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<br />00842 <br /> <br />major drawbacks 10 this approach for long,term monitoring of archaeological site degradation is <br />the large expense for collection of Ihe very high,resolution imagery required to delect the line, <br />scale changes; image acquisition costs for just four 100-m-wide archaeological sites was $20,000 <br />due 10 helicopter time required to acquire the high-resolulion images. In addilion, collection of <br />such data requires a very low (240 m AGL) helicopler flight, which may become a noise issue <br />wilhin Ihe park. Even if a larger lens was employed. the flight altitude of 480 m would still <br />require expensive helicoplers and Ihere would still be a noise issue. <br /> <br />We have found photogrammelric elevation data produced from I :4.000-scale <br />photography to yield vertical RMSE values of28 cm (Davis et aI., 2002b) and average elevation <br />errors of 34 cm (at the 95% confidence level) at a cost of aboul $3,000 per river km. Stereo <br />image data at this scale may be oblained annually for the enlire river corridor for only $180 per <br />river km to support other GCMRC monitoring prolocols. A Ithough such data may be acquired <br />for other resource needs, only a small fraclion (22 miles) of the collected data would be <br />photogrammetrically processed and the phologrammetric analysis of the data represents a large <br />fraction of the overall cost of $3,000 per river km. Thus, even this more conventional <br />photogrammetric approach would be very expensive for monitoring the nearly one hundred <br />archaeological sites within the Colorado River ecosystem (CRE). Ifhigh,resolution imagery <br />could be obtained at reasonable cost, then new image data could be compared with previous <br />image data for each area and only those areas with perceptible changes would undergo <br />photogrammetric analysis, Alternatively, automated. digital photogrammetric technology <br />(ISTAR; Table 2) provides 30-45 cm (RSME) vertical accuracy on bare ground, 1.3-m accuracy <br />in dense vegelation, and corridor,wide topography, in addition to orthoreclified imagery, at a cost <br />of $625 per river km, The 1ST AR system collects Ihree panchromatic images simultaneously <br />with different view angles, which allows derivation of elevation using automated soft copy <br />photogrammetric technology. This system also simultaneously collects four color bands that are <br />useful for mapping terrestrial physical and biological resources. We will evaluate Ihal elevalion <br />data during 2003 to determine its accuracy for canopy heighls. If the ISTAR data provide <br />relatively accurate canopy heights, then ISTAR technology may become the remole,sensing <br />protocol for large-area requirements for the physical and biological resource programs and may <br />also provide useful topographic data for geomorphic modeling of archaeological siles at no <br />additional expense. We have found that low- and moderate-resolution L1DAR (Light Detection <br />and Ranging) provides less accurate, less dense elevation dala on bare ground than that provided <br />by photogrammetric data. The density of photogrammetric elevation dala is only limited by the <br />resolulion of the stereo imagery (assuming the data are collected with adequate viewing angles). <br />Our recenl evaluations of very high-resolution L1DAR showed that the data provide an 8-cm <br />vertical accuracy and a 4-5 cm vertical precision on bare ground, which is close to Ihe <br />requirements for monitoring the arroyos and check dams near archaeological sites. Such <br />accuracies cost about $6,200 per river km. but also provide useful data to all GCMRC programs. <br /> <br />-- <br /> <br />2.3 Mapping Campsites and Beaches <br /> <br />The quality of20 main campsites and beaches along the corridor is currently evalualed <br />annually by field surveys that map each site's topography and amount of open space. The field <br />surveys are performed by the tine-grained sedimenl team in the physical resource program. whose <br />primary purpose is to map all storage sites for fine-grained sediment wilhin the CRE. However, il <br />is logistically impossible for ground surveys to obtain an accurate inventory within a given year <br />for Ihe entire eRE. This monitoring is beller accomplished using remote-sensing approaches <br />bccause (I) campsites are generally well exposed and the ralher simple paramelers that the <br />ground surveys record for campsite habitability, (2) remote-sensing data can see most terreSlrial <br />storage sites for sediment, and (3) rather simple image-processing algorilhms can be used to map <br /> <br />9 <br />