The size of individual elements
An areal element is 400m2 with minimum dimensions of 5 x 80m or 20 x 20m. If the element is smaller than 5m. it is recorded as a linear element with a minimum length of 30m. Elements that do not pass the criteria for either areal or linear elements can be mapped and recorded as point elements or as proportions of a larger element. If an area is less than 400m2 in the survey square but belongs to a larger element outside, it should be mapped as an area. Areal elements are drawn on a separate map from the linear elements.
Assigning Alpha codes
Elements are assigned alpha codes as identification codes that are the same on the map and on the corresponding recording sheet. Capital letters of the Latin alphabet are used for the alpha code. “I”, “O” and “X” and should not be used. Once all the letters of the alphabet have been used then double codes are used: e.g. AA, AB, AC etc. The alpha code for an areal element should be placed as closely as possible to the centre of the element, as shown in the worked examples.
Separate mapping elements that have identical data coding have the same alpha code, but they should be recorded as A1, A2, etc on the map.
Rules for separating map elements (i.e. new Alpha codes)
A new areal or linear element will be mapped and separated from adjacent or surrounding elements if any one of the following nine rules is true:
- A change in GHC.
- A change of more than 30% of a cover of a GHC.
- A change in environmental qualifier.
- A change in site or global qualifier.
- A change in the occurrence of point elements.
- A change in management qualifier e.g. a fence line or age of forest trees.
- A change of at least 30% in the cover of an individual species over the whole element
- A change of at least 30% in any of the TRS layers, if they are being recorded under forest canopies.
- A change in any other specified European habitat, especially the habitats of Annex I of the Habitats Directive.
- A change in the proportion in the Annex I habitats.
In agricultural land separate fields should be mapped individual, even though the boundaries may or may not not be delimited by fence lines or grass strips. These data are required for subsequent spatial analyses.