Speed Reading on Garmin

[tborcher]

I have an RT 21. Does the Garmin gets its statute miles per hour speed reading from the transducer? Or from a cable attached to the engine? Or somewhere else?

 

[BradOwens]

From the GPS position data. It calculates the time to move from one location to another (It's accurate enough to only need a few feet of movement) and converts that to speed.

 

[bob daily]

tborcher: To answer your question ,somewhere else! The speed on your Garmin is computed from information received from satellite. Lots of good info about gps on the internet.
Hope this answered your question. Bob

 

[tborcher]

Thanks for taking the time to respond to my question. For some reason the speed reading isn't showing up on my screen like it used to. All the other Garmin gps related info seems to be up and running (direction, depth, mile posts). I thought maybe some wire had gotten disconnected. Guess not. I'll do more exploring when I get back on the boat.

 

[knotflying]

tborcher: To answer your question ,somewhere else! The speed on your Garmin is computed from information received from satellite. Lots of good info about gps on the internet.
Hope this answered your question. Bob

Keep in mind that the speed you see on your GPS is over ground. It is not speed over water. The difference may be important to those fishing and requiring a specific trolling spreed. Also, in many speed zones they reduce speed for safety, but at times to also avoid wake. With a high current going against you it will result in a ground speed plus the current you are going against. Example: Speed over ground at 6 MPH against a 2 MPH current will result in 8 MPH over water. Not a big deal, but important when trolling for fish or trying to minimize wake.

 

[bob daily]

As Mr.Knotflying noted the difference between ground speed and water speed is sometimes confusing, and will depend on wind and current. To get a accurate reading you can use a trolling speed indicator, manufactured by Luhr Jensen co. It's easy to set up and use, cost is low and will give you a accurate speed over water when trolling. A photo of one being used is in my album. Bob

 

[jagizzi]

When you say that the speed reading isn't showing up do you mean that the space where the speed is reported is gone, or are you seeing dashed lines in the space where speed used to be?

Where are you used to seeing your speed reported?