Orthorectified photomaps: Photomaps are based on aerial or satellite photos, usually at a large scale (1:5000 or more). Additional features of interest (social boundaries, land use areas) can be added by drawing on transparencies laid over the photos. Rectification is “The process of correcting the geometry of an image so that it appears as though each pixel were acquired from directly overhead. Orthorectification uses elevation data to correct terrain distortion in aerial or satellite imagery” (ESRI GIS dictionary, http://support.esri.com/index.cfm?fa=knowledgebase.gisDictionary.gateway ). Photomaps can be used in participatory mapping, and orthorectified photomaps can be added to a GIS for additional analysis or for planning purposes. An application is discussed in Mather (2000). [FH]

Overextension and underextension of categories in cognitive development refers to extending names to members outside a particular domain, or not extending names to members inside a particular domain. [GEW]