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Pix4D Mapper Question for large sites - Help  

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StLSurveyor
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(@stlsurveyor)
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I flew a site yesterday that contained nearly 1650 images, which covers about a third of the overall site. I processed the mission last night and all went well, no errors. The overall orthomosaic image is 1.7 GB in size which is too large for my photo viewer software and C3D, so I attempted to save the file down to 20 MB by using InfraView 64, which when doing so trashed the quality of the ortho and makes it worthless. The output format I selected in P4D is TIFF. 

 

Does anyone have some experience/advice on dealing with large scale site in P4D where the output ortho can be useful? 

 

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(@chris-mills)
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TIFF's tend to be around 10 times the size of a JPEG. If you can save as a JPEG it should be suitable for most purposes (such as acting as a backdrop to assist extraction of string data into a survey package). I'm assuming that PIX4D can now produce JPEGS. If you need to make an ortho smaller then do so at the processing stage by selecting a lower grade, rather than trying to shrink the image you have already produced. The largest we have produced was 7000 photos - at medium resolution it was fine (using Photoscan). On large areas it is unlikely that the client will need all of it at high resolution, so you could produce high resolution models of the critical areas.

Other option would be to produce the TIFFs for smaller areas, so you end up with blocks. In that case either create overlapping blocks or set the block size so you can load them up in 2x2, so you can always move off one and on to the adjacent one.

Hopefully in a couple of hours Lee G. will come up with a more sophisticated solution.

 

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(@prairie_surveyor)
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You have a couple options here;

If you wish to keep the current resolution one would be to use a program like Global Mapper to tile your mosaic into specified sizes, ie 1kmx1km, it associates a world file with each tile for easy import to your software.  You can also manipulate the sampling with it which reduces the file size, ie 2cm to 10cm

A second option is to look into the ECW or SID file compressions;  

I have have a flight image of about 1gig (2.7cm res) - using global mapper and exporting the mosaic to ECW the file size reduced to 73mB.  Using GM and reducing the sampling from 2.7cm to 10cm the file size reduced to 88 mbs.

hope this helps.

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thebionicman
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A definite second for ECW compression. It makes the files managable with no loss of product quality. Global Mapper is your ticket...

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StLSurveyor
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Well...But I did find that in Infraview, under Image/ResizeResample - I decreased it by a factor of 10 and then Save As a jpeg the quality was maintained well enough for this purpose. Just wish Pix4D could do this internally. It is so frustrating that software like Pix4D doesn't really consider the end product. 

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(@prairie_surveyor)
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You wish to reduce the resolution within Pix4D?

That's easy enough, under the DSM and Ortho menu, set the resolution to custom and enter your desired resolution for your mosaic.

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StLSurveyor
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I will try that, and play with that option when we run the next phase of the mission. Large scale project in P4D are new to me. The overall site is about 725 aces and will probably be 4000-5000 pictures. I am sure it will take some time to know a good GSD. We are flying at 380 FT AGL. I will play with the numbers - sucks though that it takes P4D over two hours to process, even with my i9 10 core processor. Lots of waiting around to see if it works. What would be sweet is a slide scale that would tell you approx. output size as the change the GSD in P4D.

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