your fans need your help:)

[gushangzao007]

Hi halmaia! I come back again.:)

I have a personal DIY project, and I want to know how to do some georefencing work for the SideScan Image exported from your greate software SL3Reader and GIS map as precise as possilbe.?

I've read your paper. however my knowledge is very limited,:). as far as I known, the route data of sidescan image is precise, but I have no idear how to get correct data for left and right groud range of sonar

[halmaia]

Hi there,

Yep, georeferencing a SideScan dataset is a little bit tricky and you have two options to do it:

1. Take the image and add ground control points to every tenth strip, one for the left, one for the center and one for the right. If you display the image in a GIS software, it will be curved to the path. I'm gonna implement this solution in the code in the next month or two and you just have to call a different command line argument. However, this solution is not perfect at all: the watercolum is included as the distortions as well. So this georeferencing is just an approximation.
2. A. Assume that the bottom is flat. In this case with some resampling it is possible to synthesize a new raster. Perfect for quasi-flat-bottom seas and lakes. I will try to implement it in the summer. B. Create a real georeferencing based on a real bottom elevation model coming from interferometric measurement. This will be the best solution. I have to do a lot of experimentation on it.

Best regards, Ákos Halmai

gushangzao007 @.***> ezt írta (időpont: 2024. febr. 2., P, 11:05):

Hi halmaia! I come back again.:)

I have a personal DIY project, and I want to know how to do some georefencing work with the SideScan Image exported from your greate software SL3Reader and GIS map as precise as possilbe.?

I've read your paper very hardly. however my knowledge is very limited,:). as far as I known, the route data of sidescan image is precise, but I have no idear how to get correct data for left and right groud range of sonar

— Reply to this email directly, view it on GitHub https://github.com/halmaia/SL3Reader/issues/9, or unsubscribe https://github.com/notifications/unsubscribe-auth/AEBCY4E72D36CG6JB2J7NULYRS3AJAVCNFSM6AAAAABCWM6DK6VHI2DSMVQWIX3LMV43ASLTON2WKOZSGEYTINJVGU4TMNQ . You are receiving this because you are subscribed to this thread.Message ID: @.***>

[gushangzao007]

Cool, thanks for your kindly feedback! my project is for fishing, which help fishing player to find structure under water ,So target sea area is around some island. average depth is 5~20 Meters.
In your opinion, for the first solution above, what is the approximate precision?

[gushangzao007]

another question, after I exported side scan image, I got a file named "SS_790.bpw" , I've no idea about:

1.what does "790" mean? 2.what does those 6 numbers in file mean?

---my eported file list SS_790.zip

[halmaia]

Hi there,

1. 790 is the ID of the last frame presented on the image, so if you check the exported route text file, the line with ID 790 belongs to the last strip of the image.
2. The bpw file with the six numbers is called a World File ( https://en.wikipedia.org/wiki/World_file). Even though the given SS is not georeferenced these lines describe the correct scaling, rotation and pixel size. Standard image viewers can't handle non-square pixels, but in the sonar world, the elongated pixels are quite common. So if you drag-and-drop an SS file into a GIS viewer (like the free QGIS) you will see the correct scaling. Check out this video: https://www.facebook.com/100006926054823/videos/2104897333084448?locale=hu_HU This clip is created from these SS+bpw files, just by dropping them into the GIS software. They automatically ordered and scaled and stitched together, based on these bpw files.

Best regards, Ákos Halmai

gushangzao007 @.***> ezt írta (időpont: 2024. febr. 5., H, 3:25):

another question, after I exported side scan image, I got a file named "SS_790.bpw" , I've no idea about:

1.what does "790" mean? 2.what does those 6 numbers in file mean? image.png (view on web) https://github.com/halmaia/SL3Reader/assets/11475854/e1ad6bca-e290-4033-b79d-2258e584397d

---my eported file list SS_790.zip https://github.com/halmaia/SL3Reader/files/14159784/SS_790.zip

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[halmaia]

Can you share a small, sample SL3 file to check the actual situation?

gushangzao007 @.***> ezt írta (időpont: 2024. febr. 5., H, 2:36):

Cool, thanks for your kindly feedback! my project is for fishing, which help fishing player to find structure under water ,So target sea area is around some island. average depth is 5~20 Meters. In your opinion, for the first solution above, what is the approximate precision?

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