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Contributor
Posts: 36
Registered: ‎05-02-2018
Accepted Solution

Generate DSM with SGM module on photogrammetry

Hi everyone,

I've got some Tri-Stereo Pleiades imagine covering a large area (so I've got several Tri-Stereo), I would like to generate a DSM of the total area then, an orthophotography.

I made a photogrammetry block, compute the interior/exterior orientation, generate Tie Points automatically (APM) and did the Block Triangulation.
Now, I would like to generate the DSM to construct a great Orthophotography then.

When I select the SGM module, "Tridicon Semi-Global Matching (SGM)", all of my "Image Pair" are indicated on "Status" as "Not Ready". Why ? How can I fix this ?

When I click on "Not Ready" several options are proposed :

"

Create Intermediate Files For:

  • One Pair Selected
  • All Selected Pairs
  • All PAirs Without Needed Files
  • All Paris (Rebuild All)

"

 

which one should I select ? "All Pairs Without Needed Files" seems to be the best option. By the way, when I select this, I've got an error message Warning me about the memory of my computer : "There may not be enough disk space for XXX, which is estimated to need 1 Go, 937 Mo, 414 Ko more. But I have 700+ Go free.
Is that a bug and so, should I skip this warning message and compute the intermediates files ?


Thank's in advance for your answers !

Staff
Posts: 130
Registered: ‎06-30-2016

Re: Generate DSM with SGM module on photogrammetry

"All Pairs Without Needed Files" is the right option if you are going to generate point clouds from all the images. 

 

As for the size, do you have several drives? It only checks size availability on the drive that you are saving the output pointcloud. 

 

Best regards, Sam

Contributor
Posts: 36
Registered: ‎05-02-2018

Re: Generate DSM with SGM module on photogrammetry

Thank's for your answer,

I have two  hard drives but everything is saved on the second hard drive. I also install Imagine on the second HDD with 750+ Go. My first hard drive have only 30 Go left. Could it be possible that imagine use the HDD with system by default ?


On the "output" tab of the SGM module, the "E:/" drive is the HDD where the output will be saved, and it's the good HDD. After removing big files on my E HDD, I get exactly the same message with the same amount of needed memory. Doing the same thing on my system HDD, I get, again, exactly the same error message.

 

Best,

Staff
Posts: 130
Registered: ‎06-30-2016

Re: Generate DSM with SGM module on photogrammetry

How about doing a small test? Make only one Tri-Stereo (three images) active and see if you get the message.

Contributor
Posts: 36
Registered: ‎05-02-2018

Re: Generate DSM with SGM module on photogrammetry

I disactivate a Tri Stereo, so they disapear on the SGM window but, I still get exactly the same message with the same amount of memory required.

 

The message speak about one file: "XXX_0_1_m.tif" so maybe, the number of tiff file in input will not change this error message because it is only about one file ?

Staff
Posts: 130
Registered: ‎06-30-2016

Re: Generate DSM with SGM module on photogrammetry

It may be writing intermediate files to the temp folder. Change the location of the temp file folder in the preference editor to a folder on the large drive.

 

The temp file folder can be changed In the Preference Editor -> User Interface -> User Interface && Session -> Temporary File Directroy

 

Regards, Sam

Contributor
Posts: 36
Registered: ‎05-02-2018

Re: Generate DSM with SGM module on photogrammetry

I change the temp folder as you suggest it and it worked like a charm.

So I could run the SGM tool, but after that, no DSM was generate. Is that normal ?

Staff
Posts: 130
Registered: ‎06-30-2016

Re: Generate DSM with SGM module on photogrammetry

A folder named SGM will be created next to the block. The DSM (in LAS format) will be in this folder. Is that not th case?

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