Culture and Ecology of Chaco Canyon and the San Juan Basin

The NPS Chaco Project 9Figure 1.4. 1929 oblique aerial photograph of Chetro Ketl. (Photograph from the Carlos Vierracollection, Museum of New Mexico.)Aeriol Photography. Aerial photography isstill the most useful and cost-effective type of remotesensing; variables such as the platform chosen, type offilm used, and time of day affect its utility. The sizeof an area and the amount of detail desired conditionthe choice of platform. Experiments with a BipodCamera Support System, which raises the camera9.14 m (30 ft) above ground (Whittlesey 1966) proveduseful in documenting and analyzing different strata inroom excavation (Klausner 1980), but at this heightpreparation of a site map by combining photographsinto a mosaic is not as satisfactory or efficient as useof plane table and alidade (Jacobson 1979). Intermediateplatforms were tested. Kites and balloons areaffected by wind gusts; a tethered balloon is unstablein gusts above 24 km per hour and its optimumelevation is around 400 to 600 m above ground(Camilli and Cordell 1983:76). More recentexperiments with a remote-controlled small airplaneby Jim Walker of Brigham Young University and ArtIreland of the NPS overcame the disadvantages ofkites and balloons and provided coverage of areas atsome distance from the operators. Although thesesmall planes cannot fly in air currents over 19.3 kmph(12 mph), coverage can easily be varied by adjustingthe altitude (optimally between 30.4 to 304 m [100 to1,000 ftn to obtain overviews of an area or closeupviews of specific features (Art Ireland, personalcommunication, 2004; J. Walker 1993). A full-sizedaircraft, however, is the most common platform;altitude can be varied and controlled, and photographscover large areas that can be analyzed for natural andcultural features. If ground control is set beforehand,the photographs can be combined into mosaics toobtain a regional perspective. They can also be usedto produce maps of different types. Table 1.1 lists