The Trolling Angles Current Gauge measures the water current’s speed and direction by taking into account the GPS speed and direction, and the compass heading and line angle of a known rig which has been calibrated for different speeds.

Invoke the Current Gauge

To start the Current Gauge from the Main screen,

• press the Gauge button to show the Gauge Setup screen,
• enter the gauge name and press the search button
• choose the Current Gauge tab

Or, from the Calibration List,

• choose a calibration that is part of a Gauge,
• choose the Gauge tab to show the gauge tabs and screens,
• choose the Current Gauge tab

Use the Current Gauge

Deploy the trolling rig at any boat speed and line length in the range of the gauge’s calibrations, and enter the Line Length.

Select the Start button to turn on the smartphone GPS and angle sensors, and measure the line angle of the trolling line with the smartphone. This will also measure the compass orientation of the trolling line.

Trolling Angles will compare the line angle to the angles of the gauge’s calibrations at the given line length, and will interpolate to determine the speed through water.

Three Velocity Vectors

The measured speed and direction through water is compared to the speed and direction over ground from the GPS, to give the speed and direction of the current.

This information is presented as numerical values, and as graphical vectors. Note that there are three related velocity vectors, each with

• a direction, in degrees relative to true north
• and a speed, represented by the length (magnitude) of the vector.

The three velocity vectors are

• SOG, (Speed Over Ground) in Green, with a boat icon is obtained directly from the GPS.
• STW, (Speed Through Water) in Blue, with a lure icon, is obtained by your line angle measurement and the smartphone compass as it is aligned with the line. This is the velocity apparent to the lure and line.
• Current in Red. Since the total SOG is the vector sum of the Current and the apparent STW, the Water Current is calculated by subtracting the STW vector from the SOG vector.

Note that you can visualize this by mentally moving the current vector so that it .starts at the end of the STW vector, to result in the SOG vector.

Save and Use the Current Velocity

When you are satisfied that you have determined a good smartphone alignment with the line, press the Stop button to freeze the screen, and then if the values for the three vectors seem reasonable, press the Save button to save the Current vector. This saves it as a permanent preference for filling the current correction velocity used in Trolling screens.

While trolling, turn on the GPS and Current switches, and control your boat speed so that the STW value in the trolling screen matches the defined speed of your rig calibration. Then, the lure and line will experience the proper apparent speed, and your actual line will accurately match the depth curve of the app.