Definition
An alidade is a sighting device used for measuring angles, typically in surveying or navigation. It consists of a straight edge with a sighting mechanism, such as a telescope or open sights. Think of it as a sophisticated ruler with aiming capabilities. It's used to determine the direction to a distant object or to measure the angle between two objects. Alidades are commonly used with maps or charts to plot positions or bearings. They are essential tools for accurate measurements in the field. Now, GPS has largely taken over.