Geographic Information Systems Stack Exchange is a question and answer site for cartographers, geographers and GIS professionals. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I work in a fire department and i'm mapping all the fires that occur in my area, creating polygons that represent burnt areas. my problem is that the values are not accurate... for instance, arcgis calculates one of the polygons as 51000 square meters when, in reality, I know that the real area is 60000 square meters. the issue is that the relief is not being considered for the measurement and I need to have the most accurate possible values.

is there any way to calculate an area considering the relief in arcgis 9.3?


share|improve this question
Do you have a DEM? If so, you should be able to calculate surface area within the polygons. However, I don't have the Spatial Analyst extension so I'm not sure if you can calculate it using that. You should be able to use open source software such as GRASS GIS to calculate surface area. Check out the tool. – Fezter Aug 8 '12 at 6:38
The average slope of your area would have to be 32 degrees in order to increase 5.1 HA to 6.0 HA. If this is the case, follow @Fezter's advice. If not, the problem likely lies with the coordinate system being used. You are using an equal-area projection, right? – whuber Aug 8 '12 at 13:30
@fetzer - yes, i've the corresponding DEM, but i can't find a way of making the correct mesure... i never worked with grass, so it's like chinese to me... – Marinheiro Aug 14 '12 at 0:14
@whuber - system coordinates i use: Datum_73_Hayford_Gauss_IPCC Projection: Transverse_Mercator – Marinheiro Aug 14 '12 at 0:21

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Browse other questions tagged or ask your own question.