Recently, the interest of Unmanned Aerial Vehicle application in photogrammetric environment for roads observation and monitoring has increased in many countries, in Lithuania as well. The experimental object for demonstration of capability and efficiency of aerial vehicle-based remote sensing technology for road data collection was a western bypass of Vilnius. The platform of the model UX5 Trimble with mounted camera Sony NEX-5R was applied for gaining images. The implemented means are mobile and not expensive. Photogrammetric technique with software package Business Center Photogrammetry Module was applied for the modelling of images. The correctness of digital surface model generally depends on camera resolution, flight height and accuracy of ground control points. The coordinates of control points were determined using Global Positioning System Trimble R4. Paper demonstrates results of a new technology application possibilities for linear object (road) mapping and accuracy evaluation of spatial models. The road points positioning accuracy investigation was carried out in consideration with geodetic control measurements. The average root mean square error for the points coordinates is 2.94 cm, and standard deviations – 2.78 cm. Analyzing coincidence or mismatches of Vilnius western bypass project data with photogrammetric product, not significant discrepancies of road section features were determined. The cost consideration of Unmanned Aerial Vehicle in conjunction with photogrammetry employment at experimental object is presented.
ABSTRACT:The Low-cost Unmanned Aerial Vehicle (UAV) has been used as a platform for photogrammetric data acquisition. Two techniques were accepted for mapping. One is remotely-piloted aircraft with mounted digital camera Sony NEX-5 for low altitude photogrammetry. The flying height was about 30 m. Another is close range photogrammetry taking images from building -geometric situation similar to aerial case (vertical images). The Trimble R6 GPS has been used for determination of ground control points coordinates exploited in exterior orientation procedures. DTM's creation via image matching and area mapping was performed by software LISA designed at University of Düsseldorf. Comparison analysis of applied two techniques efficiency and application possibilities has been carried out. The accuracy assessment is given. The residuals in x and y at every point and standard deviation in exterior orientation procedure of images from UAV platform is about half of pixel size referring to the image, i.e. 0,14 mm. Experimental accuracy investigation regarding UAV and GPS data shows that maximum absolute planimetric displacement is 0,25-0,30 m. Such data fulfils the accuracy requirements for large-scale urban area mapping.
The knowledge of physical processes and changes in the atmosphere is essential when addressing the fundamental problem, i.e. the accuracy of geodetic measurements. In levelling operations, all these changes are explained as the effect of refraction, which systematically distorts the results of levelling. Different ways of addressing the effect of refraction are represented based on the modelling of the vertical temperature gradient as the quantity that has the most influence on the refraction phenomenon.
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