Create Grid from Point Clouds
Tab on LIDAR point cloud analysis form.
Creates a new
grid or grids that matches the DEM covering the map. Some
options require you to have or create a DTM.
Grid size (m)
Auto fill holes: remove small voids
Force UTM zone: if no zone is set, it will use the zone of the
currernt map. You should only change if you want to use an
adjacent UTM to match other data.
Word densities: by default these will be stored in bytes (max 255);
set this if you need up to 65K points.
- Ceiling + floor grids:
this will have the highest and lower return height in
the the pixel. This only works well if there are
multiple returns for every cell. If you create
them both at the same time, it will be much faster than
creating both sequentially.
- Distance Above/Below DEM: height in m for any points in the point
cloud that lie above or below the DEM. The DEM should be a
DTM. Uses zcrit on the Tools tab, and the DEM Z choice.
- Mean/Std: the mean height above the DTM and standard
deviation for all returns in the pixel
- DTM from ground classified points: this uses only the points
classified as ground, so its quality depends on the
- Low ground points x-y-z: this creates a database
with the X,Y, and Z coordinates of the lowest point
within the grid box that has been classified as ground.
This is intended to use as input for triangulation
creation of a DTM, with a reduced resolution to better
capture the local relief and not every small deviation
which might be better viewed as noise.
- Low points x-y-z: Same as the previous option, but
no prior need for classification. It will include
buildings, if the area has any.
- Point count:
- By Class: counts in each pixel for 5 classifications; depends on
the quality of the classification.
- Air points above DTM: these are from vegetation, power lines
or something else above the ground (the final return in
the pulse). Number of points above the DTM + Zcrit. This will be a minimum estimate, since
a pulse with a single return might not have reached the
- Non last return from LAS record:
record has the return number, and the
total number of returns from the pulse,
so if these are not equal, it is an air
- Ground points above DTM. Number of points within Zcrit of the
- First: first return from the LAS record
- Second return: this shows the distribution of pulses with
mutliple returns, positioned at the location of the second return.
The first and following returns could be at a different grid
location, depending on the grid spacing and the scan angle of the
- Single: pulses with a single return. These
will be in non-vegetated areas.
Fusion DTM from TIN
- Creates a DTM to cover the current map area.
- Three steps:
- Create single temporary LAS file , with all points on the
current map, with the current filter to select the points to
- fusion\dtm2tif to create a TIFF from the native fusion DEM
- GDAL_translateUTM to put the projection into the TIFF, which
only has a world file
Filter the LAS data first by classification code (Stats tab, Split by class) if the data has a good
||Points density, building category only. Zero values removed by
marking as missing. The colored pixels show points per square
meter, classified in the LAS data. This category generally appears to
be fairly accurate. Almost all points will be on roofs.
||Points density, medium vegetation category only. Zero values
removed by marking as missing. The colored pixels show points
per square meter, classified in the LAS data. This category
appears to be fairly accurate for the high density points, but a number
of the lowest density points are actually buildings.
Last revision 2/5/2018