This seems to be a pretty comprehensive coastal navigation text. http://books.google.com/books?id=qN...v=onepage&q=navigation bridge heights&f=false
Mast Clearance
- Thread starter mrmarch
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All vertical clearances on charts in the U.S. are shown as distance above mean HIGH water, not mean low water. (I just studies this for the Coast Guard OUPV exam).
Agaliha
Agaliha
Right from the Source
You should be fine but I'm not sure I would not go at high tide just to be safe
http://www.nauticalcharts.noaa.gov/mcd/learnnc_bridge.html
http://www.nauticalcharts.noaa.gov/mcd/learnnc_bridge.html
Charted Bridge Clearances
Vertical bridge clearances on charts are referenced to Mean High Water in tidal areas. Therefore if the existing height of tide is below MHW, there will be greater clearance. If the existing height of tide is greater than MHW, there will be less clearance. The USCG provides bridge clearance information to NOAA.
Chuckbear thanks for the clarification. I wasn't sure if low steel included the steel for the lights or not. They appear to hang down 18" to 2 feet. I took a friend's boat down the Tenn-Tom from Kentucky Lake and we had some bridge clearances that calculated about 2 inches clearance to the antenna - and they were "flat" steel bridges. The arch bridges were much easier to understand and we figured they were measured to the lowest part near the supporting column. On the flat bridges we cleared with much more than the 2 inches and debated all the way to Punta Gorda where the measurement was to on that type - many of which are listed as 52 feet on the Tenn-tom. Your real working knowledge is very nice to know!
Thanks everyone. The Coast Guard station is about 300 feet from the Matanza bridge,
I think I'll go talk to them and see what they have to say. I do have another question?
If the bridge clearance is measured from the HMW, but all charts are marked from LMW. How does one find out what the HMW is? Is this something I need figure out myself by looking at tide charts for the area?
I think I'll go talk to them and see what they have to say. I do have another question?
If the bridge clearance is measured from the HMW, but all charts are marked from LMW. How does one find out what the HMW is? Is this something I need figure out myself by looking at tide charts for the area?
The tide charts give you the mean range of the tides at each location.
http://co-ops.nos.noaa.gov/tides06/tab2wc3.html
edit to paste link
http://co-ops.nos.noaa.gov/tides06/tab2wc3.html
edit to paste link
Rich's illustration is a bit of an exaggeration, he apparently has an issue with Florida, but it does have some value. If you take his red line and move it up to the lowest point within whatever the channel width is, then that will be the measurement for the tide boards, and not just in the state of Florida. This is the Federal requirement for any bridge. Chuck
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