301-pp11

# 301-pp11 - UNIVERSITY OF SOUTH ALABAMA Once upon a time The...

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1 GY 301: Geomorphology GY 301: Geomorphology Lecture 10: Total Station Surveying UNIVERSITY OF SOUTH ALABAMA Once upon a time…. . The Alidade and Plane Table Surveying ht p:/ www.hugha.co.uk/Tanzania/TanReporter52_files/LR006.jpg An early model alidade ht p:/ www.harborfreight.com/cpi/photos/96600-96699/96669.gif Measurements with the Alidade and Stadia Rod • Stadia Rod: usually a 10 foot rod with feet and 0.1 foot divisions painted on the rod Geometry of Alidade Measurements • Stadia intercept: distance on rod from lower to upper horizontal stadia line; distance ratio is 1:100 9 10 8 vertical cross hair horizontal cross hair quarter interval cross hair ALIDADE STADIA CROSS HAIR ful stadia intercept half stadia intercept quarter stadia intercept stadia rod stadia intercept = 9.9 - 7.5 = 2.4 feet distance = 2.4 x 100 = 240 feet ht p:/ nationalatlas.gov/articles/government/IMAGES/usgs_topographer.gif Ray Measurement Geometry Measurements from the alidade station to a data point are termed rays The ray is drawn on the plane table to track distance and direction, and the elevation of the ray endpoint is calculated in field notes A correction must be made for the difference between the alidade cross hair (CH) intercept and the instrument height (IH) of the alidade (see below): IH=3.5ft Cross hair (CH) = 5.7ft Elevation=161ft Elevation @ Rod = 161ft + (IH-CH) = 161ft + (3.5ft-5.7ft) = 161ft – 2.2ft = 158.8ft 5.7ft

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