Photogrammetry- What is it?

Photogrammetry is the Science of determining spatial data from photographs. The traditional application of photogrammetry in the UK has been the production of all Ordnance Survey maps (1:1250-1:50,000 & derived products such as road atlases) using vertical aerial photography.

Key advantages of photogrammetry include:

• Non-contact method of measurement.
• Precision is flexible and commensurate with scale.

Significant developments in the last thirty years include:

• The computerisation of the restitution process (i.e. the transformation of image measurements --> 3D Object Coordinates). This has freed the type of usable photography from most of the geometric constraints enforced by mechanical and optical limitations of early plotting instruments. Now ground based, oblique/vertical aerial and even satellite imagery can be used using analytical photogrammetry. Furthermore, such imagery can be acquired using a wide range of cameras.
• The parallel development of silicon based technologies have provided the foundation of the logical extension to analytical methods, digital photogrammetry. The huge advantage is the potential of automating certain aspects of the measurement process, perhaps best exemplified by the automated extraction of Digital Elevation Models (DEMs) and orthophotographs. (Example: The Black Ven mudslide complex)

More recent developments (2011) include the availability of free and fully automated software, initially by Microsoft (Photosynth) and perhaps more significantly Autodesk (123D catch). Both initiatives allow any user to upload images acquired with any digital camera, and in the case of 123D catch, to produce a full 3-D mesh in minutes. This is achieved without any user involvement, free of charge. Accuracies are reasonable (1:1,000) as demonstrated by recent tests conducted at Loughborough University.

The increasing need to manage that most basic resource, "space", requires electronic representations of existing structures and the earth surface. Photogrammetry can provide that information cheaply, effectively and efficiently.