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Bench Marks Bench Marks is a point of known elevation . there are three Type of Bench Marks 1-Temporary Bench Mark . 2-Permenent Bench Mark. 3-Orbitrary Bench Mark Report No. 5 • Report Name : • Fly and Differential leveling using (Rise&fall) and (HI) methods • Object : • To find elevation [reduce level (R.L)] for differential point along ground in side the campus of Erbil Technical college. -Close loop survey. Fly and Differential leveling. Checks for Errors . Allowable error (Misclosure); Is the difference • between the known benchmark and computed benchmark misclosure =Known point- measured point =0 = DH •known – DH measure The allowable error is based on an equation: Allowable misclosure=E =C Where: C=constant C=12 for Mountain area C=30 for Ground levelling R= is total distance by Km Correction= E/n n=Number of T.P stations Prepared by: Asst. Prof. Salar K.Hussein Mr. Kamal Y.Abdullah Asst.Lecturer. Dilveen H. Omar Erbil Polytechnic University Technical Engineering College Civil Engineering Department Read less