Chandler, Jim 
acquire à large-scde. The DCS460 was mourted using a simple scdfold plank with a 60mm diameter hole drill ed for 
the camera lens, positioned on a moving overhead gantry 4.2m above the flume. The DCS460 was equipped with a 
28mm lens © that the foatprint of each frame was 4.1 x 2.8m. The difficult channel shape suggested that Stereo 
coverage should be obtained in the form of discrete stereo-pairs rather than more conventional overlapping strips and 10 
overlapping pairs were sufficient at the chosen photo-scde (1:150). Fifty conventional cortrol targets were placed on 
the flooddain and channel sides and these points were again co-ordinated using theoddite intersedion methods. The 
camera was cdi brated using in-situ self-cdi bration methods (Chandler et al., in presg and DEMs subsequertl y agguired 
(Chandler, e al., 1998). 
In order to quantify the acerracy of the generated DEMs, elevations were compared with those measured dredly using 
a motorized profili ng device (Walli ngford, 1999) along several cross ædions, (Figure 1). This figure suggests that 
correspondence is excelent, confirmed by summation of all discrepancies, which reved that a r.m.s.e. accuracy of 
—1.9mm was adiieved. 
3.3 Loughborough Flume 
The work on the large Flood Channel Fadlity (FCF) was replicated at one-quarter scde on a smaller flume based at 
Loughborough University, allowing geder variation of those fluvial parameters that influence process One particular 
variable studied has been the impad of different depths of inundation (height above floodgain), with bedforms 
measured following each experiment (Figure 2). The importance of this work to the photogrammetric community is that 
the whole process has become aroutine operation, completed in less than five hours. This includes image aquisition 
  
   
g1_1, height above floodplain: -0.004m g1. 3, height above floodplain: 0.014m 
   
g1. 5, height above floodplain: 0.025m g1. 7, height above floodplain: 0.040m 
Scale 
z-— Meters 
- 
o 
- 
Figure 2, Flume bed surfaces derived by digital photogrammetry, Loughborough flume 
  
  
  
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000. 253 
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