# filters.hag¶

The Height Above Ground (HAG) filter takes as input a point cloud with a Classification dimension, with ground points assigned the classification label of 2 (per LAS specification). It returns a point cloud with a new dimension HeightAboveGround that contains the normalized height value.

The HAG filter works by iterating through all non-ground points, finding the nearest neighbor (in XY only) amongst the ground points, and computing the distance between the two Z values.

## Example¶

{
"pipeline":[
"input.las",
{
"type":"filters.hag"
},
{
"type":"filters.ferry",
"dimensions":"HeightAboveGround = Z",
},
{
"type":"writers.las",
"filename":"output.las"
}
]
}


None