I take a lot of soil samples on a half acre grid. Since linear measurements are easier to visualize, a lot of people ask me how far apart those samples are. This is also helpful if you’re trying to make your own sampling map.
An acre equals 43560 square feet. If you want to take half acre grid samples, then each sample represents 43560*1/2 square feet, or 21780 square feet.
If you’re taking samples on a grid, then you can take the square root to find the linear distance between points: sqrt(21780 sq ft) = 147.58 ft
And there’s your answer– points are roughly 150 feet apart!
This also works for 2.5 acre grids where one sample represents 108900 square feet and samples are sqrt(108900 sq ft)=330 feet apart– roughly the length of a football field!
Spatially Challenged 