SatellStitch: Satellite Imagery-Assisted UAV Image Seamless Stitching for Emergency Response without GCP and GNSS

Abstract

Rapidly stitching unmanned aerial vehicle (UAV) imagery to produce high-resolution fast-stitch maps is key to UAV emergency mapping. However, common problems such as gaps and ghosting in image stitching remain challenging and directly affect the visual interpretation value of the imagery product. Inspired by the data characteristics of high-precision satellite images with rich access and geographic coordinates, a seamless stitching method is proposed for emergency response without the support of ground control points (CGPs) and global navigation satellite systems (GNSS). This method aims to eliminate stitching traces and solve the problem of stitching error accumulation. Firstly, satellite images are introduced to support image alignment and geographic coordinate acquisition simultaneously using matching relationships. Then a dynamic contour point set is constructed to locate the stitching region and adaptively extract the fused region of interest (FROI). Finally, the gradient weight cost map of the FROI image is computed and the Laplacian pyramid fusion rule is improved to achieve seamless production of the fast-stitch image map with geolocation information. Experimental results indicate that the method is well adapted to two representative sets of UAV images. Compared with the Laplacian pyramid fusion algorithm, the peak signal-to-noise ratio (PSNR) of the image stitching results can be improved by 31.73% on average, and the mutual information (MI) can be improved by 19.98% on average. With no reliance on CGPs or GNSS support, fast-stitch image maps are more robust in harsh environments, making them ideal for emergency mapping and security applications.

Carrier Phase Dual One-Way Ranging Method Based on a Frequency Hopping Signal

“…Multiplying the fast Fourier transform (FFT) result of the local PN code by the FFT result of the baseband signal. The results were processed using the inverse fast Fou rier transform (IFFT) [27].…”

“…Step 3. Recording the maximum position and maximum value of the IFFT value [27] Step 4. Setting the local intermediate frequency as the center frequency point, record ing the IFFT results at a Doppler frequency offset of −12 kHz~12 kHz [27].…”

“…Recording the maximum position and maximum value of the IFFT value [27] Step 4. Setting the local intermediate frequency as the center frequency point, record ing the IFFT results at a Doppler frequency offset of −12 kHz~12 kHz [27].…”