Requirement specification for LiDAR data

LiDAR data is a complex data set that can take a long time to process, depending on the scope, design and need for possible edits. To facilitate the processing, you must use the LAS or LAZ format for LiDAR data sent to Lantmäteriet.

Below are some guidelines to keep in mind when compiling the LiDAR information before an application for a dissemination permit.

Share information about the dataset with us

In order to process the data set, we need the following information:

• Sensor model.
• Coordinate system, both in plane and in height.
• Trajectory files that provide information about the scanner’s position while capturing the point cloud.
• The software used to process the information.
• Acquisition of period

Point Data Record Format (PDRF)

The point data record format, and indirectly also the LAS version, should fit the dataset. That is:

• If your data has more than five returns/pulse, a point data record format that supports more than five returns should be used (point data record format > 5).
• If your data does not contain RGB information, do not use a point data record format customized for RGB information.

For more information about the point data record formats, see the document LAS Specification v.1.4 R14 (pdf, opens in new window).

Extra bytes

As far as possible, avoid using extra bytes in point data as this can cause problems when editing. Extra bytes is used to describe and store additional attributes for each LiDAR return.

If you need to use extra bytes in your data set, we need a detailed description of the information. What it describes, what it is used for and how it is designed. This is so that we can decide whether any editing affects the data set or not.

VLR/ExtendedVLR (Variable Length Record)

Make sure that there is relevant information in the VLRs to make it easier for us to process your data, such as information about coordinate systems, self-defined point classes and information that describes any extra bytes for each return.

Point sorting

In order to edit your data, it is important that returns belonging to the same pulse are placed next to each other in logical order in the point cloud.

The returns should be sorted according to:

1. GPS-time
2. Channel
3. Return number, ascending

File sizes and tileing

If individual files are too large, our systems might not be able to process the data.

If your uncompressed data (LAS) exceeds 2 GB/75 million returns per file, you should consider dividing the point cloud into smaller portions that are easier to work with, so-called tiles.

It is possible to merge multiple overlapping flight paths in the same file/tile, as long as the point clouds have unique Point Source ID's.

If you use the LasTile (opens in new window) program from the LasTools toolbox when tiling, we cannot guarantee that the "-reversible" function will work after we have processed the data. This is because returns in the returned dataset may have been deleted.

Classification

Submitting classified data does not cause any major problems for our processing, but if you use self-defined classes, be sure to describe these either by adding a Classification Lookup VLR or attaching the information in a separate file.

Trajectory files

For certain types of editing, we need trajectory files in TerraScan trj format (opens in new window). If we do not get access to these, there is a risk that your application for dissemination permit will be denied.

Other things that may be useful to know regarding edited LiDAR data

• The number of returns in the treated data may differ from the number of returns in the submitted data.
• Point data in the returned point cloud may not have the same index as the submitted data. This means that if you have external connections to specific point indexes, these may be broken.