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Georeference Orthofacade

Hello. I’m wondering if it’s possible to georeference an orthofacade. Could I, for example, attach targets to the facade, collect coordinates for them as I would with conventional ground targets, and use those to apply georeferencing to the orthofacade?

I know in the orthofacade generation documentation it says the orthofacade will not be georeferenced, but I was wondering if there was an optional way to do this.

If not, has anyone successfully georeferenced an orthofacade some other way? I’m thinking I could take the mosaic into ArcMap and apply georeferencing there if there’s no way to do it in Pix4D.

Curious to hear peoples’ thoughts on this.

Hi @Arktix,

Importing a georeferenced orthofacade in ArcMap wouldn’t it result in a line?
What do you want to do with this georeferenced orthofacade?`

I have heard that some users were tricking the software by flip xyz coordinates in order to have the cameras of the ortho looking down so when processing they got a georeferenced orthomosaic but with the coordinates flipped. They were most doing this because they wanted to use the mosaic editor to improve the ortho.

Best,

I do think it would result in a line, so I think we’d have to do something like you suggested and transform the coordinates to trick Pix into thinking it’s flat on the ground. Might be easier to bring the un-referenced image into arc and then add the fake coordinates there.

What we’re trying to do is inventory a bunch of small cracks in a levee wall. The vertices of the polylines tracing each crack need to be georeferenced to a known coordinate system.

Hi @Arktix,

Then you might be interested into our new product: Pix4Dsurvey.
It allows to create vectors from point cloud based on the images (if exported from Pix4Dmapper).

I recommend you to have a look on this thread:

And I would recommend you to try it! (It is highly recommended to test it with the demo project to get an idea of the possibility of the software).

Best

Thanks for the suggestion. We’ll look into Survey. However, the 3D model inside survey still won’t be georeferenced, will it? In the end I have to have all of my polylines be georeferenced to a known coordinate system.

Hi @Arktix,

They are georeferenced since they are made from a georeferenced point cloud! If you import your project from Pix4Dmapper, you will have the possibility to draw your lines in the point cloud and the move the vertices in the images.

Imagine you have something like this:

image

And then you import it in Pix4Dsurvey.

Here an example with the demo data set:

You can draw having the images next which facilitates the vectorization.
That’s not the best example I admit, but then you will be able to draw your cracks and export your lines as *.dxf.
You should give a try. It might fit your needs. You only need a license to export the file. But you can get a trial ;).

Best

Oh excellent. Thanks for your suggestions. We’ll have to give Survey a try for this project.

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Could someone help me understand how Pix4Dmapper makes use of multiple cameras? We did a test of the orthofacade workflow and have a tif of the wall we’re trying to look at, but the 20MP camera on our Phantom 4 RTK isn’t giving us enough resolution to see the hairline cracks we’re trying to look at. I took photos progressively closer and closer to the wall until I was 10-15ft away and it’s still not enough resolution to fully make out the cracks!

If I added in photos from a DSLR (for example, a 42MP Sony A7Riii) will Pix4Dmapper maintain that higher resolution on the wall face even though most of the photos will come from the 20MP camera on the P4R? What does Pix4Dmapper do when given photos of different resolutions?

Hi @Arktix,

If you want to calibrate different cameras models, then do it in separate project and then merge them.
Create a project with the different cameras models, process the first step and then merge them using MTP/GCP.
More here:

It mostly depends on the GSD of your acquisitions. It is recommended that the difference does not exceed two times.

Hope this help.
Best

So if I do one project for my aerial drone imagery and one project for terrestrial handheld high-res DSLR imagery of the wall face will the higher resolution of the terrestrial imagery be preserved in the merged project?

Hi,

It should since the point cloud generated from the high res camera will keep the same resolution when merged and will be densified during the second step.

Best