Aaftab -
The software package ImageJ should do everything that you need.
http://rsbweb.nih.gov/ij/
This is a Java version of NIH Image. Both are open source and there is a
very active user community with a large set of plug-ins to extend
capabilities/automate processing.
If you choose to go the manual route, consider using mass/weight rather
than counting squares. Develop a regression line of mass v. area by
cutting out squares of known area from identical blank paper. Then
simply cut out the areas of interest from your maps and weigh them. Best
to use photocopies of your maps for this.
-David
On 10/6/10 5:33 PM, Aaftab Jain wrote:
Hello,
I am trying to estimate the area of irregular polygons drawn on graph paper
with a known scale.
I currently have 50 sheets of graph paper (one each for my 50 sites) with hand
drawn maps indicating different substrates, centered on a focal point. The side
of each square in the graph is 5m. I would like to draw concentric circles
around the focal point (15m, 30m, 45m etc) and estimate the area under each
circle/annulus that falls within one polygon (substrate) or the other.
Is there any simple graphing/blueprint software which can take scanned graph
paper with a known scale and generate estimates of area? Could I possibly do
this in Arcview 3.2 without importing any UTM data? Essentially, I would like
to look at a map and say: The area of short grass within the 1st concentric
circle (0-15m) is 400 m sq. and the rest is bare ground, etc.
I understand that my alternate solution is to physically count graph squares
within each polygon and estimate the number of partial squares, but I would
like to be as accurate as possible. Further, making that same estimate
repeatedly would generate a different area each time.
Thanks for your suggestions,
Aaftab Jain
Contract Biologist.
Albuquerque, NM.
****************** aaft...@hotmail.com *******************
