Written by Jeff Thurston. Friday, 11 September 2009
Absolutely. Photogrammetry is more important today than it has been at any other time. Many of the current images people see in 3D city models, land use planning, environmental and applications involving the determination of landscape change are directly dependent upon photogrammetric products and services. Photogrammety sits at the forefront of many 3D applications because it can provide digital data immediately, and processing tools for that information are also innovative. Lastly, photogrammetry provides one of the few qualitative approaches for geospatial information available through standardisation of testing procedures and specifications.
Photogrammetry has come a long way since it’s earliest beginnings. That growth has been exponential and the developments have often revolutionary — new optics, innovative algorithms, higher speed, higher quality images, for example. Many people outside of the geospatial may not be aware of the size of the photogrammetry sector and the number of people employed in it. The International Society of Photogrammetry and Remote Sensing (ISPRS) is the largest organisation that represents these individuals and organisations. It supports this work around the world in a variety of ways including, education, research, conferences and publications.
My first involvement with photogrammetry began when I studied forestry in northern Canada. It was there that I learned about stereoscopy, calculating basic stereo photo geometry and became initiated into the process of air photo interpretation. That was not an easy task for a new forester because one had to know how specific tree species grew (which made for interesting learning at the same time). But it drove home the point that photogrammetry was not solely about the images, but also about the interpretation of those images. And that has not changed over time, although today’s digital processing of images is more automated. Yet, when one talks to well experienced photogrammetricists today, they continue to mention the interpretive elements of the process.
We see photogrammetry used in feature extraction applications today. Boundaries can be identified and vectorised, thereby making them available for use in geographic information systems (GIS). While GIS can import airborne images as rasters, these images reach their greatest ‘value’ through digitisation. Why? Because lines, points and arcs are spatially significant for spatial analysis within a GIS and can be used with spatial operators to determine relationships to other data. That is not to say that rasters cannot be analysed spatially, since, they too , are geo-referenced pixel-by-pixel. This is exhibited through GIS software such as IDRISI.
Upon first arriving in Germany I wrote an article about the development of triangulated irregular networks (TIN). The idea behind the article was to construct a history of the development of digital terrain model (DTM). Not long afterward, I received a pleasant note informing me about the powers of photogrammetric derived terrain models. The note was signed by Dr. Fritz Ackermann of the Institute of Photogrammetry at Stuttgart University. He kindly pointed out how the process worked and why it was important to understand. Later we ended up publishing an article he presented. Ackermann became the Founder of INPHO — which was recently merged into Trimble.
The integration of photogrammetric derived images with laser based measurements is a growing field today. In principle, the idea is to develop high resolution digital elevation models (DEM) that show 3D building models together with the detailed textures.
Additionally, the derivation of building and other heights from photogrametry is related to the flight geometry of the aircraft. Geospatially this has important implications where inertial guidance systems, often based on GPS, are used to ensure that aircraft fly level and straight. Thus we see a combination of geospatial technologies that must work together to enable the process of aerial photography to take place. The cameras used in these processes must also then be standardised and specifications made available.
The entire field of photogrammetry consists of several camera manufacturers. They come together using similar test locations and procedures that enable the global community to understand, gauge and interpret various aerial products in a standardised way. EuroSDR is one organisation involved in developing these procedures and processes. This year, one of the winners of the Carl Pulfrich Award, Michael Cramer of University Stuttgart is highly noted for his work in this area.
The quality aspect of photogrammetry work is important. Attending most events that include discussion around photogrammetry will invariably lead to a discussion about data quality issues and hardware specifications. At all times photogrammetrists are interested in the performance of equipment and ensuring that the data produced from it are quantifiable and repeatable. This has importance to the international geospatial community. In on sense it not only builds trust between manufacturers and users based on understanding, but it also sets in motion the procedures for reaching international standards and processing approaches from disparate locations, resources and different applications. This helps to build capacity and smooth the growth toward greater use of these technologies and applications.
Photogrammetry applications excel at providing accuracy down to the range of centimeters. This places these devices in close agreement with GPS reference networks, meaning that the applications can be coupled together over wider regions.
But it would be incorrect to assume that photogrammetry only pertains to the cameras themselves. It includes all of the equipment and processes connected to the production of airborne data and derived data products. This includes stereoplotters, image serving and image processing etc.
Photogrammetry is growing in importance and use. New developments across the work flows incorporating photogrammetry are continually expanding opportunities for building applications using this information. There are specific distinctions between between satellite based imagery and photogrammetry derived imagery from aircraft and UAV. Higher adapatability, increased resolution, ability to integrate with additional sensors and timeliness are just a few of the advantages worth considering.
The role of photogrammetry in the geospatial industry is at the forefront shaping change, innovation and supporting higher demands for understanding planetary change.
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Jeff Thurston is editor, Europe, Middle East and Africa for V1 Magazine and V1 Energy Magazine. He is Co-founder of Vector1 Media.
The Basics of Photogrammetry
Remote Sensing and Photogrammetry Society
Institute of Geodesy and Photogrammetry ETH
Learning Digital Photogrammetry
What is Digital Photogrammetry
Importance of Digital Photogrammetry for a Complete GIS
Integrating Digital Photogrammetry and Terrestrial Laser Scanning
EuroSDR — Photogrammetry Related Researchhttp
Photogrammetric Data Capture and the Creation of 3D City Models