POD intensity display & issue

Hello Bentley Communities,
This post tackles with Pointcloud intensity conversion when creating POD file.
One of my partner that everyday uses & works on Pointcloud reported me critical issues on Pointcloud display into Bentley Microstation & Descartes.
It is not the first time, therefore we decided to look deeper into the data and we made comparative tests between famous pointcloud viewer or engine, namely
- Microstation
- CloudCompare
- Terasolid
- QT Reader

We performed that test using the same LAZ files as source. dataset is from MMS survey, using state of the art Lidar (Optech SG-1).
We can clearly notice that there is a pb with Pointools engine (and consequently Microstation & Descartes).

>>>see attached screenshot<<<

What is striking is that you can get a POD with good intensity display, and the following neighboor POD with bad display.

Please note that "AutoScale Intensities" option was always selected.

Eventually we tried to convert again the files where we've got the bad POD, but that time we didn't set "AutoScale Intensities" option.
Resulting POD is clearly better !



Our conclusion is that POD Creator and internal POD converter into Microstation & Descartes have issue when processing batch conversion. "AutoScale Intensities" option is not well handle since you can get better result with or without option, but at random !

If Bentley tech team requires sample data in LAZ, please don't hesitate to ask our company. It would help the communities.

Regards,

antoine

  • Hi Antoine,
    I have responded to your query in the Service Request ticket that your raised.
  • Hello Felix,
    I have uploaded 4 LAZ files so that you could make your own test.
  • HI Antoine,

    If you use the Auto-scale option when batch converting files to POD format it will alter intensity values for that batch. It attempts to equalise intensity across all the scans in the batch.
    If you were to take 1 of the scans from that same batch and convert it on its own you could see different results in intensity. The reason for this is that the calculated 'min' and 'max' intensity is taken from 1 scan and not a batch of scans . Therefore, when displayed together they would appear to be different.
    This is how the software is designed, and not a fault.

    I suggest that you have 2 options: Convert ALL scans in one batch, or if this is not possible just don't use Auto-scale.

    It was designed to address a problem that exists in terrestrial scanning where from one scan position to the next the change in sun/cloud cover, time of day, or other conditions can drastically change captured intensity.

    It would be useful to know if your Optech system does something like this in the initial processing step.. if so, then you know that there is no need to use this option at all.

    regards, Dan


    This is a test

  • HELLO,

    I would like to ask further question regarding that post:

    if you don't activate the autoscale intensity how can u quickly find the right setting for offset and range in Intensity display settings ?

    is there any tool to parse the pod and see where are intensity value ?

    should we apply any "Bentley" rule ? (how is the POD conversion ? how is intensity store in the POD format ?)

    I know why source data set is coded in 12bits for intensity, namely from 0 to 4095

    I also know that intensity values are changing on an interval around 50 to 500...

    antoine

  • 1) There is no tool.
    2) There’s no rule this is just set to user preference visually.
     In the Ribbon under Point Cloud tab select Settings. The shader setting dialogue will appear on the right. Untick Show RGB or change the Blending to Intensity only. Leave the Intensity Ramp set on Greyscale and  you can now Change the Brightness ur Contrast to suit your preference.

    3) In Pointools its stored with the project until you Export to a new POD similarly with MicroStation the value is stored in the DGN until you Export to a new POD and choose to export intensity as one of your export  options