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Construction surveying is the translation of construction plans into physical points on the ground. These physical points can then be used as a basis for the actual construction. The results of construction surveying are seen in almost any urban, suburban, and even rural setting. Almost any roadway, building, or other man-made improvement probably had some amount of construction surveying involved. Construction surveying provides not only the horizontal location of new improvements, but also the vertical information required to ensure that surfaces drain or pipes flow as designed. The stakes and monuments set during this process are not usually set at the actual construction point, but usually an offset of the actual location. This is done so that the survey stake is not disturbed by excavation or other activities that will take place at the actual point of construction. The stakes are marked with an "offset" and a "grade", which provides the construction crew with the spacial relationship of the construction stake to the actual point of construction. The "offset" is the distance from the survey stake to the horizontal position of the actual point of construction, and would typically be at a predetermined distance. The distance of the offset should be coordinated with the contractor to accommodate any specific needs due to existing field conditions or special equipment, and should be clearly marked on the survey stake. The "grade" represents the change in elevation that needs to be obtained from the reference point to the actual construction point, expressed as a "cut" (lower in elevation) or a "fill" (higher in elevation). The grade should also indicate the vertical feature that the grade is referencing, usually a flow line or finished floor elevation. The need for accuracy is inherent in all of the surveyor's tasks, this is especially evident with construction surveying. It is not only important to perform all calculations accurately but also to communicate clearly with the contractor the distance of offsets and reference points for grades. For example, if the surveyor provides grades to the flow line of curb and gutter and the contractor uses those grades as top of curb elevation, the net result is a construction site that is not going to work as designed. Scheduling of Construction Staking should be coordinated in a manner that minimizes the risk of the stakes being damaged by human or natural activities, as any disturbance to the survey stake may carry over to actual construction. |
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