Also among recently designed instruments currently being evaluated is a 
slope-measuring device, the Stereo-slope Comparator (fig. 9). The Instrument 
is used with contact prints, It uses two small targets that may be fused stereo- 
scopically into a single target, which is raised or lowered with respect to the 
stereoscopic model by varying the horizontal separation between individual targets 
in much the same way that the fused dot in stereometer-type Instruments is raised 
or lowered. However, the dip is determined by actual physical tilting of the 
target in space. Because of vertical exaggeration inherent in most stereoscopic 
models, the dip determined is an exaggerated dip that must be reduced to true dip. 
It might be added that this photogrammetric instrument is one of the first designed 
primarily to meet specific needs of the geologist, although it may prove applicable 
in other fields of photointerpretation. 
Figure 9. -- The Stereo-slope Comparator, an instrument for determining 
angles of slope in stereoscopic models from paper prints.