This is because csc.noaa.gov lidar files are stored with the .laz
file format extension. It is a compressed version for .las
extension.
Read this* article to know more about compressed las files (.laz).
In order to correctly visualize these types of files, you need to retransform them from .laz
to .las
. Use the open-source LiDAR compressor LASzip to accomplish this task.
Here is one example:
Suppose that LASZip is installed under the drive C:
, and the .laz
file is stored under a fold named project
(C:\project
). Do the following:
c:\LASZip\laszip -i c:\project\aaa.laz -o c:\project\aaa.las
aaa
is just a name for the file which I have made up. Here is more some tips from Bruce Simonson about potentializing the use of LasZip .
*Reference
ISENBURG, M. LASzip: lossless compression of LiDAR data, 2012.
Examples
See below some examples about how .laz
files become disfigured in comparison with its uncompressed version .las.
:
This is the Fugro Viewer. While the dots in the .las
file are concentrated in the upper and lower layers in the z direction (left panel), the dots in the .laz
version are more homogeneously spread (right panel).
This is the Quick Terrain Reader. The dots in the .laz
file are flattened in the z direction (right panel).
There is no specific GIS software for doing this: most will handle the RGB image and the Lidar data.
Basically, NDVI is (NIR - RED)/(NIR + RED). Most of the time, aerial Lidar gives you the NIR value (to be checked in metadata) and the first band of your RGB image gives you the RED value. Just make sure that your data are calibrated to reflectance (or, if not possible, normalised in the same range of value -> this will give you a good discrimination, but no absolute threshold can then be used).
As a remark, Lidar does not always provide the intensity information. Sometimes only the distance information is available.
Best Answer
It is possible to visualize LiDAR data (as points) and corresponding RGB values within ArcScence (as long as the .las files contain such information, of course). See: Example use cases for displaying LAS datasets as points in 3D (emphasis mine):
Outside of ArcGIS there are other options (as you already mentioned). For example, FugroViewer and Fusion.
Alternatively, as suggested by Mapperz it is possible to convert a LiDAR point cloud to raster format and visualize it accordingly. To do so, use the LAS dataset To Raster tool and select the optional parameter
value_field
equal to RGB.But, be aware that when converting a point cloud to raster there will be some loss of information because pixels representing more than one point will have a unique RGB value.