• LASPNT: Import of lidar data in LAS or LAZ format

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Presentation and options

This application allows to consult or import lidar data from files in LAS or LAZ format (compressed variant from the aforementioned format) to the MiraMon structured vector format of points PNT. Lidar data (light detection and ranging) are taken by remote sensing sensors that produce polarized light (normally from the region between UV and shortwave infrared [up to 1500 nm]) and detect the echo signal, as well as its intensity, and deduce the distance to the object of which the echo is detected. LAS format is a public format to interchange lidar data between providers and clients that is supported by ASPRS (American Society for Photogrammetry and Remote Sensing). This format, binary, is designed to data storage (point clouds) collected by lidar sensors boarded into aerial platforms (planes, or even drones). LAS format has information of XYZ coordinates on each return, its intensity, the incident angle, etc.

On a lidar file import, a PNT file is created with altimetric information and several DBF tables. The information is divided in more than one table with the aim that the main table could be lighter (with a smaller file size), and to contain the information most usually needed, leaving in other tables those less relevant information that, if necessary, could be linked through a dynamic join operation from the "Thematic information" tab of Universal Geospatial Metadata Manager, GeM+, or through a physical join operation from the MiraDades application (creating, in this case, a single table with all the information).

The main table of the PNT file includes the following information of each point: Z coordinate, intensity, classification (surface typology in the point according to the sensor processing software), scanning angle, number of the returned pulse, total number of returned pulses, scanning direction (+ if it is from left to right, or - if it is from right to left), if the point is close to the scanning limit and, on the case that there is standard GPS time information, date and time of the pulse (in UTC time).

A first auxiliary table is also generated [with the same name of the layer but adding the _XYIDT.dbf suffix] where the following information of each point is included: X and Y coordinates, user's ID, point's ID and, in case of having it, original time of the GPS (i.e., without turning it into standard time in date and time as is written in the main table).

In addition, in the case of having information about the RGB and/or near IR channels, a second auxiliary table will be created [with the same name of the layer but adding the _color.dbf suffix] with the values of these color bands for each point.

If some of the fields of any of the tables are wanted to be erased, it could be done with MiraDades (or with GestBD if an automatization in a BATCH process for several files is needed).

As it has been said, if it is desired to have the whole or a part of the auxiliary table information in the main table, a physical join could be done with MiraDades (or with GestBD if an automatization in a BATCH process for several files is needed). Also, a dynamic join could be generated through the Universal Geospatial Metadata Manager (GeM+).

The original GPS time can be standard or weekly GPS time. In case of being standard, it is needed to add 10⁹ to obtain the absolute GPS time. On the other hand, weekly GPS time is related to the number of seconds of the week counting from Sunday midnight and it does not allow to obtain the absolute GPS time because the number of weeks or days passed since the origin of absolute GPS time is unknown.

This application has two options:

Information: This application allows to obtain information about a lidar file

Import: This application allows to import lidar files (in LAS or LAZ format) into the MiraMon structured vector format of PNT (points).

Dialog box of the application

LASPNT dialog box