Comparing Global DEM with Lidar
This is currently replaced with
DEMIX wine contest. Lidar may be incorporated there "soon"
Compare Point clouds to global 1" DEMs (and potentially 3" DEMs). This documentation is not completely up to date
- Get
Key Global Regional DEMs.
This is geared to work with SRTM, NASA, ALOS, ASTER, and COP[ernicus] 1"
data
- Index in c:\mapdata\indexed_data\dems\ with
series names that are less than 6 characters (these will be used for
database field names and need space for the Z or SLP)
- Lidar or ICESat-2 photon data point cloud
- Input data
-
LIDAR Point clouds Open LAS file on DEM
- Create a point density map for the LAS file at 1" spacing (or other
spacing of the DEM), name
it "point_density.dem" and put in the same directory as the DEM
- Pick the Slice option on the
LIDAR Point clouds
- For ICEsat-2, Set options (which beams to use, the
minimum confidence for the point to use it, but you might already have limited
the confidence values that were exported).
- Pick
Canopy
button option on Slice window control form
- Requires SRTM, ASTER, and ALOS DEMs
- The program can automatically open them and gets the elevations
where needed
- Analysis of the point cloud data
- Filter to remove very large CLOUD_HT, or very high values of FR_SRTM or other
DEM
- Double click in a record
- You must still have the point cloud open
- Select database with results of the
Canopy button
- Filter to remove very large CLOUD_HT or large FR_xxxxDEM values
- Double click on one of the records
- Analysis of the comparision statistics with the results of the
Canopy button
in a DBF file, Lidar or ICESat-2 photon or elevation data data.
For ICESat-2 you might want to filter on date, beam, and track_id.
- Stats, Lidar to analyze global DEMs
- DEMs within point cloud range. Filter for one track, and one beam.
- Lat profile, current filter (generally the better choice
because of the orbital track geomtry)
- Long profile, current filter
- Distribution histograms (must be from a point cloud)
- Dirt and air shots: makes a
diagram with the over, under, within for the point cloud (or
ground/canopy top) for all points in the DB and each of the 3 global
DEMs, and a table with the results
- ICESat-2 beam splitter: makes a LAT profile and a
distribution summary for the
current filter, adding each of the 6 beams to the current filter
- Cloud summaries
ICESat2 anomalies:
- In Gabon, there are a number of geoid elevations below sea level.
These appear to occur where the canopy estimates exceed 100 m.
Open point cloud
- From Icesat-2 to LAS.
- From airborne lidar, which will have much larger point densities.
Canopy button results
Last revised 1/5/2021