Who doesn’t love an alidade? We sure do, and not only do we sell a high-quality, military-grade telescopic alidade, we also enjoy spreading some information about alidades and the many tasks they help professionals accomplish every day.
Telescopic alidades have been used by surveyors since the early 19th century. Along with a plane table, these two tools were essential for mapping and surveying tasks. Alidades also are components in theodolites, another must-have surveying tool.
These days, theodolites are more commonly used, as well as total stations, for many surveying tasks. But there are a few people who still will grab a small alidade and a plane table and take these out in the field to survey a parcel of land.
The surveyor will mount the plane table onto a tripod and adjust the table to ensure that it is level. The alidade is then used as a sighting instrument to help make calculations regarding the land topography and these measurements are noted in a log book and on the survey drawing affixed to the plane table.
Fire Safety & Support
Throughout the United States, there are more than 1,000 lookout towers. These towers typically are staffed by individuals (fire lookouts) working for the U.S. Forest Service who spend their days looking for fires in wilderness areas.
In some cases, the towers are tall structures accessed by an abundance of stairs. In other cases, the towers might be placed at the tops of mountains or hills which offer a substantial view of a wide area.
Fire lookout towers tend to be fairly simple structures equipped with just a few tools, such as binoculars, a two-way radio and an alidade. For lookout purposes this alidade is a circular map with a compass mounted on it. This helps identify precisely where a fire has started, and in which direction it might be moving. The proper name for this type of alidade is an Osborne Firefinder, which was named in honor of its inventor W.B. Osborne.
Many of these lookouts are historic structures, and you can learn more about them at http://nhlr.org/, which keeps a listing of every historic lookout in the United States, some of which are even available for rent and you actually can spend the night in an old lookout tower.
Astronomy & Navigation
Alidades have been used by astronomers for centuries to help plot the location of stars. Early versions of alidades were just staffs that included a sighting slot, but alidades also often were part of a device called an astrolabe.
The astrolabe, is a circular device that was used not only to locate the positions of stars and create star maps, it also was used tell time and to help people determine their location. Many of these astrolabes were small and easily hand-held, which meant if you wanted to check your location on a sea voyage or determine what time it was, this handy tool was easy to tote just about anywhere.
It’s likely that famous sea explorers such as Christopher Columbus, Magellan and others had astrolabes with alidades aboard their ships. Today, modern ships come equipped with high-tech GPS and other navigational equipment, but the alidade is still a common fixture, as well. Alidades are used today as components on giant radio telescopes, such as the Arecibo Telescope in Puerto Rico and the Green Bank Telescope in West Virginia, although these alidades obviously no resemblance to the telescopic alidades we produce.
Telescopic marine alidades are mounted on Navy ships and other large seafaring vessels. These devices are used to sight objects in the distance. For instance, a soldier on an aircraft carrier might look through the alidade to identify the location of another large ship. You also could use the alidade to determine your own vessel’s position, using a landmark as a point of reference.
Our WK-13-7500 Telescopic Marine Alidade is a durable piece of equipment meant for navigational use on large ships, such as Navy vessels. Our telescopic alidade includes a reticle-equipped, terrestrial telescope for viewing distance objects and an auxiliary optical system for viewing the compass card and the bubble in the level vial.