PRELIMINARY INVESTIGATION ON POSSIBILITY OF SUPER RESOLUTION OF UAV ORTHOIMAGES
Since inspection of infrastructures using UAV images seems to be efficient, many systems for infrastructure maintenance using UAV images have been developed recently. For the purpose of more efficient image acquisition, we started an investigation on the possibility of super resolution (SR) of UAV images to obtain high-resolution (HR) orthoimages suitable for infrastructure maintenance. This paper reports an preliminary investigation using existing UAV images acquired for 3D measurement that were not be intended to be utilized for SR. We produced HR orthoimages by three SR methods: image interpolation of a single low-resolution (LR) image by cubic convolution, SR by resampling, and SR based on observation equations. Both SR by resampling and SR based on observation equations utilize multiple overlapping LR images. Results of the investigation demonstrate that SR based on observation equations using multiple overlapping images would be able to provide higher resolution orthoimages than those produced by an ordinary method. The results show that an inaccurate DSM utilized in SR processing degrades the quality of SR results as well. Furthermore, the results illustrate that the quality of the result of SR processing depends rather upon the characteristic of a lens utilized in image acquisition. We think that further investigations on SR using UAV images would be necessary in order to put SR to practical use.