Question on zonal statistics

Discussion created by liana1 on Mar 18, 2013
Latest reply on Mar 19, 2013 by liana1

I am just starting working with GIS and I have two questions. I have a raster file on precipiation and I want to combine it with a shapefile with the boundaries of countries all over the world (e.g. World Bank) in order to get zonal statistics
If  I understand correctly I need to choose the rig ht projection (e.g. Cylindrical, Eckert IV, Eckert VI, Mollweide, Flat Polar Quartic, Sinusoidal) in order to make sure that each cell respresents the same area.
1) Does this indeed resolve the issue? When I tried another projection (GCS_ETRS_1989) I got the same area for all the countries and the same mean for precipitation.

2) While in my original shapefile I have 253 countries, when I do the zonal statistics I am left with 183 coutnries. Any explanation about why this is happening?

Thanks in advance!