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Messages - SP74

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General / Cesium 3D Tiles - Poor Overview Geometry & Texture Resolution
« on: October 18, 2018, 07:14:47 AM »

I have produced a number of Tiled 3D Models and output them in both Photoscan tiled format, and Cesium 3D Tiles.  The Cesium 3D tiled models have poor geometry and low texture resolution when viewed at a zoomed out overview zoom level.  It is only once zoomed in that the geometry and texture resolution are acceptable.  The models vary in size from a few hundred input photos to a few thousand.  All display the same issues.  I have also loaded the models into 4DMapper, and the again when zoomed out poor results are obtained.

The models have been output using a mix of Photoscan 1.4.4 & Metashape.  The only noticeable difference is that a back (un rendered) side of the mesh is now transparent, so the model disappears when viewed from the back.  I am viewing the Cesium models using the cesium viewer (via html/apache web server).  I have tried numerous optimizations for the Cesium viewer, with little changes.

I have attached side by side comparisons of the 3D models, with the Photoscan model on the left and Cesium model on the right.




We fly the vast majority of our projects with survey grade GPS using PPK method.  Whilst ee may have our GCPs and airborne photocentre coordinates in the same datum/map projection, they have been derived off different origins.  For example, a mine-site survey may have the airborne photocentres derived from a CORS network. Meanwhile the mine surveyors have tied their GCPs into a existing geodetic network, potentially derived many years ago using optical survey methods.  In remote areas, there may be decimetre level differences between these datums, most notably in elevation.

To combat this some additional parameters in the block adjustment are introduced to allow the translation (and/or rotation & scale) of the airborne data to fit the GCPs.  Block adjustment applications such as PATB & ORIMA allow solution of such parameters, and it  doing so may increase the solution accuracy for Photoscan.

At the moment the GCPs are used as check points to determine the magnitude of any systematic translations, which are then manually applied using excel to the airborne photocentre coordinates.

Best regards,

Stu Paisley.

Hi Alexey,

Sorry for the delay in response.  I have a point cloud with approx 2 billion points.  When performing manual edits or ground classification, the point cloud saves quite rapidly, certainly within minutes.  However it is taking many hours to save the point cloud when the Select Points by Color, followed by assign class tool.  My current point cloud has been sitting on 0% saving for 12.5 hours so far...  It will get there.

The point cloud is on NAS device, the machine is using < 4% CPU resources and 1GB of RAM.  There is no network traffic reported by the Photoscan process.


Stu Paisley.

Hi All,

I have noticed that for large dense point clouds;

a) The project is very slow to save if the point cloud has been modified using the Select Points by Color tool, followed by the Assign Class tool
b) The project saves at normal speeds if the point cloud edited manually, say using the Free-Form Selection tool followed by the Assign Class tool
c) The Select Points by Color tool does not complete if it is used a second time.  The user must save the project, restart photoscan & reload project for successful operation.

This has been observed at least since version 1.3.5

Machine spec

Photoscan Pro Version 1.4.2 Build 6204 (64 Bit)
AMD Ryzen Threadripper 1950X
Windows 10 Pro x64
2x NVIDIA GeoForce GTX 1080 Ti

General / Adding a new geoid model
« on: December 03, 2015, 08:52:47 AM »

Would it be possible to provide a tutorial on how to add a geoid model.  I have converted the geoid model for Australia (AUSGEOID09) to Geotiff, but it is not clear in Photoscan Pro how to add this as a vertical reference system.



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