It is important to mention that the accuracy of the calculations depends on the quality of the picture. For best results you need to take a picture of the object of interest from a short distance. Also, you need to point the camera straight at the object of interest and you should NOT take the picture from an angle. In other words, stand in front of the object. If that is a distant object, position yourself to the shortest possible distance from that object.
Next you add points by merely tapping on the screen. Every time you tap on the screen you add a point. Based on the selected measurement, you might add a point for the yardstick or a point for the calculation. The yardstick point has a blue background, and the calculation point has a yellow background. The number of points that you can add depends on the selected measurement.
If the selected measurement requires to enter the yardstick points, then the first points that you add are the yardstick points.
If you make a mistake you can change the location of a point by dragging it or you can click on the “Redo” button to start over. While you drag a point, the app will compute the calculated property based on the current position of that point.