tripod a surveyor is a device used to support any of a number of survey instruments, such as theodolites, total stations, levels or transits.
Video Tripod (surveying)
History
A modern, sturdy, and portable tripod with three pairs of hinged legs into a triangular metal head was invented and first manufactured for sale by Sir Francis Ronalds in the late 1820s at Croydon. He sold 140 booths in the decade of 1830-40 and his designs soon imitated by others.
Older tripod surveys have slightly different features than the modern ones. For example, on some older tripods, the instrument has its own footplate and does not need to move laterally relative to the tripod head. For this reason, the head of the tripod is not a flat footplate but only a large diameter fitting. The yarn on the outside of the head ties the yarn on the instrument plate. No other mounting screws are used.
Long legs remain also visible on older instruments. The instrument height is adjusted by changing the angle of the foot. The wide leg of the tripod produces a lower instrument while the legs are close to lifting the instrument. It's much less convenient than having variable long legs.
Materials for older tripods are mostly wood and brass, with some steel for high wear items such as legs or feet.
Maps Tripod (surveying)
Usage
Tripod is placed in the required location. Surveyors will press on the foot platform to secure an anchor foot on the ground or to force the foot to low position on uneven and pitted sidewalks. The length of the foot is adjusted to bring the tripod head to a comfortable height and make it approximately aligned.
Once the tripod is positioned and secure, the instrument is placed in the head. The mounting screws are pushed down the instrument to touch the base of the instrument and tightened firmly when the instrument is in the correct position. The flat surface of the tripod head is called the foot plate and is used to support the feet of an adjustable instrument.
Positioning a tripod and instrument just above the mark indicated on the ground or benchmarks requires a complicated technique.
Construction
Many modern tripods are made of aluminum, although wood is still used for feet. The legs are made of aluminum with a steel or steel tip. Screw mounting often brass or brass and plastic. The hollow mounting screws and have two lateral holes to attach the center point to the center of the instrument, for example through an angle or other mark on the ground. Once the instrument is centered within a few centimeters above the mark, the bob is removed and the viewer (using a prism) in the instrument is used to precisely focus it.
The top is usually threaded with a 5/8 "x 11 tread screw thread.The mounting screws are held to the underside of the tripod head by a movable arm.This allows the screws to be moved anywhere inside the opening of the head.The feet attach to the head with screws that can be arranged which is usually kept tight enough to allow the legs to move slightly with resistance.The legs are two parts, with the bottom capable of telescoping to adjust the length of the foot to fit the Aluminum or steel slip joints with the tightening screw located at the bottom of the upper foot to hold the bottom in place and fix the length.Shoulder straps are often affixed to a tripod to allow the ease of carrying equipment over the area to be surveyed.
See also
- Tribrach (instrument)
References
- Raymond Davis, Francis Foote, Joe Kelly, Survey, Theory and Practice , McGraw-Hill Book Company, 1966 LC 64-66263
Source of the article : Wikipedia
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