L10Oct07

L10Oct07 - Traverse Definition A traverse is a series of...

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CIVL1009 Survey (2010-2011 Semester 1) Chapter 5 Traverse 1 Chapter 5 Traverse CIVL1009 Survey (2010-2011 Semester 1) Chapter 5 Traverse 2 Traverse Definition • A traverse is a series of established stations tied together by angle and distance • A traverse is usually a control survey • To locate the detail for the preparation of plans • To locate engineering works • The angles are measured using theodolites or total stations, while the distances can be measured using EDMs CIVL1009 Survey (2010-2011 Semester 1) Chapter 5 Traverse 3 Traverse Types of traverses • Open traverse • Closed traverse Known Data •Positions of A and B Measured Data •Length of traverse sides •Angles between traverse sides CIVL1009 Survey (2010-2011 Semester 1) Chapter 5 Traverse 4 Traverse Open traverse • A series of measured straight lines and angles that do not geometrically close • Lack of geometric closure means that there is no geometric verification possible with respect to the actual positioning of the traverse stations • To provide for field verification, refined measuring technique, e.g. measuring the distances twice, are required Control Station Traverse Station
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Chapter 5 Traverse 5 Traverse Closed traverse • A closed traverse is one that either (i) begins and ends at the same point (known as a loop traverse), or one that (ii) begins and ends at points whose positions have been previously determined • Angles can be closed geometrically, and the position closure can be determined mathematically • For a loop traverse, the loop distances and angles can be obtained by proceeding consecutively around the loop in a clockwise or anticlockwise manner Control Station Traverse Station CIVL1009 Survey (2010-2011 Semester 1) Chapter 5 Traverse 6 Horizontal angle Measurement of horizontal angles • Interior angles • Deflection angles CIVL1009 Survey (2010-2011 Semester 1) Chapter 5 Traverse 7 Horizontal angle Balancing angles • Geometric sum of the interior angles in an n-sided polygon Interior Angles = ( n – 2) x 180 o , where is the number of interior angles • When all the interior angles of a closed traverse are summed, they may or may not be equal to the sum required for geometric closure • Acceptable error of angular closure • Acceptable error = x a , where depends on the precision of instrument and specification of that particular traverse practice CIVL1009 Survey (2010-2011 Semester 1) Chapter 5 Traverse 8 Horizontal angle Balancing angles (cont’d) • Example: When = 5 and = 3” Interior Angles = ( – 2) x 180 o = (5 -2 )x 180 o = 540 o • Acceptable error = x = 5 x 3” < 7” • If the angular error is greater than the acceptable error of angular closure, the fieldwork will have to be repeated • If the angular error is small, the field angles must be adjusted so that their sum equals the correct geometric total • The angles can be balanced by distributing the angular error evenly to each angle, given that all angles were measured with the same precision
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This note was uploaded on 12/01/2010 for the course CIVL 1009 taught by Professor Proftam during the Spring '10 term at HKU.

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L10Oct07 - Traverse Definition A traverse is a series of...

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