The image you just imported into the applet has some indication on its dimensions, but the applet itself does not yet know them. Let’s use the Screen scaling tool
to correct that. When you press this button, a line appears in the input area at the bottom of the applet. Edit the proposed value and set it to the known distance in the figure (10 meters)
. Then press and hold the left mouse button on the first known point (for example the left bullet of the dimension line, and drag the mouse all the way to the other extremity. A light blue line is showing the distance between the two points, as shown in Figure 3, then release the mouse button. The coordinate system has automatically been adjusted to your input.
Figure 3: Screen scaling : the distance between the beginning and the end of the light blue line will be set to precisely 10
to correct that. When you press this button, a line appears in the input area at the bottom of the applet. Edit the proposed value and set it to the known distance in the figure (10 meters)
. Then press and hold the left mouse button on the first known point (for example the left bullet of the dimension line, and drag the mouse all the way to the other extremity. A light blue line is showing the distance between the two points, as shown in Figure 3, then release the mouse button. The coordinate system has automatically been adjusted to your input.