I am relatively new to arcmap. At the moment I am trying to perform what seems like a simple task of digitizing lakes from aerial imagery to calculate their surface area. I have been using the arcgis online MDA NaturalVue Satellite Imagery as it has extremely good resolution for many of the sites I want to use. I have to digitize just under 600 lakes from across the entire northern hemisphere so it seems a good base map to use. However, every time I attempt to do this by using polygons the results that come out for the area are nowhere near correct. I have tried adjusting the coordinate systems but I don't seem to be able to get what seem like reasonable results? I must be missing something simple?
Could anybody offer me any advice for calculating lake surface area from one of the arcgis online maps (perhaps the most appropriate basemap to use), and the relative dataframe/coordinate systems that I need to set my polygon shapefiles to etc?
I know this probably sounds simple but for some reason I just cannot get it to work...