Laser Scanning and Photogrammetry: 21 st Century Metrology 
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Figure 6 shows a point cloud captured by a Callidus scanner. The points are coloured based on the value of the normal to that point. 
This is an effective method allowing the differentiation of planes and immediate visualization of edges. This scene consists of over 
half a million points collected in just a few minutes; note how the resolution of the scan degrades towards the edge of the scene. 
Figure 6 also shows a rectified photograph from the same project rectified to a plane. Clearly each dataset contributes its own 
specific information. The image provides information on the materials and colour of the object while the scan data shows the 
topography of the scene, (as with all scan data this is more evident when the scan data can be manipulated on a computer). 
6, INTEGRATION 
The value of complementary data with respect to material types and topography is clear from the above example, but what about 
more complex integration of techniques? Integration of airborne LiDAR systems with imagery is becoming a familiar call, 
especially where DEM extraction struggles in urban areas; Toth and Grejner-Brzezinska (2000) suggest integration of airborne 
LiDAR with imagery at three levels. 
• A visual backdrop. 
• Redundancy to LiDAR data acquisition. 
• Providing an attractive price/performance ratio (and an attractive fall back in unexpected situations). 
These suggestions are equally valid for terrestrial applications, where the problems of surface extraction are more pronounced due to 
the amplified discontinuities typically found in a scene. 
Integration should not be limited to image based methods, traditional survey techniques still have a role. How best to integrate 
scanning with current survey techniques stems from a fundamental understanding of the needs of the end user. The typical product 
required from photogrammetry is a line drawing or orthophotograph. The product required from laser scanning, or the most 
appropriate type of application to apply laser scanning to, is currently indistinct. Scanning has been implemented in a number of 
projects, many of them concentrating on visualization. Such models are impressive but are best viewed as a computer displayed 3D 
model. This may not be suitable for a skilled craftsperson attempting to recreate/repair parts of a historic monument. What is the 
ideal product? The end user must answer this and the surveyor must attempt to fulfill the specification with the most appropriate 
techniques available. 
Figure 6: Left, Example scan of a ceiling at Alexandria Palace, UK (courtesy Callidus GmbH/Jenoptik 
and Alexandria Palace), and right, rectified photography (courtesy English Heritage) 
7. CONCLUSIONS AND RECOMMENDATIONS 
This paper has provided a description of some of the laser scanning systems available and has reviewed how accuracy and integrity 
currently fit into laser scanning compared to photogrammetric methods. With this in mind it has outlined the need for the testing of 
scanners and the need for comparable statistics and data sets. The presentation of data has been discussed and compared with line