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Laser rangefinder is an instrument that USES laser to accurately measure the distance
Laser rangefinder in the operation of the policy shot a very fine laser beam, by the photoelectric element to receive the policy reflected laser beam, the timer measured the time from the laser beam to receive, calculate the distance from the observer to the policy if the laser is continuously launched, the measuring distance can reach about 40 kilometers, and can work day and night. If the laser pulse is launched, the general must precision is low, but for distance measurement, can reach the good relative accuracy laser rangefinder light weight, small volume, short operation is fast and accurate, its error is only one 5 of other optical rangefinder to several per cent, have been widely used in topographic survey, field measurement, tanks, planes, ships and artillery range of policy, measure the clouds, the height of the aircraft, missiles and satellites, etc. It is an important technical device for the precision of high moving tanks, aircraft, ships and artillery. As the price of laser rangefinders continues to drop, the industry is gradually using laser rangefinders.
At home and abroad, a number of new micro rangefinder with the advantages of fast ranging, small volume and reliable function, which can be widely used in industrial measurement and control, mines, ports and other fields. What is the principle of infrared ranging or laser ranging? The principle of ranging can be reduced to measuring the time required by the light reciprocation policy, and then calculate the distance D through the light speed c=299792458m/s and atmospheric refraction coefficient n. Because it is difficult to measure time directly, the phase of continuous wave is usually measured, which is called phase measuring rangefinder.Of course, there is also a pulse rangefinder, the typical WILD di-3000 needs to pay attention to, measuring the phase is not to measure the infrared maybe laser phase, but measure the modulation in the infrared maybe laser above the signal phase. Construction work is a kind of hand-held laser range finder, is used for house, the operational principle of the same plane object to be tested is necessary and total reflection prism light vertical yao general precision ranging demand collaboration, and house measurement range finder, directly reflect on the metope of smooth measurement, first because the distance closer, reflected light signal strength is enough big.And this can know, is bound to the vertical, otherwise the return signal is too small will not be able to get the accurate distance if plane object to be tested as diffuse can also can generally, in the practical engineering can choose thin plastic sheet as a reflective surface to deal with diffuse severe problem. Ultrasonic ranging accuracy is lower, now rarely used.
This is the use of laser monochromaticity and coherence, strong directionality and other characteristics, in order to end high-precision measurement and detection, such as measuring length, distance, speed, Angle and so on.Laser ranging can be divided into pulse laser ranging and continuous wave phase laser ranging.Pulsed laser ranging principle similar to radar ranging, rangefinder emission laser signal to the policy, policy will be reflected back, because the speed of light is known, so just recorded optical signal under reciprocating time, with the speed of light (300000 km/s) multiplied by the reciprocating one half of time, is to measure the distance.Hand-held and portable rangefinders, now widely used, range from hundreds of metres to tens of kilometres and measure with a precision of about five metres.
Application of hand-held laser rangefinder in archaeological research
At present, the country archaeology widely USES the tape measure, the steel tape measure, the GPS, the total station instrument and so on to carry on the length, the area, the volume and so on quantity calculation, USES the total station instrument, the gps-rtk and so on to carry on the topographic mapping, the exploration layout, the project lotting.So what can hand-held laser rangefinders do?The handheld laser rangefinder can also be used for measuring distance, area, volume and lofting with the collaborative theodolite.
Distance measurement is the most widely used function in archaeology. The following two examples illustrate: 1. In the process of making the flat and section drawing of the tomb, the length, width and height of the tomb should be measured and registered, and then made according to the scale.It is assumed that the tomb is an earth pit tomb with a vertical hole and the mouth bottom is the same size. Suppose to measure the width of the tomb chamber, set the handheld laser rangefinder to initially calculate from the bottom of the instrument, and then stick the bottom of the handheld laser rangefinder to the tomb wall, stick to the horizontal button, and then the width of the tomb data will flash on the screen.The length measurement is similar to the width. The depth measurement can be directly measured from the tomb entrance, and the policy plate is also placed at the tomb entrance to measure from the bottom of the tomb. It is assumed that in order to avoid the influence of inclined tomb wall, the time delay measurement can be carried out by using extension bar when the bottom of the tomb mouth is different. 2. The measurement of the mound. Set the handheld laser rangefinder to triangulate, and then take the handheld laser rangefinder as the pole (preferably level with the bottom of the mound) and measure the distance to the bottom and top of the mound respectively. Then the height of the mound will be automatically calculated and flashed in the instrument. This function is particularly useful in the wild, in the Great Wall resources query some beacon tower climb up may be difficult to access, can use this function to measure the height of beacon tower;In the third national census of cultural relics, some ancient buildings, stone carvings are also very difficult to get close to, can also use this function measurement.
Area and volume measurements are also widely used in archaeology.For example, exploration area, tomb opening area, city site area, exploration square, tomb earthwork, etc. To use these functions, simply switch the function options of the handheld laser rangefinder to the corresponding options, and then measure two or three data of the entity to get the area and volume data.
Summary and Suggestions
The hand-held laser rangefinder is sensitive, accurate, simple and easy to operate.However, it also has disadvantages, such as: the measuring range is close, generally about 200 meters, can not meet the requirements of large planning measurement;Prices are high, usually ranging from hundreds to thousands of yuan.Therefore, in the archaeology we should use the hand-held laser rangefinder and other surveying and mapping instruments in cooperation, will give full play to the interests of various instruments, traveling archaeological surveying and mapping, mapping accuracy and power.