Knowledge Base
B090901 - A note about lossless encoding in LiDAR Compressor
Summary:
We asked one of our customers to take an in-depth look at LizardTech™ LiDAR Compressor and subject it to some hard scrutiny. LiDAR Compressor is a new technology and a new product, and we wanted as many pairs of eyes on the end result as we could get.
Our customer pointed out that our GPSTime field for LAS files is not truly lossless. This is because that field is in “floating point” form rather than being a “quantized” value.
Floating point values must be quantized before mathematical operations such as compression can be performed on them (quantizing is a rounding operation that discards some number of the least significant bits of data). Most LAS data is delivered to users already quantized. A typical exception is GPSTime.
This changes how we can talk about lossless compression, and there’s no way around it. Floating point values simply cannot be losslessly compressed because they are infinite.
We apologize for any inconvenience this oversight has caused. What’s still true is that LiDAR Compressor can losslessly compress all quantized raw data present in a LAS file, which means that that data can be decoded back out to its original uncompressed form, bit for bit.
If you have any questions or concerns about lossless compression in LiDAR Compressor, please contact LizardTech Support at http://www.lizardtech.com/support/contact.php.
This article was last updated or verified on 4 August 2012.
