Archery Sight Mark will save you time by not having to sight your bow at every distance after making adjustments to your equipment. This app will also provide accurate sight corrections for uphill and downhill shots.
Simply sight your bow at three known distances and record your distance/elevation settings in the app. These three reference marks provide the app with all the calibration data needed to develop a quadratic regression model of sight settings.
A graph of the regression model is displayed to provide a visualization of the shape of your sight settings curve. Ideally, you are looking for a plot having a shallow curve with the vertex centered at the graph origin. A 'J' shaped hook in the graph indicates a skewed model. This is most often caused by parallax errors from choosing a reference distance that is too short, or from reference distances that are spaced too close together.
Suitable distance choices for the calibration references would be the shortest and longest target distance you generally shoot over and a middle distance around half way between these two. Distances outside the calibration range are limited to half the difference between the shortest and longest calibration distance.
Units of measure to use for the distance and elevation are arbitrary. I use metres for distance and millimetres for elevation with my target bow. But yards, feet, ticks, clicks, or whatever will work just as well.
• In most situations, the app will provide accurate sight elevations for all distances within the calibration reference range. Sight elevations for distances extending outside the calibration range are also calculated, but may be less reliable.
• Be aware of parallax effects when setting sight marks at close distances. DO NOT use a calibration reference of, say 10 metres and expect the regression model to be accurate. I have found the ideal calibration reference distances are 20m, 40m, and 70m for bows that can flick arrows faster than 200fps.