# maths for surveying purposes

• Jul 22nd 2009, 10:24 PM
masiboy
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
• Jul 22nd 2009, 10:33 PM
CaptainBlack
Quote:

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: $18.3$ and $19.9-9.8$ metres

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

CB
• Jul 22nd 2009, 11:15 PM
masiboy
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???
• Jul 23rd 2009, 02:01 PM
aidan
Quote:

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?
• Jul 23rd 2009, 02:22 PM
CaptainBlack
Quote:

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

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

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

CB

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

CB