International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B4, 2012 
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia 
true orthophoto, in which it is hard to recognize what 
buildings we are looking at because in the orthophoto 
we don't see the familiar buildings sides that we see 
everyday when we stand in front of those buildings. 
People have little chances to see the tops of those 
building presented in Figure 1. Because of these 
drawbacks of 2D orthophotos, true 3D images are 
wanted. An ideal true 3D image would be an image 
that has true 3D coordinates for all its pixels and also 
at the same time allows us to look at the objects in the 
scene it covers as we see every day on the ground. 
     
  
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Figure 1. A true orthophoto 
2. TURE 3D IMAGES AND THEIR 
APPLICATIONS 
2.1 True 3D Images 
For the present time, the best true 3D images can be 
made from airborne oblique images. Taking buildings 
on the ground as examples, an airborne oblique image 
looks down at them with an angle comparing with that 
people look up at them with an angle as well on the 
ground. Although these two angles are different, the 
buildings sides presented in the oblique image are very 
recognizable for people. In general, people have little 
problems to recognize objects in an oblique image 
because oblique images show sides of buildings. 
True 3D images can be produced with airborne oblique 
and vertical images, Lidar data for elevation data and 
exterior and interior orientation parameters through our 
proprietary procedures and processes. Figure 2a and 2b 
together shows a true 3D oblique image. Figure 2a is 
an airborne oblique image and Figure 2b shows the 
200 
coordinates associated with the image, with brightness 
representing — elevation. One can see the 
correspondences between all objects in the two images. 
Among all the objects in the images, all building tops 
and sides have their 3D coordinates and all trees have 
their 3D coordinates as well. 
     
    
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image 
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Figure 2a. An airborne oblique 
  
Figure 2b. An image showing the 3D coordinates 
associated with the oblique image in Figure 2a. 
2.2 Examples of Applications 
2.2.1 Rectified True 3D Images 
We can rectify true 3D image just as people rectify 2D 
orthophotos. Rectified true 3D images can be mosaiced 
together as well and used in a GIS as a standard layer. 
With true 3D images available, users can not only read 
and make XY measurements but also read and measure 
Zs. 
2.2.2 3D Measurements 
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