Wednesday, March 11, 2020

FUNDAMENTALS OF SURVEYING : Plans & maps


Plans & maps:
What is the difference between plan and map?
Plan:
> Plan is a graphical representation ofthe feature on or below the surface ofthe earth constructed by using orthographic projections on a horizontal plane without considering the curvature of Earth.
> A plan is drawn relatively to large scale. Map:
> When the scale is small plan is called map. A map is generally drawn when extent of area is large such as city map, district map, country map, etc.
> On a map vertical distances are also represented by contours, hatchers, etc.
> Projection system other than orthographic system is used.
Scale:
> Scale is the fixed ratio that every distance on plan or map corresponds to a distance or ground.
Scale = Distance on plan or map distance on ground
> A good draughtsman can plot to an accuracy of  0.25 mm.

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