Sunday, November 15, 2009

How do they survey land?

things have changed a lot fr. the 70's, gps is used a lot. i work as a small forestry contractor and use a simple string box (a box with a roll of fine string, tie one end to a tree and as u walk it measures the length of string) and compass. most of our land is old farm land and measure around 100 acres. so we find a fixed point, say a neighbours boundary pin(placed in the ground by the gov. when land is sold) or centre of a road. then with measurements off a map we can find one side of a property, using the same map we find the direction of the boundary (here it is usually 5 degrees off north-south) so all we have to do is stand on the boundary and align the compasss to the right degree marking sight down the compas and take a point in the distance (10 to 30 feet), say a tree or big rock, one guy will run ahead and when he is aligned with the needle of the compasss he will tie a ribbon. compas guy will run to ribbon and take another sighting, run ahead tie a ribbon, take a sight tie a ribbon we just do that till we get to the end of the property, which we have been measuring with our string box. repeat for the other side, then just join the two lines to make a rectangle. but this is really just a educated guess one step to the left or right will throw off the next sighting and your line will run off on a angle. the best and most expensive way is with a transit or gps.

How do they survey land?
Took a class in surveying while in college (1973).





Its basically like drawing an object (say a rectangle or triangle), but you use a transit and a metal ruler.





The transit is the little telescope that sits on top of a tripod. You use it for measuring the angle from one side to another.





The metal ruler, is like a water hose - it was about 200 feet long and 1/4 of an inch wide. Its metal so when you measure, it will not stretch or shrink.





You then measure from one point, or corner to the next corner.





When you finish, you draw a map and use geometry to check your work. All of the interior angles should add up to 360, if they don't you made an error someplace.





These days, modern equipment uses laser but I have no experience with them.

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