The Live View Scan Angle Tab

*Live View is available in all license levels of LP360.

The Scan Angle settings allow you to filter data based on Scan Angle. These settings do not allow the assignment of color bands since LP360 does not have a specific “display by scan angle” viewing mode.

Scan Angle is associated with airborne and mobile laser scanning systems. It is the angle the laser pulse was emitted with respect to a reference coordinate system. For example, in an airborne laser scanner, 0 is nadir, negative scan angles are to the left of nadir viewing in the in-track flight direction and positive angles are to the right of nadir.

Overview of the Live View Scan Angle Tab

Scan Angle Row Columns

The Scan Angle table is shown above. The columns of the table (from left to right) are:

• Check box – toggle display of this range on (checked) or off (unchecked)
• Name – An arbitrary user defined name. This can be any alphanumeric text string you desire. It is optional
• Min – the minimum scan angle for this filter band
• Max – the maximum scan angle for this filter band

Adding Rows

There are three ways to add filter rows to the Scan Angle tab. These are listed the table below:

Manually Add/Edit Row

Pressing the Add Row button with no current rows selected invokes the Scan Angle Dialog.

The fields of this dialog are:

• Name – This field allows you to name the range for easy reference. For example, you could name the range “Low Areas.”
• Range Options:
  • Below – This will set a range from the minimum (e.g. -90 degrees) to the value you key in. The Min value in the resultant row will read “Min”
  • Above – This will set range from the value you key in to the maximum scan angle. The Max value in the row will read “Max.”
  • Between – Allows you to key in both the minimum and maximum scan angle values for this row. Note that you can key in “Min” (case insensitive so min, mIn, miN etc. are all equivalent) for the low value and/or “Max” for the high value.
  • [ ] Clip – This is disabled for direct key-in (it is used for data sampling)

You can press the Apply value to see the effect of the current settings without dismissing this dialog.

Adding a Row by Sampling

Pressing the eyedropper tool allows you to add a row by sampling the Map View.  When you press the eyedropper tool, the cursor will change to a cross symbol while it is over the map view.  Digitize a polygon around the area that you wish to sample.  Note that only points that are currently being displayed will be sampled (“what you see is what you get”).  The polygon is digitized by left-clicking each intermediate vertex and then double-clicking the final vertex.  Note that if you sample a large area, the system can take some time to display the Symbology dialog.

Note that when sampling for Scan Angle, you may want to set the display to Point Source ID and turn off all but the scan line in which you are interested. 

After sampling, you will be presented with the Symbology dialog discussed in the previous section but this time with the “Between” fields populated.  For example, in the example below, the sampled point scan angle ranged from 12.734 to 14.796 (the units are degrees).

You can future restrict this range by a standard deviation-based clipping value.  The default is 1 standard deviation (1 “sigma”).  This tends to reduce the impact of outliners.  Uncheck the Clip box if you do not want clipping applied or change the multiplier if you want something other than the default of 1.0.  For example, you can impose a less narrow clipping by using a value such as 1.5 as the standard deviation multiplier.  As you apply various clipping values, you will see the range value change. 

An example of sampling both edges of a flight line to clip out the center section is shown below.

Setting Multiple Range Bands

The multiple range band tool () allows you to create a user defined number of equally spaced range bands.  Pressing this tool presents the auto-range dialog.

The definitions of the values are:

• Start Value – The low value of the first band
• Increment by – The height of each band
• Number of bands – The number of rows you wish to create

The result of creating the 12 bands defined above is shown below with some bands off to show the effect.  Note that the View is in display by Point Source ID mode (e.g. flight lines for LIDAR data).

Edit Tools

Two tools are included for editing and deleting rows. 

Note that you can also edit a row by double-clicking on the desired row.