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.

The first measurement with the lure just underwater is critical, because it essentially measures the drag and dive force of the lure alone. The next closest measurements are important, where the line curve angles are changing fast. 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.