# Visualizing acquisition density¶

This exercise uses PDAL to generate a density surface. You can use this surface to summarize acquisition quality.

## Exercise¶

PDAL provides an application to compute a vector field of hexagons computed with filters.hexbin. It is a kind of simple interpolation, which we will use for visualization in QGIS.

### Command¶

Invoke the following command, substituting accordingly, in your OSGeo4W Shell:

 1 2 3 4 pdal density ^ c:/Users/hobu/PDAL/exercises/analysis/density/uncompahgre.laz ^ -o c:/Users/hobu/PDAL/exercises/analysis/density/density.sqlite ^ -f SQLite 

### Visualization¶

The command uses GDAL to output a SQLite file containing hexagon polygons. We will now use QGIS to visualize them.

2. Navigate to the output directory

3. Add the density.sqlite file to the view

4. Right click on the density.sqlite layer in the Layers panel and then choose Properties.

5. Pick the Graduated drop down

6. Choose the Count column to visualize

7. Choose the Classify button to add intervals

8. Adjust the visualization as desired

## Notes¶

1. You can control how the density hexagon surface is created by using the options in filters.hexbin.

The following settings will use a hexagon edge size of 24 units.

--filters.hexbin.edge_size=24

2. You can generate a contiguous boundary using PDAL’s tindex.