Transverse/offset surveyTo survey the field ABCDE:Choose any suitable diagonal, ie ADMeasure the lengths along the transverse line, ie AP, PQ, QR and RD.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:Start at one end of the transverse lineWrite down the cumulative distances of the offsets from the starting pointWrite down the lengths of the offsets.Units are not shown.

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

NoteThe 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

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

NoteOnly 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

Todays 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.a) BOC == 360 68 81 87= 124Just type it in.c) Area = absinC = 19 33 sin124 = 2599m2

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.a) NOE == 53NOG == 360 318= 42GOE == 53 + 42= 95c) Area = absinC = 49 29 sin95 = 7078m2

Todays workExercise 6G pg 197#2a, 3a, 4, 5,

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