Classification of Surveying

Surveying may be classified on the basis of nature of the survey field, object of survey, instruments used and the methods employed.

1. Classification Based on Nature of Survey Field

This basis survey may be classified as land survey, marine or hydraulic survey and astronomical survey.

Land Survey

It involves measurement of various objects on land. This type of survey may be further classified as given below:

(a) Topographic Survey:

It is meant for plotting natural features like rivers, lakes, forests and hills as well as man made features like roads, railways, towns, villages and canals.

(b) Cadestal Survey:

 It is for marking the boundaries of municipalities, villages, talukas, districts, states etc. The survey made to mark properties of individuals also come under this category.

(c) City Survey:

 The survey made in connection with the construction of streets, water supply and sewage lines fall under this category.

Marine or Hydrographic Survey

Survey conducted to find depth of water at various points in bodies of water like sea, river and lakes fall under this category. Finding depth of water at specified points is known as sounding.

Astronomical Survey

Observations made to heavenly bodies like sun, stars etc., to locate absolute positions of points on the earth and for the purpose of calculating local time is known as astronomical survey.

2. Classification Based on Object of Survey

On the basis of object of survey the classification can be as engineering survey, military survey, mines survey, geological survey and archeological survey.
(a) Engineering Survey: The objective of this type of survey is to collect data for designing civil engineering projects like roads, railways, irrigation, water supply and sewage disposals. These surveys are further sub-divided into: Reconnaissance Survey for determining feasibility and estimation of the scheme. Preliminary Survey for collecting more information to estimate the cost of the project, and Location Survey to set the work on the ground.

(b) Military Survey: This survey is meant for working out plans of strategic importance.

(c) Mines Survey: This is used for exploring mineral wealth.

(d) Geological Survey: This survey is for finding different strata in the earth’s crust.

(e) Archeological Survey: This survey is for unearthing relics of antiquity.

3.  Classification Based on Instruments Used

Based on the instruments used, surveying may be classified as:

(i) Chain survey
(ii) Compass survey
(iii) Plane table survey
(iv) Theodolite survey
(v) Tacheometric survey
(vi) Modern survey using electronic distance meters and total station
(vii) Photographic and Aerial survey

The survey is taught to civil engineering students mainly based on this classification.

4. Classification Based on Methods Employed

On this basis surveying is classified as triangulation and traversing.

(i) Triangulation: In this method control points are established through a network of triangles.
(ii) Traversing: In this scheme of establishing control points consists of a series of connected points established through linear and angular measurements. If the last line meets the starting point it is called as closed traverse. If it does not meet, it is known as open traverse.

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What is Subcontractor

A subcontractor is a person or a company hired by a general contractor to perform part of the work of a construction job. For example, a contractor might be building a house, but might hire a firm or a person specializing in electrical engineering to install the electrical systems needed in the house. Generally the subcontractor will either relieve the main contractor of part of the building work, or will be able to perform work at lower expense or at a greater skill level than the general contractor could.

Often, a subcontractor, whether an individual or a business, forms relationships with several general contractors. The general contractor working with a subcontractor does not employ the subcontractor as a regular employee in most cases. Instead the subcontractor is either an independent contractor, or is a company that provides its employees with required benefits like health insurance coverage.

Not having to extend benefits to a subcontractor is one way that the general contractor saves money on a job. However, if problems occur because of faulty work on the part of the subcontractor, usually the general contractor is held liable for such problems. The general contractor may attempt to seek redress with the subcontractor, or have defined terms in the contract with a subcontractor stipulating that the liability would be more evenly shared.

Frequently, though, hiring a subcontractor, or several, is a way to avoid problems in construction. Specialized workers like plumbers, electricians, or people who install heating and cooling devices, often called HVAC workers, tend to have more knowledge and training in their given field. While simply building something requires training and knowledge, people who are specialists better perform certain types of work.

The subcontractor and the general contractor are served well by being able to form good working relationships with each other. For the general contractor, access to a reliable subcontractor can mean finishing jobs on time and on budget. For the subcontractor, a good reputation among contractors means greater opportunities for consistent work.

A subcontractor often holds licenses in his or her specialty field. He or she might hold a general license to conduct work in a state, and also hold advanced licensing. Such licensing implies a certain amount of hours practicing his or her trade and knowledge regarding state building codes.

In some cases, one may also refer to a person hired for a few days of work, without a specialized field as a subcontractor. Really the more accurate term is independent contractor. The person is usually a temporary employee of the contractor, hired to finish work on time, or to temporarily replace another worker who is ill. This type of subcontractor may not have a general contractor’s license but may be hired for his or her carpentry skills.

AFATECOL ................. "Engineering your dreams with us"