Transverse survey E Transverse or offset surveys are used to find the area of irregular A shapes, such as the field ABCDE to the right. In this method the surveyor: •walks along a straight line (eg AD), B C •the transverse line, •often a diagonal of the area to be surveyed, •measuring distances along this line and •distances to major features, or offsets, when they are at RIGHT ANGLES to the transverse line. •For example… D Transverse survey To survey the field ABCDE: 1. Choose any suitable diagonal, ie AD 2. Measure the lengths along the transverse line, ie AP, PQ, QR and RD. 3. Measure the lengths of the offsets, ie BQ, CR and EP. Field diagrams When in the field doing the survey the surveyor sketches the information as a field diagram. To complete a field diagram: 1. Start at one end of the transverse line 2. Write down the cumulative distances of the offsets from the starting point 3. Write down the lengths of the offsets, on the left or right, as appropriate. 4. Units are not shown. 20+27=47 Example 1 a) Complete a field diagram for this field J 40 K 28 30 22 15 I L 20 14 H b) Calculate the area of this field. A1 = ½bh A3 = ½ × 28 × 10ATOT = 140+384+140+300 = 140 = 964u2 = ½ × 20 × 14 = 140 A2 = ½(a + b)h A4 = ½ × 40 × 15 = ½ × (20 + 28) × 16 = 300 = 384 Example 2 D 94 Sketch the field represented by this field diagram. 79 39 C D 47 35 B E 29 27 15 39 A C You may also be asked to: 32 1. Make a scale drawing of the field 35 B 2. Find lengths such as AB 29 20 E or BC. 27 A Today’s work Field Diagrams Worksheet #1, 2, 3, 4 Field Diagram Task On the oval there are two‘irregular fields’ marked with different coloured cones. Use the trundle wheels/tape measures and set squares to measure the offsets for the two irregular fields. Create a notebook entry for the two irregular fields. Sketch the two fields, showing all the appropriate measurements. Calculate the area & perimeter of both fields.