Introduction to LCCS¶
The Food and Agriculture Organization’s (FAO’s) Land Cover Classification System (LCCS) has two stages, a Dichotomous phase (Level 3) and modular-hierarchical phase (Level 4).
Dichotomous phase (Level 3)¶
The initial stage is a 3-bit binary (i.e. three dichotomous fields) classification scheme, giving 8 (i.e. 2^3) classes.
This is coded progressively as (A|B)[(1[1-4]|2[5-8])], meaning that
a string representation of the Level 1-3 classification has a length of
1-3 characters respectively.
- Level 1: Vegetation (A) or bare (B).
- Level 2: Terrestrial (1) or aquatic (2).
- Level 3: Managed (odd) or natural (even). The value for this
numeral is
1 + managed + 2*aquatic + 4*bare.
Thus, for a complete Level 3 (L3) classification, the 8 allowed codes are A11, A12, A23, A24, B15, B16, B27, B28. Note that the third character fully encodes all three levels; the preceding two characters are redundant.
Modular-hierarchical phase (Level 4)¶
The final stage (Level 4; L4) applies a different classification scheme to each of the eight L3 classes separately. Each class scheme consists of roughly a dozen additional categorical classes (L4 classes). Some of the L4 classes are common among multiple L3 classes (i.e. LifeformVegCatL4a), and other fields are specific to one class (i.e. CropcombAgrCatL4a). In total there are 41 L4 classes. Some fields only have minor differences, for example there are several variants of main life form (i.e. main vegetation) field.
Within each L4 class scheme, there is a superficial organisation among the fields. The fields are grouped (conceptually), ordered (in a sequence relating to intended priority of data acquisition), and categorised (as land cover, environment or discipline-specific).
The L4 classes operate in a hierachy fashion, whereby several classes must be present for subsequent classes to be populated as useful landscape descriptors. All of the L4 classes are categorical (i.e. multiple mutually-incompatible choices), with several having continous input data (i.e. CanopyhtVegCatL4d). For some fields there are possibilities of answering with greater or lesser specificity, or in other words, there is a heirarchical relationship among the possible choices. Usually this relationship is encoded by appending (i.e. concatenating together) certain modifier codes to progressively add specificity. Abstractly, the valid alternatives for a given field can be represented as simple rooted paths of a directed graph structure.
The L4 codes are usually unique within a single L3 category, with some exceptions which must be interpreted in relation to preceding codes. For example, some modifier codes are repeated for multiple parent options (or can be used without any parent code, to convey a different meaning again). Similarly, the same height codes are used for multiple levels of natural vegetation.
The scheme permits only finitely many possible classifications, and LCCS assigns each distinct classification a single unique integer for convenient representation in GIS applications.
The Modular-hierarchical phase has been well documented within the l4_layers_lccs.py code, with docstring for each L4 class describing modifications from FAO LCCS (optmised for EO implementation). All dependencies and permitted additional attributes (i.e. concatenating for useful landscape descriptions) are documented with unit tests performed on each L4 class.