Reclassify points in a LAS file using laspy

Question

I am trying to change the classification of all points in my las file above a certain height (z value) from 2 (ground) to 1 (unclassified). I wrote the following code to do this:

las = laspy.read("filtered plots/plot_37.las")
height_threshold = 333  # Replace with your desired Z value threshold

# Loop through the points, check their classification and height, and modify as needed
for point in las:
    if point.classification == 2 and point.z > height_threshold:
        point.classification = 1
        
las.write('plot_37.las')

However, upon reaching the line "point.classification = 1", I get the following error:

TypeError: object of type 'int' has no len()

I do not understand why the code is trying to check length instead of simply reassigning the value of the classification field. How can I find a solution?

Answer 1

You need to use the numpy index syntax to this, not a loop :

import laspy
las = laspy.read("filtered plots/plot_37.las") 
height_threshold = 333

# Classification set to "1" if the Z coord > height_threshold and classification = 2
las.classification[(las.z > height_threshold) & (las.classification == 2)] = 1

las.write('plot_37.las')