There are three ways to enter the Line Angle value of a measurement,

• Manually, by typing the angle’s value.
• Using the Smartphone’s angle sensors.
• Using a Trolling Angles Autocline device.

Most people will use the Smartphone.

Select the Smartphone option, which will use the smartphone sensors to keep the Line Angle field updated to the angle of the phone with respect to horizontal.

Measure the angle of the line with respect to horizontal with the smartphone. This is a convenient and automatic way to measure and record the angle with no additional equipment or manual data entry.

The figure above shows how this is performed by holding the smartphone (not over the water!) parallel to the line and the boat’s travel motion.  Visually align the edge of the device to the portion of the fishing line evident above the surface of the water.

You do not need to place the smartphone directly on the line to measure its angle. The rod can be deployed in a normal fishing position, and you can hold the smartphone inside the boat, as long as you hold the edge of the smartphone parallel to the line.

While the device and the line are aligned, press the Done button to save the displayed line length and line angle, or the All Done button to return to the calibration page.

Trolling Angles also supports an external device, the Trolling Angles Autocline, to measure line angles.

Alignment

Align the Smartphone Carefully with the Fishing Line.

To get an accurate angle measurement, it is critical that the smartphone body is parallel with the fishing line.  If the smartphone is not exactly aligned with the fore-and-aft direction of the line, the measured angle of the visible line will be different than the line’s actual angle, and therefore the calculated depth will be different than the lure’s actual depth.

It is not always easy to see the exact alignment of the line, especially when the rod tip is out to the side of the boat.  On a calm day, trolling in a straight line, your line is aligned with the boat, and you can then align the phone with the centerline of the boat. However, if the wind is blowing your boat sideways at all, the trolling line will be at an angle to the boat’s centerline, and you probably do not have a good perspective to see the exact trolling line direction.

The Alignment Aid

You can use the graphical Smartphone Alignment Aid while taking measurements. It shows two lines, one representing the alignment of the phone, and another showing the alignment of the trolling line.  When the two lines are overlapped, the phone is aligned with the trolling line.  The trolling line direction is deduced from the GPS and the water current correction.  The phone alignment is measured using the phone’s magnetic compass, corrected to true north according to magnetic declination at your location.  The GPS is trustworthy when the boat is moving, but the compass and your current correction may not be fully accurate, so use common sense whether to use the aid or to eyeball the phone and trolling line yourself. In slack water without current and in an aluminum, fiberglass or wooden boat, the alignment aid will give fairly good results.

The Autocline is always aligned with the trolling line, so the alignment aid is not needed or useful when using the Autocline.

Multiple Measurements

This measurement screen is where you can inactivate individual measurements, delete them permanently, or easily add new measurements.

When multiple measurements are taken for the same line length, they are all shown in the measurement screen along with their mean (average) and standard deviation. The average value is shown in the Calibration screen and is used to calculate the depth curve.

By averaging multiple measurements, the app reduces the amount of measurement error and improves accuracy. It also allows you to easily identify and eliminate poor measurements (outliers). The measurements are shown in order by time, with the earliest measurements first. This allows you to notice whether the line angle is increasing or decreasing as you are measuring, which could indicate that the lure is still in the process of settling in to its stable position.

Ultimately, the standard deviation values allows one to calculate the statistical precision of the whole configuration. As a very rough rule of thumb, if the standard deviation of the angles at each line length is less than 1.0, one can expect that there is a reasonable likelihood that the depth curve is accurate to one foot.

Save and Repeat

The average of the calibration data pairs, consisting of the line length and angle, are added to the calibration data. The depth of the lure at all line line length measurements is also calculated and displayed, using the new measurements along with all the existing measurements.

Release or recover additional length of line with the reel, and repeat measuring and recording the line length and line angle multiple times until a reasonable maximum desired length of line has been measured, and a reasonable number of data pairs have been recorded.

Press the Back arrow or the smartphone’s Back button to return to the Calibration Screen.