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Esri LAS Optimizer/Compressor
Updates
Revision 1.2.4:
- Fix: rare case where decompression/validation claims zLAS file is invalid when it's actually valid.
- Fix: carriage return sent to active window at end of process when EzLAS run from command line.
Revision 1.2.3:
- Added user specified temp path to which intermediate files will be written.
- Enable the 'Import PRJ file' option on the 64 bit verion of EzLAS when ArcGIS Pro is installed.
- Fix: crash when using the 'Import PRJ file' option when ArcGIS 10.4 and higher is installed.
Revision 1.2.2:
- Digitally signed executable.
Revision 1.2.1:
- Fix: when using the command line the process may 'validate' instead of compress due to an uninitialized variable for validate command line switch introduced in v1.2.
- Remove version number from the application's exe file name.
Revision 1.2:
- Support for LAS 1.4, all point record formats.
- Output zLAS files are backward compatible when LAS 1.3 or earlier payload is used.
- Retain original time stamp upon decompression if las file not altered in any way.
- Command line switch to verify integrity of zLAS files.
- Option to stop process when encountering error with a file.
- Drag and drop files/folders.
- Do not overwrite log file.
Revision 1.1:
- Added support for parallel decompression.
Overview
The Esri LAS Optimizer improves archiving, sharing, and use of LAS format lidar. Optimization is accomplished in several ways:
- Lossless compression
- Spatial indexing
- Statistics generation
- Efficient direct use without need for decompression
The compression ratio the optimizer can achieve is typically much better than generic compressors. This is because it’s targeted specifically for LAS. In addition to a high compression ratio, the compression is lossless so you needn’t worry about losing any information. On top of this, the compressed files are directly usable in ArcGIS via the LAS dataset. Just add the files, which are named using the extension *.zlas, to a LAS dataset, like regular LAS files, and you’re ready to go. No decompression is necessary. Because the data are also spatially indexed and have statistics they’re more efficiently accessed and easier to use than regular LAS.
Direct use of zLAS files containing LAS 1.0 to 1.3 payloads requires ArcGIS 10.2.1 or higher. Direct use of zLAS with LAS 1.4 payloads requires ArcGIS 10.3 or higher.
Requirements
- Windows 7 x32/x64 or higher.
- Some machines may require a Microsoft C++ Redistributable Package be installed if certain libraries used by the compressor are not already on the system. See the Notes section for more information.
- ArcGIS 10.1 or higher is needed only for using the option to import spatial reference information from an Esri PRJ file. Otherwise, ArcGIS is not needed.
Usage
This section covers the usage of the tool and its options.
entirely. It’s our experience at Esri that virtually all post processed (e.g., tiled, classified) LAS has already had the point order changed relative to the original scan order and changing the order again for the sake of accessing the data more efficiently is an improvement to the data. This is why the option is on by default. If the input data have already been rearranged (see ‘Notes’ below), the optimizer will recognize this and keep that order, saving itself some work.
Import PRJ file: this option is on by default and is used to replace or add spatial reference information from an Esri PRJ file, if one exists, into the corresponding compressed output. Unchecked, if a *.prj exists, it will only be copied next to the output, rather than being added into it. If checked, the output will have the PRJ information embedded into it and will not have a ‘sidecar’ prj file. The decompressed version of the LAS file will also have that information embedded in its header. For this reason, the decompressed LAS file will not be identical to the input. Considering a PRJ is present it would seem the change is for the better, it’s fixing a shortcoming of the original LAS, and is why the option is on by default.
Note this is the one option that requires an ArcGIS installation. It will be disabled if a compatible version of ArcGIS is not found on the system. By ‘compatible’ we mean that when using the 32-bit version of the optimizer you need a 32-bit version of ArcGIS (e.g., Desktop). For the 64-bit version, you need a 64-bit version of ArcGIS (e.g., server). We recommend running the 64-bit version of EzLAS. Only if you need the ‘Import PRJ file’ option and have a 32-bit version of ArcGIS should you use the 32-bit version of EzLAS.
Advanced options: there are three features available from this sub-dialog. System resource usage, file error handling, and temp file path.
System resource usage : enables you to control the amount of CPU resources that will be allocated for optimization/compression and decompression. It’s a relative amount offered in increments: 25%, 50%, 75%, and 100%. This percentage relates to the number of available logical processors that will be used in parallel. For example, on a quad core machine with 8 logical processors a value of 50% will spawn 4 threads. By default, the percentage is 100%, to use all computing resources. This is the recommended value and should only be changed if there’s a specific reason why all resources should not be allocated, such as if the application is being run in a server environment where one process should not be allowed to dominate the resources of the machine.
File error handling : with this turned on the process of compressing or decompressing multiple files will halt if an error occurs with any file. The default is off, to allow the process to continue working on the remaining files. Regardless of whether this option is on or off, all problems are always reported in the output log file.
Temp file path : this optional path is used to write scratch files when the rearrange point option is being used. Those scratch files can be large (depends on the size of the input LAS file(s)) so the ability to write them to a different, and potentially faster, drive than the target drive for the zLAS file output can improve I/O performance.
Output: here you specify an output folder. If it doesn’t already exist it will be created. Depending on the option you picked, either the compressed or decompressed files will be written to this location. You can choose to overwrite files if they already exist. Progress is reported on the dialog and an output log file, called EzLasLog.log, is written to the output folder. If the log already exists a unique name will be generated (e.g., EzLasLog (1).log).
Start, Pause, and Cancel
Pressing the start button will initiate the process. While processing the Start button turns into ‘Pause’ which can be used to temporarily halt the process. The Cancel button will terminate the process but leave the dialog up. To quit use the ‘x’ in the upper right hand corner of the dialog.
Command line
EzLAS supports command line use as well as a graphical user interface. The command line options are listed below. The command line help can also be returned by typing “EzLAS /?” in a console window.
EzLAS input output [/D] [/S] [/R] [/PS=[value]] [/P] [/C=[number]]
input Specifies the directory or LAS file name. output Specifies the output directory name. /O Indicates that the process can overwrite existing output files. /D Indicates that the process is for decompression. /V Indicates that the process is for verifying the integrity of zLAS files. /S Indicates that sub directories should be included. /R Indicates that the process should rearrange point records.
/PS= Specifies one of the three point spacing estimation options. PS=S (no space in between) indicates 'estimate by scanning file'. PS=H (no space in between) indicates 'estimate using header info'. PS=[number] indicates 'use the specified number' (example: PS=1.5).
/ES Indicates that the process should stop if a file error occurs.
/P Indicates that the process should replace LAS file's projection with Esri's Prj file if one exists.
/C= Specifies the CPU power to be used in percentage. Example: C=50 (no space in between) specifies 50% of the CPU power. Note that the input usage will be snapped up to one of the following four predefined values: 25, 50, 75, and 100. For example, input C=10 will be changed to C=25, and C=80 changed to C=100.
/Temp= Specifies the directory name for scratch files.
