I am working with multi pulse LiDAR data that collects points along a number of lines within the flight path. From what it appears there are four scan lines within the data, at different intervals but with identical gps timestamps. I am trying to determine the name and number of individual lines within the las file. I am using libLAS module in Python.
I found this documentation that explains the different fields stored in an las file. It mentions a data field (get_data and set_data) at the very bottom of the page.
The 'point data format' and 'point data record length' in the header set aside space for this 'data' field. My header says I have 28 bytes set aside for the data field, and there are 28 values stored in the data field. The 19th value (at least in two datasets from two different sensors) refers to the line number. I have a single value in single pulse data and 4 in multi pulse data.
I was wondering if there is a standard for what is stored in this field or if it is proprietary.
Also, as a way to get the name of each scan line, I wrote the following code:
import liblas from liblas import file as lasfile # Get parameters las_file = r"E:\Testing\00101.las" f = lasfile.File(las_file, mode='r') line_list =  counter = 0 for p in f: line_num = p.data if line_num not in line_list: line_list.append(line_num) counter += 1 print line_list
It results with the following error:
Traceback (most recent call last): File "D:\Tools\Python_Scripts\point_info.py", line 46, in <module> line_num = p.data File "C:\Python27\ArcGIS10.1\lib\site-packages\liblas\point.py", line 560, in get_data length = self.header.data_record_length File "C:\Python27\ArcGIS10.1\lib\site-packages\liblas\point.py", line 546, in get_header return header.Header(handle=core.las.LASPoint_GetHeader(self.handle)) WindowsError: [Error -529697949] Windows Error 0xE06D7363
Does anyone know more about the line numbers stored in the las point/header? Can anyone explain the error?