We will employ aerial photographs for this purpose. This means that 1 cm on the aerial photo corresponds to 200 m on the ground. This is not exact, as the airplane taking the photographs cannot keep a perfectly steady altitude. Thus, we have about 14 photos from the first set and 5 from the second to cover the same area. These usually look quite dark, unless the plane caught glare from the sun.
Wetlands can appear quite light, however.
You can distinguish them from fields by their irregular outlines and distance from roads. Aerial photos are shot early in the day so that shadows are accentuated, and forest thus have a rough appearance. Conifer forest will appear somewhat darker. On the 1997 set, deciduous forest is a medium grey, while conifer forest is much darker. Conifer forest can look like water on the 1997 set, too.