April 4th, 2020

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Explanation and Methodology

Whether a surveyor is measuring the topography of a site or the layout of a building, the general principle is much the same; essentially it is about measuring between points and combining this data to produce a composite drawing. The survey methodology used is to survey each feature by observing each point using the latest computerized theodolites .This is basically done by walking across the site and taking readings by observing every feature required. Each feature type surveyed has a unique feature code that is recorded with the measured data. Attributes such as feature size can also be recorded. Specialist software combines all this data to produce a survey drawing.

In principle, this is carried out by setting-up the instrument over a known reference point (referred to as a "Survey Station", or "Control Station"), and observing each feature with the optical instrument. A network of control stations is established, and these are related to each other by observing between these points. This is referred to as a "traverse". Typically, this will be looped back onto itself, to ensure accuracy. This is referred to as a "closed traverse". Features are then surveyed from these known points. Traditionally this survey process has been a two person operation, where one person held a prism (on a pole/staff) over each feature required to be recorded, and the other person would take a reading to the prism by focusing on it through the optics of the instrument. The height of the instrument on its tripod and the height of the prism on the pole will have been measured in advance and recorded. The instrument records bearing & distance for each surveyed feature. But now as the technology changes so as we. Specialist processing software computes this information and data, and produces a structured computer drawing of the site; which can be viewed on screen in 3D.

True Earth Surveys Pvt. Ltd uses the latest generation of RTK and Scanner Total Stations. As the name implies, these instruments only require one person to operate. The surveyor sets up the instrument over the control station, and then carries out the survey work by walking the site with the survey prism & pole. The instrument tracks the prism automatically, and the data recording and coding carried out by the surveyor is communicated by radio link between the instrument and the data logger which is connected to the prism & pole.

The instruments used by True Earth Surveys Pvt. Ltd also have "non-contact" Electronic Distance Measuring (EDM) technology. These are often referred to as "Direct Reflex" or "DR" instruments, and these utilize an advance pulse measurement technique. This enables a surveyor to survey remote features without the need to gain direct access with the prism & pole. A direct observation is taken by observing the object through the instrument.

This non-contact capability is extremely useful for gaining information in hazardous or inaccessible areas; for example, overhead cables, bridge soffits, ridge & eaves heights & overlooking window positions of buildings adjacent to the survey area, or even the position of nearby railway tracks that can be surveyed without the need to enter dangerous areas.