Mavis 16.9.0

Mavis 16.9.0 is available.

Amining to provide the best orthomosaics possible for your application, this release focuses on enhancements in orthomosaic generation. The methods implemented in Mavis comprise blending, locally adaptive exposure compensation and illumination correction.

While blending is aiming at joining two neighbouring images seamlessly, exposure compensation corrects changes in the colors due to changes in weather conditions and thus camera exposure settings, and illumination correction adjusts the combined effects of vignetting, BRDF illumination differences as well as over- and underexposure effects resulting from changes in brightness across the image.

The influence of exposure differences is most visible in image sets where strong changes in weather conditions occur during flight. These can result in changes in aperture, shutter-speed and ISO settings and thus color and brightness gradients across the orthomosaic.

To provide optimal results Mavis combines blending as well as local adaptive exposure compensation and illumination correction techniques. This results in sharp and high contrast orthomosaics.

All orthomosaics shown in the following are generated with different settings in Mavis to visualize the influence of the methods and their combinations. All data shown in the figures are raw image data (DN) without any pre- or post-processing (gamma adjustment, white balance, contrast enhancement, etc.) applied to the input images or the orthomosaics shown.

The first image is a raw orthomosaic without any algorithm applied. The seconds shows the effect of exposure compensation and the third of exposure compensation and illumination correction. In this third orthomosaic only a very few remaining seams between the single images remain visible. The fourth shows the result of blending without any other technique applied. The last image is generated using the default settings in Mavis with all approches integrated.

 

Orthomosaic_00

Fig. 1: Raw orthomosaic without blending, without exposure compensation, without illumination correction

 

Orthomosaic_00_10

Fig. 2: Orthomosaic without blending, with exposure compensation, without illumination correction

 

Orthomosaic_00_10_05

Fig. 3: Orthomosaic without blending, with exposure compensation, with illumination correction

 

Orthomosaic_blended

Fig. 4: Orthomosaic with blending, without exposure compensation, without illumination correction

 

Orthomosaic_04_01_05_2020

Fig. 5: Orthomosaic with blending, with exposure compensation, with illumination correction (Mavis default settings)

 

For illumination correction illumination errors are computed for each images. The following image shows three single orthoimages of the above example, their corrected versions as well as the corresponding illumination errors.

 

Images_masks

Fig. 6: Single ortho images, their corrected versions and the illumination error masks

 

The following two orthomosaics show the limitations of pure blending approaches. Both mosaics have been postprocessed in Mavis with the same enhancement settings (without contrast enhance). The first one shows the version solely based on blending, whereas the second one is based on the default settings in Mavis including illumination correction and exposure compensation. The blended version shows a much lower contrast.

 

Orthomosaic_bl_enhanced

Fig. 7: Orthomosaic using blending

 

Orthomosaic_enhanced

Fig. 8: Orthomosaic based on the Mavis default settings

 

With changing weather conditions the differences are not only visible in contrast as in the above example but also in color. The next example shows the differences between a raw unblended orthomosaic and the final orthomosiac with blending, exposure compensation and illumination correction. 

 

Orthomosaic_raw

Fig. 9: Raw orthomosaic 

Orthomosaic

Fig. 10: Orthomosaic with Mavis default settings

 

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