Transverse/offset surveyTo survey the field ABCDE:1. Choose any suitable diagonal,

ie AD2. 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 diagramsWhen in the field doing the survey the surveyor sketches the information as a field diagram.

To complete a field survey:1. Start at one end of the

transverse line2. Write down the cumulative

distances of the offsets from the starting point

20+27=473. Write down the lengths of the offsets.

4. Units are not shown.

Plane table radial surveyWhen doing a plane table radial survey you normally:•Place a table towards the middle of a field•Mark a point towards the middle of the paper.•From this point draw a line towards each corner of the field•Measure the distance from the point towards the middle of the paper to each corner of the field

Note•The angles at which the lines are drawn are important as this is used in doing an accurate scale drawing,•It is called a radial survey as all lines “radiate” out from the centre.•The point O is often used as the centre point

Example 1The diagram shows the results of a radial survey of a field ABCD

O

A

BC

D

23m 28m

33m19m

87º81º68º

Compass radial surveyA compass radial survey is similar to a plane table survey:•Stand towards the middle of a field,•Take a compass bearing of each corner of the field,•Measure the distance from the point you are standing to each corner of the field

Note•Only very rarely is one of the corners directly north,•Often the angle asked for involves the corners just to the left and right of due north.

Example 2The diagram shows the results of a radial survey of a field EFG

E 053º

F 197º

G 318º

O

35m

29m49m

N

Today’s work

There are two ‘fields’ marked on the oval.

•Create a radial and compass survey/diagram of each of the ‘fields’.

•On ‘field 1’ use radiating lines (and protractors) and the navigational compass.

•On ‘field 2’ use the giant protractor and the iphone.

•Use your surveys to find the area of the ‘fields’.

•Equipment: pencils, rulers, rubbers, paper.

Example 1The diagram shows the results of a radial survey of a field ABCDa) Find the size of BOC.b) Calculate the length of BC.c) Calculate the area of triangle OBC.

O

A

BC

D

23m 28m

33m19m

87º81º68ºa) BOC == 360 68 81 87

= 124ºAbccbab cos2) 222

124cos193321933 222 x

221512 xmx 446

Just type it in.

x

c) Area = ½absinC

= ½ 19 33 sin124

= 259·9m2

Example 2The diagram shows the results of a radial survey of a field EFGa) Find the size of GOE.b) Calculate the length of GE.c) Calculate the area of triangle GOE. E 053º

F 197º

G 318º

O

35m

29m49m

N

a) NOE == 53ºNOG == 360 318

= 42ºGOE == 53 + 42

= 95ºAbccbab cos2) 222

95cos294922949 222 x734892 xmx 159

c) Area = ½absinC = ½ 49 29 sin95 = 707·8m2

Today’s work

Exercise 6G pg 197 #2a, 3a, 4, 5,