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