Research on the application of ultra-small scale color IR Aerial Photography in investigation of renewable natural resources and environment
Yu Xianping
Department of Remote Sensing of Environment and Resources,
Research Institute of Forest Resource Information,
Chinese Academy of Forestry
Abstract
The paper introduces the present situation of application of ultra-small scale color IR aerial photography, and analyses its spectral resolution, spatial resolution, integrated resolution, thematic presentation capability and cost, to investigate the technical and economic properties of its application in survey of environment and renewable natural resources.
The study shows that the application of ultra-small color IR aerial photography has a bright prospect.
Aerial photography has got more and more wide use due to the rapid development of social economy and due to the increase of application demand. However, there is now a tendency worth discussion in the application of aerial photography, i.e. the scale becomes more and more large, which evidently needs more cost.
An unnegligible principle of aerial photography is that the accuracy needed for research and application is the key factor for selecting the appropriate scale. In fact, in most cases, the abundant information of airphotos is far beyond enough exploitation and utilization in application.
Based on the above-mentioned reason, the paper mainly discusses the application of ultra-small scale color IR aerial photography, and evaluates its applicability and economical benefit. This would help to make a proper choice of the scale of the airphotos, and to understand the potentials of such ultra-small scale photography, as well as to expend the application of such aerial remote sensing imagery.
The ultra-small scale aerial area photography at the scale of 1:130000 was taken in somewhere, Hebei Province during the implementation process of the key scientific project in the Seventh National Five-Year Plan, the Comprehensive Investigation of the "Three Norths Protective Forest" by Remote Sensing, and thus started the prelude for the application of ultra-small scale color IR aerial photography.
At present, the aerial photography at the scale of less than 1:100000 is called ultra-small scale
Aerial photography. The domestic and foreign references, and the application conditions shows that neither the information potential of the ultra-small scale color IR aerial photography has been systematically quantitatively measured, nor the application technology investigated, nor the application experiment in operational scale has been made. In general, its spreading prospect is still in a state of obscurity.
This study has made an analysis with the photos taken in somewhere, Hebei Province as examples, which are color IR aerial photos of the scale 1:130000 to investigate the potential and prospect of its application.
Spectral Resolution
The color IR aerial photos of the scale 1:130000 taken is somewhere, hebei Province in 1986 have excellent visula interpretation results. The images possess sufficient clearness and chromatic saturation even after linear magnificaion of 25 times (the enlarged images have a scale of about 1:5000).
On the ultra-small scale color IR aerial photos enlarged to the scale 1:5000, all the ground types and objects including various tree species can be identified according to their color and other image characteristic.
Chinese pine, black locust, poplar, oak, apricot tree, orchard tree, shrubs, barren land, farmland, road, water body, can be identified. In addition, the shape and size of the smaller objects (e,g. residential houses, small ponds) can also be clearly distinguished.
The density of various objects on the image is also an impotent indication to their spectral characteristics, and is significant for identification of various objects. The study showed that the density difference between objects on ultra-small scale color IR airphotos is obviously larger than that of corresponding objects on standard false color composites of space imagery including SPOT, LANDSAT-TM, MSS. It is evident that large density difference favors visual interpretation of objects. Therefore, different tree species and other objects that possess relative difficulty for visual interpretation cn be relatively easily distinguished according to the differences of their spectral characteristics on ultra-small scale color IR air -photos.
