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What Is Horizontal And Slope Distances In Surveying

A total station is an angle measuring device, also known as a theodolite, integrated with an electronic distance measurement unit. Today, total stations have a wide variety of capabilities and are extensively exploited in cadastral surveying, civil engineering and on construction sites. Read on for a synopsis of features, status and trends.

These devices, also called electronic Tachometers, can automatically measure horizontal and vertical angles as well as slope distances from a single set up. From these data they can instantaneously compute horizontal and vertical distance components, elevations, and coordinates, and display the results on LCD. They can also store the data, either on board or in external data collectors. If the coordinates of the occupied station and a reference azimuth are input to the system, the coordinates of the sighted point are immediately obtained.

This information can be directly stored in an automatic data collector, there by eliminating manual recording. These instruments are of tremendous value in all types of surveying. Total Stations offer many advantages for almost all types of surveying. They are used for topographic, Hydrographic, cadastral, project and construction surveys. In this article you can find an overview of the histroy of theodolites and the the latest developments. Surveying skills are usually taught in engineering departments as a field-based class.

Regardless of the equipment, all surveying requires knowledge of the basic fundamentals of topographic surveying. If it is equipped with sensors which measure atmospheric temperatures and pressures the processor can calculate corrections to the initial measurements. The data collected is stored in an inbuilt electronic notebook which usually has sufficient capacity to store the data points collected during an entire working day. Once uploaded to a processing computer or server, the data can deleted from the notebook so it is ready for re-use. However, losing data after a productive day is not only frustrating, but also and above all a waste of time and hence money. It is therefore advantageous when the data stored in the notebook can be regularly exported to external data storage media such as a USB flash drive or an SD memory card.

Integrated with an electronic distance meter to read slope distances from the instrument to a particular spatial entity. Some models include internal electronic data storage to record surveyed points (x—northing, y—easting, and z—elevation), distance and horizontal and vertical angles. The data can be downloaded from the total station to a computer. The application software is used to process results and generate maps of the surveyed area.

A total station is an electronic theodolite and an electronic distance meter . With that information you can use the equations that you studied in chapter 12 of the EA3 TRAMAN to reduce the slope distance. As applied to chaining or transit-tape operations, the calculations are simple; however, as applied to EDM operations, the procedures are frequently a little more complicated, as you will see below. The methods of slope reduction that we will discuss in this chapter should be used only for slope distances that are less than 2 miles in length or for observed vertical angles that are less than 5 degrees.

To measure the horizontal distance between two points, one surveyor uses an EDM instrument to shoot an energy wave toward a reflector held by the second surveyor. Instruments called total stations (Figure 5.14) combine electronic distance measurement and the angle measuring capabilities of theodolites in one unit. Horizontal angular measurements are made between survey lines to determine the angle between the lines. A horizontal angle is the difference between two measured directions. When the vertical angle is applied to the slope distance, the horizontal and vertical distances may be calculated.

Because the instrument combines both angle and distance measurement in the same unit, it is known as an integrated total station which can measure horizontal and vertical angles as well as slope distances. This instrument is provided with an inbuilt microprocessor. The microprocessor averages multiple observations. The processor is capable of applying temperature and pressure corrections to the measurements, if atmospheric temperature and pressures are supplied. By convention, then, land area is measured on a two-dimensional common surface plane projected onto the ground.

So even in hilly terrain, the acre is measured as if the hill were cut off at the horizontal, parallel to the horizon. In practice, this means that property boundary lines are not measured as the true ground distance between two points on the ground, be they iron rods, stone bounds, or rock piles. Instead, boundary lines are typically measured as the horizontal distance between those two points.

The Topcon GTS-2 is a semi-electronic tacheometer that measures slope distances by electronic distance measurement . Since the vertical circle of the GTS-2 had to be read optically, the GTS-2 instrument was unable to display horizontal distances and height differences. Instruments called total stations combine electronic distance measurement and the angle measuring capabilities of theodolites in one unit. Next, we consider how these instruments are used to measure horizontal positions in relation to established control networks. Since the 1980s, electronic distance measurement devices have allowed surveyors to measure distances more accurately and more efficiently than they can with tapes.

The EDM records the elapsed time between the wave's emission and its return from the reflector. It then calculates distance as a function of the elapsed time. Typical short-range EDMs can be used to measure distances as great as 5 kilometers at accuracies up to one part in 20,000, twice as accurate as taping. As you have learned, measuring lines can be ropes, bands, tapes or surveyor's chains.

When you measure long distances, the way you use the measuring line will depend on the slope of the terrain. When the terrain is flat or nearly flat (that is, with a slope of 5 percent or less - see Section 4.0), you can measure the horizontal distances by following the ground surface. This method is usually used in measuring fish culture sites, where steeper slopes must be avoided.

The above figure shows the relationship between horizontal distance and slope distance. The slope distance is always greater than the horizontal distance, which means, greater the slope greater the difference between horizontal and slope distance. If great precision is not required in a few cases and the slopes are not steep, you may use a measuring tape to measure the slope distances. It is practically more comfortable to lay the measuring tape on the ground than use a plumb bob to measure distances. Table 1 shows the effect of using slope distances for various slopes.

These total stations can read and record horizontal and vertical angles, together with slope distances. When target is sighted, horizontal and vertical angles as well as sloping distances are measured and by pressing appropriate keys they are recorded along with point number. Heights of instrument and targets can be keyed in after measuring them with tapes.

Then processor computes various information about the point and displays on screen. Electronic display unit is capable of displaying various values when respective keys are pressed. Using the vertical angle, the total station can calculate the horizontal and vertical distance components of the measured slope distance. This eliminates the need for an assistant staff member as the operator holds the reflector and controls the total station from the observed point. The remote positioning unit, which is attached to a prism pole, has a built-in telemetry link for communication with the total station. Even a person is not needed near the total station.

The Total station automatically moves and locates the target. A person is required at the target at different survey locations. The Robotic Total stations speed up the survey work and reduce the manpower. Robotic total station is the latest, most advanced system on the market today that boasts a new modern design, faster motors, 2000 meter reflectorless range. Available in 1, 3, and 5 second angle accuracies, you can select the instrument that best fits your requirements. In surveying, the advanced electronic instrument used to measure horizontal and vertical angles along with distance is called total station.

Over time, and keeping pace with the microelectronics revolution, the primal design of the total station has been extended with features which have made surveying faster and more convenient. Servomotors enable horizontal and vertical angle movements, thus saving time when staking out coordinates as the telescope aims itself and the surveyor just needs to put the prism in the relevant position. The prism is pinpointed through either radio signals or imaging. Whatever the shape of a parcel-or the topography of the land it contains – surveyors calculate its acreage based on a two-dimensional standard surface plan projected onto the ground.

In most boundary surveys, for parcels less than a few hundred square miles, it is considered a horizontal plane. Even in hilly terrain, the acreage is calculated as if the hills were cut off at the horizontal, parallel to the horizon. Actual surface areas exceed map acres according to the steepness of the terrain. Table 2 shows the degree to which surface acres exceed map acres according to the slope gradient. To measure distances, land surveyors once used 100-foot long metal tapes that are graduated in hundredths of a foot.

Skilled surveyors can achieve accuracies of up to one part in 10,000 . The total station instrument is mounted on a tripod and is levelled by operating levelling screws. Within a small range instrument is capable of adjusting itself to the level position. Then vertical and horizontal reference directions are indexed using onboard keys. It is possible to set required units for distance, temperature and pressure .

Surveyor can select measurement mode like fine, coarse, single or repeated. Total stationis asurveyingequipment combination ofElectromagnetic Distance Measuring Instrumentand electronic theodolite. It is also integrated with microprocessor, electronic data collector and storage system. The instrument can be used to measure horizontal and vertical angles as well as sloping distance of object to the instrument. The measurement results can be recorded into the internal memory and transferred to a personal computer interface.

What Is Horizontal Distance In Surveying Generally a total station measures a slope distance and the microprocessor uses the vertical angle recorded by the theodolite along the line of sight to calculate the horizontal distance. A past land development design plan either for your individual property or for your entire neighborhood would also contain the information necessary to calculate land slopes. An existing conditions plan is a plan that you or a previous property owner might have had prepared for your site by a land surveyor. You could measure horizontal distances and read elevations off of contours to obtain the numbers required to calculate the slope between two points. For many decades, and up until the 1960s, theodolites were the major surveying instruments for collecting geodata referenced in an Earth-fixed coordinate system.

Theodolites measure angles, and the computation of coordinates also requires distances which in the past were measured with chains or measuring tapes. The way I deal with this is to generate a profile of the slope using a line of a known length that is segmentized at a known distance. This way, I can calculate a percent slope for representative distances on the profile, convert slope to degrees, and use trigonometry to determine the horizontal distance. I then use the calculated horizontal distances and with the bearing measurements to generate an approximated location of the critical area that more closely resembles real-world conditions. Indeed, the highest mountain on Earth – Mount Everest with a height of 8,848m above sea level – is named after a land surveyor. George Everest was surveyor-general of India from 1830 to 1843.

Figure 2 shows a modern surveyor in India in action using a total station to map a rural area which is scheduled for urbanisation. The clisimeter is a simple instrument for measuring horizontal distances, as explained in Section 2.7. It can also be used to measure a slope or a vertical angle, but it can only give a rough estimate of these, accurate to within 10 percent.

The modulation pattern in the returning signal is read and interpreted by the onboard computer in the total station. The distance is determined by emitting and receiving multiple frequencies, and determining the integer number of wavelengths to the target for each frequency. Most total stations use purpose-built glass Porro prism reflectors for the EDM signal, and can measure distances to a few kilometers. Reflectorless total stations can measure distances to any object that is reasonably light in color, to a few hundred meters. A total station is an electronic/optical instrument used in modern surveying. It is also used by archaeologists to record excavations as well as by police, crime scene investigators, private accident Reconstructionists and insurance companies to take measurements of scenes.

The total station is an electronic theodolite integrated with an electronic distance meter , plus internal data storage and/or external data collector. In a chain survey distance measured between two-point should always be a horizontal plane. But sometimes due to slope on-ground measurement taken on the sloping ground, slope correction is required. In surveying, horizontal distances are considered rather than slope distances. Because the horizontal distance between two points does not change even if the ground is disturbed.

If the surveyor uses slope distances, then the distance between objects and places would change every time the gradient changes which would be inappropriate. If you are accustomed to working in a CAD environment such as AutoCAD® Civil 3D®, you may be more acquainted with horizontal distances. Horizontal distances ignore the difference in elevation between the two points. The figure below shows two points A and B and a theodolite or total station T set up on a tripod above a ground point G.

Point A is higher than the instrument and is above the horizontal plane through T, whereas B is lower and below the horizontal plane. At T, the instrument is mounted a vertical distance h above G on its tripod . Although taping and theodolites are used regularly on site - total stations are also used extensively in surveying, civil engineering and construction because they can measure both distances and angles.

It's most general use is found in the compilation of planimetric and topographic maps by field methods alone, by which distances, elevations a... Tachoetry is used to measure the lengths of traverse sides, to check the more accurate taped distances in order to uncover gross errors or mistakes and to determine differences of elevation between points. It's most general use is found in the compilation of planimetric and topographic maps by field methods alone, by which distances, elevations and... Whatever the shape of a parcel – or the topography of the land it contains – surveyors calculate its acreage based on a common surface, using basic geometry . And while it is possible to account for the curvature of the earth in land surveying, most boundary surveys for parcels less than a few hundred square miles use plane surveying.

That is, the portion of the earth being measured is considered a horizontal plane. X-northing, y-easting and z-elevation), distance, horizontal and vertical angles. Data can be downloaded from the total station to a computer. Application software is used to process results and generate maps of the surveyed area. This reference is for calculating the horizontal distance between two geographic points at difference elevations and is based on the mathematical relationship between the sides of a right triangle.

The mathematical horizontal distance formula is often used on maps because it does not factor in things like peaks, hills and valleys between the two points. The equipment used with this method includes a highly technical sighting device called a telescope. To use it, you must sight through two crossed hairs; there are also two extra horizontal hairs called stadia hairs. Most surveyor's levels (see Section 5.8) have these stadia hairs at an equal distance above and below the horizontal cross-hair. Theodolites are precision instruments used for measuring angles, electronic theodolites read and display angles automatically. Optical theodolites need to be read manually.