally Posted by SDfan
Can anyone explain to me why the city is rescinding the 500ft height limit downtown in the next building code update? At the last city Land Use & Housing committee meeting, staff presented the removal of the height limit from the code. It passed out unanimously.
Check out the video link below and go to 1:13:13 to hear the staffer explain.
http://sandiego.granicus.com/player/...&redirect=true
I asked a avi friend what's up, and he said this:
"So the wide horizontal length across the approach path was to not obstruct the instruments required for an aircraft to land when theres inclement weather said equipment is at each end of the runway at most airports.
Thats changing. Most aircraft now are using GPS for their approaches which doesnt require the wide berth horizontally across the approach path due to its exact precision provided.
So as this antiquated equipment transitions out if you will, that horizontal field will shorten in nature across the approach path. So in essence, you could see more mid-hi rises north of the 5 closer to the approach path.
But it'll still depend on its actual location of the project because the airport has hilly terrain on either side as you know, and that presents separate problems that i wont bore you with!" |
To get a little clarity here, the city is *not* removing the 500' height limit everyone talks about, as measured from ground level to the highest architectural point. It's removing another 500' height limit, one measured from sea level to the highest architectural point.
As I've explained before, the first height limit is set at the state level by Caltrans so the city can't change it, but the city also has its own height limit at 500' above sea level. So if you built a tower on a hill 30' above the harbor, it could only be 470' from street level to rooftop. I don't really know what the reasoning was for setting it up, maybe in the pre-GPS days they were afraid of survey errors? In any case the city has already given out exemptions, the Pinnacle towers are 520' above sea level. The gains will be limited to an extra 20'-30' feet, while still being below 500' above the ground.
Your friend is on the right track with his thinking, but he's forgetting that airports also have to plan for low precision GPS approaches in addition to high precision ones, and the clear zone for a low precision GPS approach is even wider than you need for a radio wave based localizer.
Here's a comparison using KSAN. The pink is the clear zone for a non-precision LNAV GPS approach, and the yellow is the clear zone for a good old fashioned localizer.
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