Sea Mapping

I would like to map beach area and I want the map to include also water areas (in order to map some underwater structures) however when I produce maps the land areas are mapped but everything from the water line is not mapped instead webodm use the google maps to fill in these areas.
can someone pls advise how can I make webodm to use my images for those areas as well?

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Water is very difficult to reconstruct.

See this thread for discussion:

I think one of the conditions for producing any kind of stitched images - are unique features present in multiple overlapping images.

If the water in question is just a plain surface - without say a lot of surfers, boats etc - most software likely have no clue on how to allign the images precisely. GPS mid point readings won’t be enough…

Give it a try if you can fly over a piece of water with a lot of objects - and see if it indeed makes a difference.

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Correct. Extracting tie-points from homogenous features is more or less impossible. Spectral surfaces like water, glass, snow, ice, etc. are incredibly difficult to extract good features from.

Compounding that is the fact that the water’s surface is likely changing significantly between each frame acquired, again leading to issues with finding tie-points.

Is there any other software which I can use for producing aerial photo/map that includes GPS coordinates ?

OpenDroneMap does use GPS coordinates for reconstruction, but again, over water is going to be exceedingly difficult.

You can try a naive 2D non-georeferenced reconstruction if all you need is an orthophoto using something like Microsoft Image Composite Editor.

My suggestion of using surfers was really bad b.t.w. you need STATIONARY reference points. An anchored boat is better, but may drift a lot between passes. Only workable objects would be lighthouses, piers, limiting you to smaller harbours.

If you need water close to the island, in bays and mangrove areas, one possible solution may be to fly higher, capturing more land mass to help the stitching process. Then, as suggested, use Microsoft ICE to stitch. If you do not need DSM’s 3D models that may be a quick fix.

The orthophoto produced will have some minor aspect issues, so it can not be used for very precise coordinate extraction. (You will see a bit of the sides of buildings - in a true orthomosaic you will not, as all points on a vertical line have the same x,y coordinate.)

If the drone can carry a camera with a true high resolution sensor, that may help on details

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Give a free trial of Metashape a try - I use it for 3D models to compare with WebODM.

The basic version of Metashape is only a few hundred USD; is more stable than WebODM, but also a lot more restricted - now DEM/DSM etc.

One advantage is direct export to 3D PDF files for distribution.

well I don’t really need 3d , I want to use if for fishing , so i can map underwater reefs and identify their coordinates

I think you need a different drone for that:

Or talk to @kikislater who has been doing this for a few years. :smiley:

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mm how can i find him?

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Search for that username. Sylvain is here on this forum.

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Does using a polarized filter helps in detecting underwater features? Is it worth to try?

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It may, if you get the angle right… Should help with reflection, too

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Yup. Also, putting the camera on a wind surfing board or paddleboard or similar works even better.

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