Real-time measurements of tide height

LaRea

If you deal with shallow tidal water in or near your marina, you might find this interesting:  I recently installed a system that measures water depth and posts real-time results live on the web for all to see.

It's a nifty toy, but it's really a boating safety device.  Tide prediction tables do not account for wind and rain, which can drastically affect water levels.  With a real-time tide monitor, I can check the depth via cell phone while underway, and know exactly whether there's enough water for my boat to get back into the marina.  

Check it for yourself:

http://mountvernonyachtclub.com/tides.html

One chart shows water depth, and the other shows air temperature.  The current reading is at the far right, and the rest of the chart shows history over the past three days.  

As I'm writing this, we've had extremely low tides a couple days ago because of a steady, strong wind from the northwest.  There was no navigable water within a half-mile of my marina, because the tide went out, and the wind kept it from coming back in.  Tide tables would not be able to predict these fluctuations.  

The system also measures air temperature.  We had 20s yesterday, and high 30s now. 

If anyone is interested in building their own device, let me know and I'll post details.  I built it from off-the-shelf components.  Total cost was around $500. 

LaRea

Here's a screen shot of the display.

LaRea

You could say that!  I calibrated the tide monitor to the mean depth in the channel that leads into my marina.  When it reads deeper than 2 feet, I can navigate the channel in my 370.  This week, we had readings of -0.5 feet, meaning the channel was dead empty!  It usually happens a couple times a year.

Dream_Inn

Definitely very interesting.  Where I keep my boat, there are maybe a dozen of us that have to be concerned with water level to fit under a bridge to get back to our marina.   Basically, there is a board that marks the spot where if the water is under it, I can go thru, if not, I may be able to go the "back" way.  The other way is around the island and thru a shallow area, but is ok if the tide is high (which is when you can't fit under the bridge).  For me, it'd be nice to know before I get to the bridge, whether I can fit under it or have to go around (to save time & gas).  Something like what you have would be great, but even something as simple as a float that opens/closes at that specific height & then post it.  I had thought about putting some yellow paint on a marker in the river that would indicate the level (if I see it, I can go under, else around), obviously it'd be down low on the piling by the water, not messing anything up.

LaRea

I know the marina you're talking about.  You're right, it would be useful there!

The system itself is pretty simple - an ultrasonic sensor, a controller board, and a wifi interface for web access, plus a battery backup. All off-the-shelf stuff, with no moving parts.  It required a bit of geek-power to figure out how to hook everything up, and also some boater creativity to build it into a weather-proof box.

One challenge was figuring out where to mount it.  The ultrasonic sensor looks directly down at the water and measures the distance to the surface.  It needs an unobstructed path where nobody will hang wet carpets on it, dock a boat under it, or whatever.  It also needs electrical power.  

Most of the basic info is on www.iobridge.com.  

Michael T

LaRea, thank you for a very good perspective. Your information is not only fascinating but herewith ends my whining when the water level at my slip goes below 5 feet! MT

LaRea

NOAA doesn't have a measurement station near my marina, so I built my own.  But many boaters can use NOAA's data directly.

For example, the Annapolis station:

http://tidesandcurrents.noaa.gov/stationhome.html?id=8575512