Data Preprocessing and Raw Data Inspection of LiDAR Data Processing Flow

After the LiDAR data is obtained, the data can be post-processed only after data preprocessing. After the data preprocessing, there is a data checking software to conduct a preliminary check on the data results. The general data format check has the following steps:

1. Format field check:

The submission of digital elevation data is in the format of an ASCⅡ plain text file. First, determine whether the data fields are consistent. For example, for a LiDAR data group, there are four columns for E, N, H, and Intensity. Check the number of fields, whether it is four columns, and finally print the report.

2. Coordinate statistics, check the reasonableness of the survey area

E, N, H (that is, X, Y, Z) coordinate statistics of coordinate data, including maximum, minimum, median, average, number of measurement points, etc., evaluate the rationality of the coordinates, and print the wrong report .

3. Data repetitive check

When the combined flight belt data becomes the survey area data, sometimes the flight belt data is read in repeatedly, resulting in duplication of the survey point data.

4. Whether the visual analysis has large errors in elevation data

Check the overlap data of the flight belts by means of the elevation profile drawn by visual analysis, check whether there is an elevation offset on the slope, and the left and right flight belts do not match. Secondly, visual analysis can also make terrain relief maps to visually analyze terrain.

5. Check the distribution and quality of the image, if it is a 12 bit image, it needs to be converted to 8 bit data;

6. Check the distribution of control points

Preprocessed data results

1. Track file (gps, ins information)

2. Video file (tiff or ecw format), video timetable file *.001

3. Analysis report (including whether there are errors, omissions and flight time)

4. Laser point (las format or text format)

5. The basic situation of LiDAR equipment (instrument model, various indicators, etc.)

6. Camera calibration file, including the camera's initial position, image frame size, distortion correction, etc. Generally use the camera file from the previous flight.