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Thursday, January 17, 2013

Story of the world's most detailed aerial image


Written exclusively for the HUNAGI blog by Gábor Bakó PhD student, Interspect Research Group, Hungary:

How the world’s most detailed aerial image was made


The world’s most detailed aerial image mosaic has been made. Aerial photos have been used for mapping in Hungary since 1916. The unique feature of the ortho image map made in 2012 is its amazingly high resolution. A pixel is suitable for displaying units of half a centimeter width. No one has managed to reach such a high level of detail covering such a big area from a fast moving aircraft.
Not only specially modified aircraft and specially designed sensors are needed for the purpose, but it also requires thorough planning and careful implementation. This method is suitable for various ecological and climate research investigations which also contribute to the significance of the Hungarian world record. The key feature of the new technology is high spatial resolution. The resolution of the best black and white satellite images is 40 times lower while the resolution of infra-red images is three hundred times lower. Images of five times lower resolution have been made from aircraft in other countries.






Four specially calibrated aerial cameras were built during this period, making possible detailed environmental surveys that had been completely impossible previously. The photographers were inspired primarily by these applications. This is the main focus of the research work.


Not only laboratory preparations were involved; the equipment was also tested in various aircraft. Tests were conducted in the years preceding development of the sensors; as a result the first Hungarian digital aerial cameras were built. After modification of the aircraft and planning the flight, the crew had to wait for the most suitable time. The right weather is crucial, as even the shadows of clouds can be disturbing if they are visible on the image.


The flight was planned by the owners of the idea: the ortho photo operator Gábor Bakó, András Arady first pilot and Zsolt Molnár.




Although detailed high resolution aerial images had been made before from helicopter and ultra light slow flying craft the basic idea of ortho image mapping is to make economical and quick flights covering large areas. The aircraft moves fast, covering the paths of the area, while the aerial camera looking downwards makes shots of the Earth’s surface. The map is made from these continuous overlapping shootings. Ortho images are generated by processing the digital photos. These orthophotos are cartographic projection-matched images, with geographical coordinates assigned to every pixel. Harmonization of the partially overlapped orthphotos results in a photo map. It is a photo which displays the surface of the Earth in the map coordinate system. This also requires field measurements, and clearly set control points on the ortho-photo. The measurements are made by high-precision geodetic GPS. These coordinates assisted the cartographic projection and synchronization of the image with the earth surface displayed. The digital image generated conveys a great deal of information about soil types and humidity content of open areas, about the composition and extent of any pollution. Vegetation can be mapped, and the state of natural treasures can be recorded in space.
The Military Memorial Park of Pákozd was declared a National Memorial Place by the Hungarian Parliament in an act of 1 January 2012. The Memorial Park is designed to present the heroism of the Hungarian soldiers witnessed in the past 165 years, starting from the first winning battle of the fight for liberty, for protection of the achievements of the 1848-year revolution. The Memorial Park is the most frequented exhibition site of the region which receives visitors from March to November.

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