Land survey freeware sources?

January 15, 2007 7:55 AM

I am wondering if anyone knows where to find free ware/economical software that will calculate the surface area of an object defined by a closed curve saved either as a bitmap or vector image?

*I am asking this for a friend who is swamped with deadlines*

"I have traced various study areas on a map and I want to be able to
determine their surface area accurately. There are devices to do this but
they are expensive. I though that if I traced them I might be able to find
software that can import these curves and calculate the surface area."


Does anyone have any suggestions they could offer?

posted by plumberonkarst to computers & internet (6 comments total)

I can tell you that the devices apply Green's Theorem. I've forgotten the name, but wikipedia calls it a Planimeter.

I can't help you any further, but you could try a google for "planimeter software", or some such..
posted by Chuckles at 9:12 AM on January 15, 2007

Well, can't help you further except that there are probably some back of the envelope ways of doing it..

You could fill the traced outline with black, the background with white, and then get photoshop (or equivalent) to tell you how many pixels of black you have. Then, dividing by pixels^2/cm^2 (squared because it is area, pixels in the digitized image per cm on the original map) will give you a fair approximation of the area on the map that has been traced. And, dividing by the scale of the map squared will give you the real area, but you will probably have lots more unit conversion to do after that - to acres, or whatever..
posted by Chuckles at 9:24 AM on January 15, 2007

How about printing out the shapes on a printer, cutting them out, and weighing them, then comparing the weights of the shapes with a 1 cm^2 reference shape? All you'd need is access to a good laboratory-grade scale.
posted by ZenMasterThis at 10:13 AM on January 15, 2007

chuckles++
posted by sergeant sandwich at 12:27 PM on January 15, 2007

Import your drawing into Google SketchUp (free), trace it, then right click on the enclosed area and select Area. I know it can give you square feet; you may have to convert to acres or sq. miles or whatever.

(Google proper can do conversions with a query like,

101,623 square feet in acres

to which Google will respond,

101 623 (square feet) = 2.33294307 acres.)
posted by Dave 9 at 2:12 PM on January 15, 2007

Global Mapper's free unregistered version (www.globalmapper.com) may be even easier than SketchUp, depending on the format of the file you want to input. Much easier, if you have a real GIS file.
posted by Dave 9 at 2:23 PM on January 15, 2007