Jennifer, yes, they can. Depending on your method of selection criteria you can use an ocean layer to select the areas you want to exclude rather than selecting by elevation.
The accuracy will vary quite a bit depending on the scale, resolution of your data-sets, and how well the data-sets align. If you do select by elevation you can refine your selection a few times to include areas that were left out the first time. Most GIS work takes multiple iterations to get the final product to the point you want it. Save your work often! On Tuesday, August 13, 2013, Jennifer Jones wrote: > Can areas like death valley and the coachella valley around the Salton Sea > in Southern California that are more than a foot below sea level be > counted? > > > On Mon, Aug 12, 2013 at 6:32 PM, Christopher Tracey > <[email protected]<javascript:;> > >wrote: > > > This is pretty much it. One additional important point is that the data > > within the GIS needs to be setup in a map projection that conserves area. > > If this is neglected, you could end up with area measures that are > > extremely off (probably overestimating), especially in the higher > latitudes > > (in most commonly used map projections). Good luck! > > > > - Chris > > > > > > > > > > On Aug 12, 2013, at 9:15 PM, Neahga Leonard > > <[email protected]<javascript:;> > > > > wrote: > > > > > If you have access to ARCGIS software it would be pretty easy to do. > > > Select your area, exclude oceans (-1 and under meters elevation - in my > > > experience setting the measure at 0 winds up excluding a lot of land > > area), > > > and query for area in whatever units you have set up to measure in. > > > > > > The base-maps are available free from many sources (I have some sources > > > collected here: > > > > > > http://writingfornature.wordpress.com/links-to-interesting-blogs/gis-and-mapping-resources/ > > ). > > > > > > If you don't have access to ARCGIS there are good free options, QGIS > and > > > GRASS being two good free examples. QGIS is a bit more user friendly. > > > > > > Good luck, > > > > > > On Monday, August 12, 2013, Abdel Halloway wrote: > > > > > >> Hi ECOLOG, > > >> > > >> I was hoping you could help me. I'm trying to determine the land area > of > > >> the New World and Old World separately within certain latitudinal > > ranges. > > >> Is there some way of determining this? Any information will be > helpful. > > >> Thank you. > > >> > > >> Sincerely, > > >> Abdel Halloway > > > > > > > > > -- > > > Neahga Leonard > > > > > > *There is not just a whole world to explore, there is a whole universe > to > > > explore, perhaps more than one.* > > > http://writingfornature.wordpress.com/ > > > -- Neahga Leonard *There is not just a whole world to explore, there is a whole universe to explore, perhaps more than one.* http://writingfornature.wordpress.com/
