FAQ

This is not obvious to everyone. Some assume that a line is nearly straight. Some have the first impression that a line has a trailing far end so that the line angle is steepest near the boat. In fact, a trolled line has a belly so that the line angle is steepest near the lure.

Surprisingly, changes in boat speed have no effect on the diving depth of an unweighted neutral or floating diving lure, if line length is not changed. This is because all balancing forces are proportional to the velocity squared.

• diving force of the lure
• lift force of the line
• drag force of the lure
• drag force on the line

So, the changes in these forces cancel out as velocity is changed.  Due to changing drag, the rig becomes more or less easy to pull through the water, but the force vectors maintain the same angle at all points of the line.

As speed is increased, the drag force of the lure, the drag force of the line, and the lift force of the line all increase proportionally to the velocity squared. However, there is no effect on the downforce caused by the weight of the lure. So, the increased lifting and drag forces cause a shallower line angle and depth as velocity increases.

As more line is released into the water, the total line lift force increases. At some point line lift equals the weight and diving forces of the lure. In the special case in which the rod tip is at the surface, any additional line released will stay at the surface, and the line and lure will not go deeper.

In the case in which the rod tip is elevated, the rod lifts the line too, and as more line is released, the longer submerged line provides more lift, and the rod provides less lift (and more horizontal pull) because the line angle  becomes more acute.

At any rate, the lure will not go any deeper than allowed by the balance of lift versus weight and diving force.

Note that for a sinking rig, depth can still be increased by reducing speed, but a floating/diving lure is not affected much by speed.

Yes.  Especially if the cannonball is not visible on your depth finder due to blowback, Trolling Angles can be useful to show the actual depth of a downrigger cannonball. The weight of a downrigger cannonball usually dominates the effect of cable drag and lift, so that the cable is close to vertical. When the angle of the cable is close to vertical, small changes of angle result in very small changes in the depth. As the rig is trolled faster, more drag does occur, and the effect is to create a bigger belly in the line and to raise the cannonball. Note that the deflection from vertical is greatest at the surface, but is still near zero near the cannonball, so the actual depth is greater than may be obvious based on the surface angle.

Yes. First, calibrate for your rig and terminal tackle without the planer board. Then, in the Trolling page, set the rod tip height to zero (0), and set the desired depth to obtain the line length at which you will attach the planer board, and then deploy the planer board.

In some trolling rigs, a large weight is placed on the line many feet from the end terminal tackle.  This can be accommodated in a straightforward way with Trolling Angles.

First, start measuring the angles of the portion of the line without the weight.  When you have let out enough line to attach the weight, take an angle measurement.  Attach the weight close to the rod tip.  Let out enough line to submerge the weight and take another measurement.

As you let out more line and take more measurements, the line profile graph will show a reverse bend in the line between those points near where the weight is attached, and Trolling Angles will fairly accurately model the actual line.

The analysis algorithm creates curve data for each segment of the line below the surface by accounting for the line above the surface and subtracting it from the total line length for every measurement.  You can see the joints where submerged line segments meet in the graph by turning on the Points option in the graph settings.

In general, the more length/angle measurements you take, within reason, the better, if those measurements are accurate. However, if measurements are inaccurate, or conflict with each other, they will cause errors in the analysis process. Because the app uses a reasonable curve fitting algorithm, measurements less than 10 feet apart will probably not lead to noticeably better results. And, of course, you need to take at least one measurement with a line length equal or greater than the maximum line length you will use while trolling.

Each separate segment is calculated by the app as an independent curve, which reflects the reality that the lift and drag coefficients change somewhat as the line’s angle of attack changes.

However, along a segment of 10 or 20 feet,  the coefficients don’t change enough to make much difference.

• Angle measurement. Your eyes are surprisingly good at lining up the smartphone with the line with good accuracy. However, in a pitching boat, or with poor light, line angles are sometimes hard to gather. It is important to hold the smartphone parallel to the boat’s direction of travel and to the line. If you have trouble, take several measurements and then inactivate or delete all but one consistent measurement.  The optional Autocline device can make angle measurements easier and more accurate.
• Speed control. You should try to keep your boat at the same constant speed while calibrating and while trolling.
• Direction control. If the boat changes direction while calibrating or trolling, the angles of the trolled line may change.
• Current.  A river current or tidal current can cause you to misunderstand the actual speed of the line and lure through the water, as a GPS shows speed-over-ground, not speed through the water.  Trolling Angles can help measure the  current’s speed and direction, and can correct for it while trolling.
• Curve Approximation. A variety of different algorithms and curve fitting techniques were evaluated during the development of the app.  A technique that models real world physics with an approximation to a smooth curve was chosen. With reasonably accurate measurements spaced at 10 feet each, almost any reasonable smooth mathematical function would lead to less error than the fish would notice.
• Mistakes.  The most common source of error is just user error, like manually entering the wrong line length or angle.
• External Factors.  There are some factors unrelated to the app to keep in mind while trolling.  Your depth-finder transducer is probably mounted a foot or more below the water surface, causing it to misstate the depth of suspended fish or the bottom.  Objects at the outside of the transducer’s cone appear to be deeper than they actually are.  Depth charts are not always precise, and water level fluctuations can cause them to be off at times.

The Trolling Angles app can run on any fairly recent Android operating system (since Android 4.4, API level 19, released in late 2013), and does not require an internet connection except to show ads and to show documentation.  An older retired smartphone without cell service can be used to run Trolling Angles and other apps like the camera, GPS apps, etc. , and can still connect to the internet over a WIFI connection when one is available.

Always be careful to keep your phone safe and inside the boat in case you drop it.

Yes, it sometimes is. You should become familiar with the quickest way to adjust the screen brightness of your particular phone. In sunlight, you can turn up the brightness and try to keep the phone in shadow, and while measuring angles, know where the Done button is, so you can press it without watching it.

Keep the phone in the shade when possible, to increase visibility, and also to keep the phone from overheating and shutting down on a warm sunny day.

The settings page allows you to select from three different color themes.  The Dark theme might work better in some conditions, especially at night.

The app can display boat speed in either miles per hour (MPH) or in kilometers per hour (KPH).  The length fields and calculations are essentially unit-less, and can be measured and entered in meters, and then depths must interpreted in meters.

No. At this time, the Trolling Angles user interface is English only.  We will provide other languages in the future if the English app is successful.