The measurement tool is good for measuring small distances. For precise measurements on larger dimensions it is required to zoom / pan between the end points which is currently not possible.
A simple and flexible solution would be to have a second coordinate system with offset, which can be defined by placing the cursor to a point and zero it (ctrl z).. This way the the cursor could be shown as absolute and relative coordinates to this point. Additionally showing the distance in polar coordinates (distance / angle) would solve this problem and simplifies multiple measurements relative to this point.