Preliminary legend

Preliminary legend:

Prior to the delineation of the units, a legend is constructed based on Interpretation elements.
The legend can be presented in the form of a table in which each element type is represented by a column ( see the figures below for a preliminary legend and interpretation).

The Table  presents a fictitious example of a legend.  In this legend, the “unit number” represents an as yet unknown feature type; the corresponding row elements will be used to identify that feature type.

When preparing a legend you need to consider that distinguishing units can be based
on a difference in one element only or on differences of several elements. For example,
consider Unit 1 in the Table : its tone is black and all other units have a grey or white
tone. In this case there is no need to define all the other elements for Unit 1. In the example of the interpretation of Manyara , some units are different in texture. There are areas with smooth and rough texture. The rough texture areas are further differentiated according to
height. Furthermore, rough, high areas are differentiated, depending on location in
the mountains or along rivers or near the sea. 

When delineating areas by hand, there is a limit to what can still be drawn. In practice,
polygons smaller than 5 mm × 5 mm should not be drawn. This is called the smallest
allowable unit. The scale of the image(s) used therefore limits the interpretation cell
on the ground. When delineating areas by digitizing on-screen, one could zoom in—
interpretation cell in principle to a monitor dot. However, you need to define the maximum scale at which the given remote sensing data are still reliable and then calculate the smallest
allowable unit.

In some cases an area may consist of two or three different types of too-small areas.
Then, individual polygons for each small area cannot be drawn, even though at a
larger scale the individual features could be mapped. The solution in such a case is to
combine these areas to form a complex unit. The different features of such a complex
complex unit can be described separately. In the table Unit 6 and Unit 7 are two different complex units: in Unit 6 there are two features, namely grey fields and white lines, while in
Unit 7 there are white fields and grey lines.