Modify the Scan Angle Filter

Note: The following options only apply to LP360 2020.1 or newer.

The Live View Filter - Scan Angle tab settings allow the user to filter data based on Scan Angle, which is typically associated with airborne and mobile laser scanning systems. It is the angle that 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 tab table is shown below. 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:

The Live View Scan Angle Tab

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)

The Live View Elevation Tab

• Color – Color sets how you want this range displayed. There are two options
  • Color Ramp – Use the current color ramp that is set for this filter. This is set using the Symbology tool. It defaults to the typical color ramp expected for Elevations.
  • Solid Color – this selector allows you to display the band as a solid color rather than a color ramp. For example, if your range is 10-20 and you set this to solid color, red then all points with an Elevation value between 10 and 20 inclusive will display as red.

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

The Live View Scan Angle Tab

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.

The Live View Scan Angle Tab

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).

The Live View Scan Angle Tab

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.

Note: The following procedure applies only to LP360 v2019.1 and earlier.

The Scan Angle Property page allows you to customize settings for filtering points based on their Scan Angle values for display or for performing point cloud tasks, similar to a Class filter or Return value filter.

1. Open the Properties dialog box on the LP360 toolbar.
2. Click the Display tab, then click either the Points Filter or TIN Filter tab.
3. Click the Scan Angle tab.
4. On the Scan Angle property page, set one of the following options based on how you want the Scan Angle values to be filtered

Option 1: Include all Scan Angles (Default)

This option will include all points with scan angles to display or to process a point cloud task. Adding and removing points is not an option when including all scan angles.

Option 2: Filter Based on Scan Angles

This option allows you to enter the ranges of minimum and maximum Scan Angle values to display or to process a point cloud task. The Add button is used to enter minimum and maximum values, and you may enter more that one row of values. Please see the description of the descriptions of the Add, Edit, Remove, and Clear buttons and the minimum/maximum values guidelines below.

Add:

You must use the Add button to enter minimum and maximum Scan Angle values in new rows. Click Add for each new row you add.

Edit:
Clicking this button allows you to edit the values within a row from the adjacent list view.

Remove:
Removes a row from the adjacent list view. This means the minimum and maximum values in the row are removed from the Scan Angle Filter.

Clear:
Removes all rows from the adjacent list view. This results in a filter with no minimum and maximum values.

 

Additional Guidelines:

• You may use any valid integer as a minimum value.
• You may type "Min" (not case sensitive) to set the minimum value of all existing points.
• The minimum value should be less than maximum value (if a maximum value has already entered).
• You may use any valid integer as a maximum value.
• You may type "Max" (not case sensitive) to set the maximum value of all existing points.
• The maximum value should be greater than the minimum value.
• You may specify any number of minimum and maximum value pairs; i.e., there is no limit to the number of minimum/maximum value rows that you can have.