need help with some dimensions

[CircleFaust]

there is a small lagoon near me . i want to find out the length of the section i've marked. what would it be in meters

i spoke to the council and its this image they sent me. the only other info is that the approx area of the lagoon and beach is 21000 sqm


http://img5.imageshack.us/img5/4664/4b6982f3.jpg

 

[CircleFaust]

when i zoom in with google maps there is no detail (we dont have imagery for this level)

will this matter with google earth, it uses the same images doesnt it?

 

[CircleFaust]

i found the scale out

1:1250