length

In many ways, research on linear measurement has not answered fundamental questions that were asked 2 decades ago (p 893). Research suggests that students construct meaningful understanding of length measurement as they abstract and reflect on the process of iterating unit lengths (p 895). In contrast to the Piagetian view, a simpler explanation of the mechanism for length conservation is possible.

[or distance]. . . . The most important aspect of linear features is that they have length. The key equation in the spatial analysis of line data is therefore Pythagoras's theorem for finding the length of the long side of a right-angled triangle (p. 142/ see source for more, much more).