Application of unmanned airship image system and processing techniques for identifying of fresh water wetlands at a community scale

摘要

Wetland ecosystems have complex habitat characteristics due to the wetland existing between lands and water bodies, however, satellite remote sensing images have normally mixed pixels because of their spectral characteristics of the riverine surface feature, and it is very difficult to extract the specific information of aquatic ecosystems. Hence satellite remote sensing images are hardly to match the demanding from scientists for their geoinformation researches in wetland investigation with a higher spatial accuracy. Unmanned airship low-altitude remote sensing system can resolve this technique problem. Recent advances in photo-geometry and relational technologies have facilitated the use of inexpensive digital cameras with the airborne remote sensing. And the ability of an airship would be enable it to obtain high-quality spatial images at a very high resolution by utilizing low-cost imaging instruments such as CCD cameras. Due to few landmarks existing within the wetland areas, we set artificially signs as the control points in the study area. In this study, we obtained the scanned high-resolution images (with the spatial accuracy of 0.13m in a grid) using the unmanned airship platform in the Honghe National Nature Reserve (HNNR) located in the Northeast portion of the Sanjiang Plain. Using the software -Unmanned Aerial Vehicle (UAV) CCD Image Processing System, we have mosaic automatically the aerial photographs, and we also have mosaic artificially the images used the software ENVI 4.3 based on corresponding image points between adjacent images. The study results indicated that the auto-processing method relatively was more efficient image processing however with a lower accuracy (with 4 pixels as the RMS error). It meets a demand of the large amount of data process and a relatively lower accuracy. The artificial process method relatively has a higher accuracy (less 2 pixels as the RMS error) however time-consuming, which may be applied to the image process with a high accuracy however less data. The mosaic- images is available to identify wetlands vegetation at a community scale, such as Populus davidiana, Betula platjphylla and Carex pseudocuraica, Carex lasiocarpa, Calamagrostis angustifolia. With the results from this study experiment, we can conclude that the airship images can be used effectively to identify complex wetland vegetation information at a community scale, it has a great significance for applying to both scientific study and practical purpose, such as wetland plant mapping, environment planning and landscape design of wetlands, wetland restoration and ecological protection, etc.