I must learn how to use one of these! https://store.wndsn.com/collections...cket-quadrant-telemeter-7x7x500q90i30-acrylic A tool for makeshift navigation and rangefinding, the double-sided Wndsn Pocket Quadrant Telemeter enables you to do more than merely guessing distances. Find an object of known size, or distance, or angle and measure with the appropriate scales and utilize the baked-in trigonometry to find the desired value by aligning the provided string across the various scales. The newly used backside features functions derived from ancient astrolabes; a degree and slope quadrant, a shadow square, as well as sine and cosine arcs and an inclinometer scale. By using our string as a plumb line, we introduce three additional ways of sighting, plus we let you perform various trigonometric tricks with a shadow square and a sexagesimal scale, increasing the usefulness of the instrument with the list of applications topping 50 currently. The Quadrant Telemeter lets you measure angular size and compute distance, height or depth of object, altitude, or elevation, it allows computation of sine, cosine, and tangent for a given angle. The best tool is the one you have with you, on you. Wndsn Telemeters are wallet-size distance and altitude nomographs developed in our applied science lab: Wndsn Telemeters combine a thousand years of civil engineering, surveying, navigation, and astronomy in one durable, low tech, high utility instrument that can be brought anywhere, is self-containing, and independent of external, modern technologies. Wndsn Telemeters are naked-eye tools that offer various means of measuring angular size, as well as graphical computers providing functions to process or convert the measured values. Their purpose is to help you navigate using known landmarks or astronomical features, to get a "second opinion" to cross-check values obtained with different means, or in emergency situations when other methods fail or are unavailable. Wndsn Quadrant Telemeters continue to spark and promote interest in contemporary metrological science and ancient navigational history as well as educational astronomy.