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Water Mosaic

I need to fly some scenes with water only, no land. EbEE+ with Sequoia or SODA. Accuracy is not important (20 m). I have no land. I just need each picture to be corrected for pitch, yaw, and roll and to locate the pictures via GPS so I can look for features manually in the water. No other products but a stitched together image OR individual images with geolocation.

The eBee and Pix4D will produce wonderful geo-ortho-mosacs, the issue is key point or automatic tie point generation will suffer greatly due to the water chaotic surface motion obscuring bottom surface patterns.

Light angles most be just right to get the best bottom contrast as possible.

Even with best condition ( good light angles, clear stable water and shallow depths) this will be challenging.

 

Hi Stuart,

As Gary points out, it is a very challenging project. Having no land makes the process very difficult.

The recommendation for this particular case would be to fly with the highest overlap possible and trying to capture the images with the best contrast. This would help the software to get keypoints but matching them will be still very difficult as the water is moving.

More information on generating orthomosaics of water areas here.

 

Regards.

Is there a way just to get an approximate location for each image from the GPS coordinate, and pitch, yaw, and roll corrected data? Basically, to approximately geolocate each image over water if not a nice mosaic?

Yes! Typical most airframes that have integrated sensors and navigate via GPS (DJI) will geo-tag imagery during mission. In other systems, a file is generated containing gps log data that Pix4D uses to geo-locate imagery collected on mission.

I wouldn’t bother processing in Pix4D, 99% chance it won’t work unless you have clear underwater features in each image.  I have done plenty of water images…

Best bet is to see if ArcGIS or something that will make an orthomosaic with all geotag info and no feature processing

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Thanks Adam, super helpful. So should I remove the distortion (pitch yaw and roll) from the images in Pix 4d and then bring into Arc?

HI Adam and Stuart,

It is not Pix4D, any software which applies matching algorithms in the water will fail unless it has some texture.

If your dron is able to provide x,y,z,yaw,pitch and roll as geotags, maybe it is better to use them directly without any process. However, bear in mind that the final accuracy will be the same as the geotags and if they are not precise, the final mosaic might have discontinuities.

For cases like this, having precise geotags (RTK/PPK drones) helps a lot.

Regards.