Keyspatial attributes
Finally, key sites and features marked were converted to pictograms for easier
recognition.
Keyspatial attributes
Having selected the 38 cities around the globe and determined the
boundaries of their urban regions, a still more daunting task lay in wait. What is
important in a region? Somehow the most important areas and sites needed to
be identified and mapped. Some are visible on the aerial images, but many are
toosmall and had to be located from published maps, literature, and consulta-
tions with knowledgeable persons. ‘‘Important” here refers to attributes needed
tounderstand the natural systems present, their human uses, and more broadly,
how the region works.
Land cover types
For mostanalyses, the numerous land covers present in the 38 urban
regions worldwide were distilled to 14 major ones, which were mapped -- nine
area-cover types and five linear-cover types. All but one (region boundary) were
visible on the satellite images. Because some linear features are narrow and less
distinct, published maps were occasionally used for clarification in the mapping
process. A few analyses used other subtle or less common cover types which
were not mapped (e.g., railroads, different crop types, different building-density
areas). The 14 major land covers were:
(A) Salt water (sea, coastal bay).
(B) Freshwater (lake, reservoir, river, major stream).
(C) Forest/woodland (forest of tall trees and relatively continuous closed
canopy, woodland of smaller trees and relatively open canopy; in some
climates the two types are intermixed and difficult to separate on aerial
images).
(D) Small-tree farming (especially coffee, tea, and oil palm plantations).
(E) Cropland (cultivated/tilled fields covering at least 75 % of the area, the
non-cultivated portion usually being forest/woodland and/or built area;
includes non-irrigated and irrigated land).
(F) Grassland/pastureland (includes ranchland, paddockland, and grass-
dominated savanna with scattered trees or tree clusters; cropland fields
are much smaller than the relatively distinct pastures/paddocks [rarely
evident in desert/desertified areas] which characterize most pasture-
land).