Changes between Version 45 and Version 46 of Processing/LidarCalibrationProcedure

Timestamp:

Oct 10, 2014, 11:01:12 AM (10 years ago)

Author:

lah

Comment:

--

Processing/LidarCalibrationProcedure

@@ -43 +43 @@
 1. Process the Navigation as per usual using IPAS Pro and Grafnav
 
-2. In ALS Post Processor:
+2. Attune can be used to retrieve initial roll, pitch and heading errors.  These will need to be manually tweaked using lag and alspp, so this step may be skipped.  If skipping, set-up alspp as below up to and including 'run compute scanner offsets', then skip to 6.  You will need to manually choose pitch, roll and heading offsets, which may initially be very far off.  Start by making large changes then reduce as the errors decrease until the data overlap.
+
+In ALS Post Processor:
  * Load up the calibrated reg file (received from Leica) to get correct scanner settings
    * This will be in /users/rsg/arsf/doc/leica/*year*/. If it isn't you should move it there and add it to svn.
@@ -131 +133 @@
 7. Now analyse the results in LAG or !TerraScan
  * Check profiles etc for misaligning flightlines.
- * To load all flightlines will probably need to use a fence (this is like a region of interest)
- * To check the Roll accuracy – check opposing flights and look at cross sections at either end of the swath for a tilt (across track).
- * To check the Pitch accuracy – check along track on slopes for offsets
- * To check the Heading accuracy – check the parallel lines for along-track offsets close to line edges
+ * To load all flightlines will probably need to use a fence (this is like a region of interest).
+ * To check the Roll accuracy – check opposing flights and look at cross sections at either end of the swath for a tilt (across track).  Different altitudes usually have different roll offsets; select one that is a compromise between the high and medium altitudes.
+ * To check the Pitch accuracy – check along track on slopes for offsets on opposing lines.
+ * To check the Heading accuracy – check the parallel lines for along-track offsets close to line edges. Don't worry about cross-track offsets at this point; they should be corrected later.
  * Also possible to check for errors by re-ordering points by elevation
 
@@ -165 +167 @@
      * Copy the GCP's to the 02a_ROff_+-7Deg folder. You may need to edit this file to remove some points. 
      * Run lascontrol.exe -i *.LAS -cp gcp_points.txt -parse xyz (you may need to edit the parse command depending on the format of the GCP's you are using e.g. -parse sxyz for 4 columns)
-     * Scan the output and remove any bad points from the gcp file and re-run
+     * Scan the output and remove any bad points (any z values that are significantly different)from the gcp file and re-run
      * Look at the average (abs) value, this is used for the nominal range offset A1. This value should not change dramatically from season to season
      * Note: if there are negative values in the lascontrol output then calculate the average value yourself (lascontrol gives the average absolute value)