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Can High Resolution Satellite Imagery (HRSI) replace Aerial Photography?

Jul 2008 | No Comment

Can High Resolution Satellite Imagery replace Aerial

Photography?

The answer is yes and no at this moment.

Why no?

Small and medium scale maps 1:50,000 up to 1:10,000 (possibly 1:5,000 in near future) at most can be replaced by High Resolution Satellite Imagery (HRSI), though we need ground survey of many objects which cannot interpreted from the HRSI. I agree that the cost performance to produce the smaller scale maps with HRSI would be much higher as compared with aerial photogrammetry if the cost of HRSI is not much high. However, the current commercial price of HRSI is about two times higher than aerial photography according to the survey in Europe. The advantage of mapping with HRSI is much simpler than aerial photogrammetry and efficient in terms of mathematical modeling and the coverage area.

A trend of high frequent orbit such as FORMOSAT with several repetitions in a day would overcome the weakness of optical sensors against cloud coverage. In addition, high resolution SAR with 1m or less such as TERRASAR X may bring a breakthrough for real time mapping in the environment and disaster management.

Why yes?

In Japan, aerial survey with airborne digital cameras and airborene laser scanners is drastically increasing to produce larger scale maps with 1:2,500 and larger. DEM (digital elevation model) with 0.5 or 1 meter grid is being made from high resolution airborne digital cameras and/or laser scanners, while majority of grid size is 5m practically. In those countries which are controlled by military, aerial photography will be operated only governmental survey/ mapping agency with conventional analog aerial photogrammery with less budget limiting about five year interval of updating national maps. However non-military countries such as Japan, can apply any high technologies of airborne digital cameras, laser scanners, unmanned airborne vehicle (UAV) etc. for private and commercial purpose. Aerial photography with high resolution digital cameras is now operated with more than 80 % overlap for along and cross tracks, which can produce so called “true ortho-image”. “Pictometry” with a set of a vertical looking camera and four oblique looking cameras is being operated daily for a new market based on easily understandable geospatial objects. UAV will become a new tool to produce “bird’s eye view” for a local area mapping or monitoring. Particularly disaster monitoring will be a good application in Japan as Japan is a disaster prone country. In meeting such demands, aerial photography with various cameras and sensors is a “must” as HRSI cannot solve those problems.

Shunji Murai

Emeritus Professor, University of Tokyo, and
President, Japan Society of Photogrammetry
and Remote Sensing sh1939murai@nifty.com
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