¶ Optimisation
PCS software requires optimisation for each LAS file loaded into PCS to reach the points for visualisation quickly. Not performing the optimisation or willingly excluding it from the process will drastically lower the work speed with the software.
There are multiple ways to optimise a point cloud in PCS:
1. When the user loads the cloud, the optimisation type can be selected from the pop-up window (if defaults are not set)
2. The user can select Batch point cloud optimisation from the Tools menu and select multiple files for optimisation
3. Use the external optimiser tool.
In most cases, the optimisation will modify the LAS header and append extra information to the VLRs. In case the user is not allowed to modify the LAS file itself - as it might be a deliverable - please choose the respective option described below.
A detailed explanation of each optimisation process can be read below:
- After the installation of the software, it will ask the user for every point cloud file what the user would like to do with the cloud (if the setting has not been set to default before). There are five options:
- Do not optimise (or already optimised) - This option will not optimise and open the cloud. If the cloud was not optimised before, it will open as not optimised, and it will highly reduce the performance of the software and may also result in graphical glitches. If the cloud was optimised before the opening, it will open as an optimised cloud.
- Rearrange points(quadtree) and VLRs - This is the normal optimisation process when PCS optimises the clouds in the background. The optimisation will modify the LAS header and include additional information to the VLRs. If the optimisation has been performed before, the software will open the cloud without optimising it again. In this case, the optimisation will create a .bak file next to the LAS file, which will have the same name and size. This is the backup of the original LAS file, and if the user renames the .bak extension to the .las extension, it will result in the original file. In 99% of the cases, this file shall be deleted after the optimisation as it occupies a lot of disk space. Other auxiliary files will appear, but these will be removed once the file is optimised. Do not delete these files during the optimisation; this would corrupt the process. This method will result in the fastest use of an LAS file in PCS. While the software works on the optimisation, the software window will freeze. There is no progress bar. If the software window unfreezes, the optimisation has been finished.
- Rearrange points(quadtree) and auxiliary file *.lasbxs - This option will rearrange the indexing of the points inside the LAS file but will not include the VLR information in the LAS file itself. Instead, it stores it in a .lasbxs file. This method will result in a slightly slower use of an LAS file in PCS than the previous option. While the software works on the optimisation, the software window will freeze. There is no progress bar. If the software window unfreezes, the optimisation has been finished.
- Rearrange points and auxiliary file *.lasbxs - This option will rearrange the indexing of the points but will store the indexing information and the VLR information in the .lasbxs file. This method will result in an even slower use of an LAS file in PCS than the previous option. While the software works on the optimisation, the software window will freeze. There is no progress bar. If the software window unfreezes, the optimization has been finished.
- Auxiliary file *.lasbxs - This option will create a .lasbxs file but does not perform any optimisation. The created .lasbxs file will help PCS to use the non-optimised file. This method will result in a slower use of an LAS file in PCS. While the software works on the optimisation, the software window will freeze. There is no progress bar. If the software window unfreezes, the optimisation has been finished.
- If the user selects the "Set as default" option, the same settings will be applied to all LAS files which will be opened. PCS will ask the user to select an option for every LAS file if the setting is not set to default. If the default is set and needs to be changed, this setting can be accessed from the File menu/Las settings.
- Points in memory - A part of the points in the memory - This is the default setting; in standard cases, it is recommended to keep it as default. That way, the software will load only as many points as it needs. Classification tools are unavailable if this setting is being used.
- Points in memory - All points in memory - This setting will load all points of the point cloud to the memory and enable the classification tools. Please note that it is impossible to load more GB of LAS files to the memory than physical RAM can be found in the PC (for example, if 40 GB of LAS shall be loaded, but only 32 GB of RAM is installed in the PC, the software will crash. It is also recommended not to cover all physical RAM with point clouds as PCS would occupy most of the RAM, and the system would get sluggish).
2. If the user would like to perform the optimisation from PCS for a whole folder, it can be done using the Tools/Batch point cloud optimisation option. In this case, select a folder, and PCS will optimise all LAS files within the folder. This function will not optimise LAZ files. In this case, the optimisation will create a .bak file next to the LAS file, which will have the same name and size. This is the backup of the original LAS file, and if the user renames the .bak extension to a .las extension, it will result in the original file. In 99% of the cases, this file shall be deleted after the optimisation as it occupies a lot of disk space. While the software works on the optimisation, the software window will freeze. There is no progress bar. If the software window unfreezes, the optimisation has been finished.
3. The user can use the optimiser tool. Find the detailed explanation of the tool here.
¶ Trivia
- The optimisation is recommended during off hours, like evenings, lunch breaks, and so on, as it might occupy the PC's" hardware capacity.
- If the user needs to deliver the LAS files for the client, which shall be "intact", the Rearrange points and auxiliary file *.lasbxs option shall be used, as it will not modify the LAS header.