Is it possible to process & create point cloud data of inside a manhole?

PIX4Dmapper PIX4Dmapper Questions/Troubleshooting
1

Is is possible to process & create point cloud data of inside a manhole?

I want to take pictures of inside of a Manhole and then process in Pix4d and create a point cloud.

The photos won’t have a geotag position.  Well I if I lowered a camera from center position of the manhole, then I could create geotag and which all photos would have same lat long with different elevations.

If this is possible, what processing template I should use? and what proper way to take photos in field to make this work.

My end result, I want to be able to create point cloud of the inside of the manhole and have the ability to accurately measure the pipe sizes and height below top of manhole rim, to calculate the invert elevations of the pipes.

I am trying to have a solution for the products I all ready have. ie. Pix4d mapper.

I have seen that there is software out there specifically for manhole inspections using scanners and photos.

Thanks,

Anthony

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Hi Anthony,

In some way acquiring the dataset is similar to the one for the tunnel reconstruction where the biggest challenge is the lighting conditions. This is why we recommend:

  • Use a fisheye lens camera.
  • Take images in more than one line (avoid single track shooting). If a multiple tracks image acquisition plan is not possible, a single track could work. GCPs are highly recommended in this case.

It is possible to use the images without the geolocation but then the project would need to be scaled and oriented correctly in order for it to be suitable for measurements. This can be done by introducing GCPs or scale/orientation constraints. More in the following articles:

The best processing template would be the 3D Models as it is optimized for the oblique and terrestrial datasets.

Best,

3

I modeled a lift station without putting the camera inside the structure. I used magnetic lights under the lid to illuminate it. Also be sure to get your exposure correct. I used manual mode and shot in raw. I then used Lightroom to balance out the highlights and shadows. I scaled the project with the lid dimensions and was able to measure all of the items location and size very accurately. 

Next time I am going to try my 360 camera on a pole. I will lower the camera into the structure on one side taking pictures on the way down and then come up on the other side taking pictures. The trick is to know the dimension of at least one object to scale it correctly. Manholes are standard sizes, so you could scale off the inside diameter easily. Geo-tagged photos not required. Just make sure you have a good calibration for the camera you are using.

-Tommy

 

 

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Hi Tommy, Are you still doing this? Is it worth the time to do on roadway surveys? I’m kinda sick of trying to decipher field crew survey notes and it takes longer than the time it takes to actually pop the lids, take the measurements and the sketches. Interested in your response - thanks.

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James,

We are not using photogrammetry anymore for “close quarters” surveys. We are using the Trimble X7 Laser Scanner and Trimble SX10. The X7 can be mounted upside down and lowered into the hole. 4 minute full dome scan with pictures and the point cloud is done. No processing required. Going from 1 hour to 4 minutes per manhole is a game changer. The only photogrammetry we do anymore is for rooftops and large sites.

-Tommy

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Hello Tommy, Have you tried Pix4Dcatch app? It might be useful for your application.