# Thread: maths for surveying purposes

1. ## maths for surveying purposes

Hi there,

i have attached a PDF showing a shape, of which i have to calculate area.
i dont know where to start from.it would be much appreciated if anyone can help me out.

thanks

2. Originally Posted by masiboy
Hi there,

i have attached a PDF showing a shape, of which i have to calculate area.
i dont know where to start from.it would be much appreciated if anyone can help me out.

thanks
ABEF is a rectangle of known dimensions, so you can calculate its area

CDEG is a rectangle of sideds: $\displaystyle 18.3$ and $\displaystyle 19.9-9.8$ metres

GBC is a sector of a circle so its area is $\displaystyle \pi r^2 (\theta/360)$, where $\displaystyle r=19.9-9.8$, and $\displaystyle \theta$ is $\displaystyle 82^{\circ}13'46''$ expressed in decimal degrees.

CB

3. thanks Captain Black,now it loks quite straight forward to me, so this means height of 32.4 doesnt play any part in calculating the area???

4. Originally Posted by masiboy
...
i have attached a PDF showing a shape, of which i have to calculate area.
...

Given:
BE and CD are parallel
&
FD and GC are parallel

That implies that point G CANNOT be on the line BE.
If G were on the line BE then angle BGC (which is given as 82deg13min46sec) should equal angle GCD (which is indicated as 90degrees).

It really looks as if this is a "flawed" question.
That is, you are given invalid information for the purpose of understanding how you handle errors.
What data will you use and what information will you ignore?

5. Originally Posted by CaptainBlack
ABEF is a rectangle of known dimensions, so you can calculate its area

CDEG is a rectangle of sideds: $\displaystyle 18.3$ and $\displaystyle 19.9-9.8$ metres

GBC is a sector of a circle so its area is $\displaystyle \pi r^2 (\theta/360)$, where $\displaystyle r=19.9-9.8$, and $\displaystyle \theta$ is $\displaystyle 82^{\circ}13'46''$ expressed in decimal degrees.

CB

Except what I thought were rectangles are in fact not rectangles!

CB