Topographic Surveys

 

G.V. Hull & Associates undertake numerous topographic surveys for local Councils, architects, and developers. Topographic surveying may also be known by CAD operators as Terrain Modelling. The surveyor's aim is to create a plan (or map) of a parcel of land which indicates rises and falls in the level of the land, shows contours which indicate points of equal height, and displays all the major features of the land which may affect the subsequent design stage of the proposed development.

Topographic surveys can be requested by a client to be undertaken over a wide and varied range of property. Urban topo survey sites can vary from flat playing fields to overgrown, scrubby and difficult to penetrate sites. They can be large dusty excavations where the volume of material removed needs to be checked or a small residential building site. Rural and mining topo surveys can be so large that special techniques such as GPS (Global Positioning System) need to be employed.

Topographic surveys in urban areas are usually undertaken using a total station theodolite and data recorder. The surveyor establishes a datum point for his survey and, using a special mirror mounted on an extendable pole, proceeds to make measurements over the site in a regular pattern. Each measurement is downloaded to the data recorder by the theodolite and the point coding information is input by the surveyor.

Back at the office, the data file is transferred to the computer where special software is employed to create a digital terrain model of the survey area. This stage of the survey needs to be as accurate as the actual survey measurements. Incorrect interpretation of the data will result in an erroneous plan and subsequent problems when 'design' comes to 'construct'. A surveyor needs to be constantly watching for any anomaly in the survey as it 'comes to life' on the computer screen. Error detection and tracking is an important part of a surveyors daily routine.

The final stage of plan preparation involves re-checking data strings, ensuring that all relevant information has been included, such as the position of underground services, and putting on the final touches so as to make the plan presentable to the end user.

The 'final plan' is, these days, a bit of a misnomer. Most often we tend to send a floppy disk out in the mail or, as is becoming more and more popular, we attach the plan file to an Email message to be sent out over the Web (together with the invoice generated by the accounting software).

The topographic survey represents an important part of any surveying consultancy and an important design tool employed by numerous engineers, architects and designers.

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