In an excavation, a point B is to be set out at a height ∆H = 1.00 metre below street level (Point A). If the points A and B are widely separated, the height difference between them is determined by line levelling with target distances generally between 30 and 50 metres. Pace out the distances between the instrument and the two staffs; they need to be about the same. 1. Set up the instrument at S1. 2. Set up the staff precisely vertically at point B; read off and record the height (backsight R). 3. Set up the staff at the turning point 1 (ground plate or prominent ground point); read off and record the height (foresight V). 4. Set up the instrument at S2 (the staff remains at the turning point 1). 5. Carefully rotate the staff at the turning point 1 so that it faces the instrument. 6. Read off the backsight and continue. The height difference between A and B is equal to the sum of the backsight and the foresight.
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Survey Photos by Tag or CategoryEarth's Largest Survey Photos Collection
Since 2007, Land Surveyors around the world have shared their best Surveying Photos from the field. Inside this collection you can transport yourself to virtually any location on Earth and see how Land Surveyors work, types of equipment being used and environmental challenges associates with being a land surveyor in that location.
Location Based Chapter Hubs also have photos specific to the locations they represent. You can use our Surveyor Apps for quick sharing of your photos from the field.
Note: Members who have uploaded their photos of surveying to this collection can also move their photos to location based hubs. To see how, follow this tutorial.
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