Sorry if this is a bit off the core thread of using Reefmaster for the Sidescan mosaic for Archaeological mapping topic (Matt if you feel this is too far off topic feel free to pull it down)

I too have been using Side scan sonar to find and document shipwreck sites for a number of years (I use an old Klein 595 Side scan) but in addition to mosaic software I have started using Structure from Motion to document the specific sites. I feel this may also be of interest to some of the responders to this topic.

Basically it provides a automated way to get photo mosaics of the wreck/area of interest similar to the images below comprised of around 500 odd individual images



or




I have mainly collected the raw images as a swimming diver but have also collected the base images from a diver scooter and a small ROV

Sorry for the redirect but have a look at a thread at OpenROV on how I have been doing this if you are interested in the technique

Scott

Impressive stuff Scott - that is really cool!
So that is a full 3D photographic rendering of the wreck? How does the processing software stitch the images together - do you really have such precise information about the position/attitude of the ROV or does it use the match using the images themselves?

Yep full 3D rendering (you can sort of see it better in the top image which has more of an isometric view) and can export it as a xyz file (various formats)

They are all stitched by feature matching so you need about 60-80% over coverage from one image to the next

None of the images need to be geolocated the software (either Agisoft photoscan or VisualSFM) works it all out for you

We are just starting using this (photogrammetry) on some of the ancient wrecks that we've found. Now that processing power and memory are accessible to the common man this has become more of viable. Its great to see the results of it - these are very impressive images.
Do you use any base reference points (reasonably accurately positioned poles) or do you just use the object being photographed / filmed for your work?

T

Very interesting ROV!! That give me idees....
I was bilding a towfish for wreck which are too deep for side imagin but difficut to use , it is 80m deep. First I have done is only the transducer send near the botton, next I'm looking to do is to send battery+side imagin trancducer and humminbird card in an equi presure box full of oil an control it by Ethernet cable to my ONIX, can replace the towfish by ROV can be more esay to use and controle depth!!

AnglingCharts

RE computing power I'm just using a reasonable up spec'ed laptop (I7 plenty of memory that I also use for all of my post processing of all my hydrographic data MB/SSS etc) some of the data processing can take up to 20 hours (dependents upon the number of images)

I don't use any reference points for the software but for "running lanes" for the collection of images something giving an indication can be of assistance (eg the wreck of the Colonist in Sydney Harbour which is nothing more than an outline of Muntz metal). The software can handle georefferance points and then the output is in a world coordinate system rather than just a relative coordinate system



Nitro78

I have been think about that for a while as well you should have a look at the SV Seeker ROV build



A Towed fish is great for finding objects but the ROV is the way to go for documenting the wreck site (PS 80m isn't too deep for divers you can typically get 40min bottom time at that depth without too much deco)
Scott

Hi Scott

can you advise what software you are using for this please

Cheers Andy

Hi Andy

I have been using Agisoft PhotoScan www.agisoft.com/ although I believe that the lite version will provide the same results

I also have a few friends who have been using the open source VisualSFM ccwu.me/vsfm/ and have been basically getting similar images

Again back over at OpenROV/OpenExplorer in the background a number of us have been putting together a how to guide associated with this technique and expanding upon the basic how to in the original OpenROV link above that I posted. The Guide is in its final edit currently (about 8 pages). If Matt’s cool with it (it will have some OpenExplorer branding plastered on it) I can post a link to this guide here when it gets pushed to the net

Scott

thanks for quick reply Scott will take a look at both

Hi Felix, awesome pictures, thanks for sharing with us. :)

What type of cable do you use, and what length ?

hi dive explorer
i use ethernet cat 7 a cable, now 65 meters, hybrid system Lss2/hdsi and humminbird unit
i post topic in side immaging soft forum.

Yes of course, thank you I had forgot :)