The Live View Intensity Tab

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

The Intensity tab contains settings that allow you to manipulate View displays based on the point Intensity field. 

Intensity in LP360

Intensity for LIDAR data can be thought of as the brightness of the laser return (echo) seen by the LIDAR sensor.  Many factors affect this intensity, among them are:

• • Laser power

  • Reflectance of the surface from which the pulse reflects

  • Flying height of the sensor

  • Divergence angle of the beam

  • Sensitivity and resolution of the detector

  • Angle of incidence of the laser pulse

  • Other factors

In SfM data, the intensity field is usual populated from the Red-Green-Blue image fields using a formula such as:

I = 0.59*Green + 0.30*Red + 0.11*Blue

For SfM software (such as Pix4D) that does not populate the Intensity field, you can apply the LP360 “Intensity from RGB” Point Cloud Task (PCT).

LP360 contains two modes of display that use Intensity.  The first is a View display mode that renders the view using the Intensity field. 

The second mode allows you to modulate other display modes by Intensity.  For example (Figure 33), if you are displaying by Classification, pressing the “Apply Intensity Shading” will blend the Intensity values into the Classification colors (also referred to as “modulating by Intensity”).  This allows features to be seen in the data while viewing in other than Intensity mode. See below: Left - with Intensity on, Right - without Intensity on.

The Intensity Tab

The Intensity tab of Live View is shown below.  This control allows you to do two different actions (which can be combined):

• Turn points on or off based on their Intensity value
• Colorize bands of intensity to a user defined solid color

Overview of the Live View Intensity Tab

Adding Rows

There are three ways to add filter rows to the Intensity tab.

Manually Add/Edit a Row

Pressing the Add Row button with no current rows selected invokes the Intensity Range 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 “Road Surfaces.”
  • • Range Options:
    • Below – This will set a range from the minimum (zero) 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 intensity.  The Max value in the row will read “Max.”
    • Between – Allows you to key in both the minimum and maximum intensity 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)
• 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 grey scale expected for Intensity.
  • 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 Intensity 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. 

Adding a Row by Sampling

Pressing the eyedropper tool allows you to add a row by sampling the Map View or Profile window.  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.

After sampling, you will be presented with the Symbology dialog with the “Between” fields populated.  For example, below the sampled point intensity ranged from 4 to 13.

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 a road, using a 1.0 sigma clipping and setting the Symbology to display this band as Red is shown below.  Note that intensity is not a very good object classifier so do not expect too much from this visualization mode!

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 definition of the values are:

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

The result of creating the 20 bands defined in above is shown below.

Intensity Symbology

The Symbology tool allows you to set symbology functions for the Intensity display.  Pressing the Symbology button invokes the Intensity Symbology dialog. 

Intensity currently is restricted to a single size for all intensity ranges being displayed.  The Point Size setting on the Symbology dialog is the size that points will be displayed with Legend is selected for the Point Size setting on the main Intensity tab of Live View. 

The default symbology for Intensity (if you have not added color bands that have been set to a solid color) is a color ramp.  The most common (and default) symbology is a grey scale ramp from black for the lowest values of intensity to white for the highest values.  The ramp is automatically scaled to the range of intensities in the current view. 

There is also available a color ramp.  This will map the intensities to the color bar. 

You can invert either ramp by checking the Invert button.  For example, if you invert the grey scale ramp, white will map to the lowest intensity and black to the highest.  This can sometimes be useful when looking in dark areas of an intensity image.

Per Row Symbology

You can select either “ramp” or a solid color on a per row basis for intensity.  For example, four intensity bands have been created in the example below.  Each band is currently set to map to a solid color.  You can toggle a band between a solid color and a ramp mapping by single clicking the color box of the row.

Toggle a row is depicted below.  In this example, points with intensities between 0 and 10 will be colorized by mapping to the grey scale ramp whereas the other three defined bands will be colorized according to their mapped solid colors.  Intensities outside of the defined bands will not be displayed unless the filter setting is set to “Superimpose”.

Filter Modes

Intensity filters allow a superimposition mode.  This mode is set via the Filter setting radio button option on the left side of the dialog.

The function of these settings are:

• Off – Ignore the filter.  This option is useful when you want to see the overall effect of your filter but you do not want to modify any of the row on/off toggles.
• Superimpose – The entire data set (that is not being blocked by some other Live View filter) is mapped to the currently selected Ramp (e.g. grey scale).  The defined ranges in the rows are then superimposed over these data.  IF a row is turned off (unchecked), the points in that row’s range will be mapped to the currently selected ramp.  If the row is on, that row’s selected color will be mapping on top of the current intensity display.  Obviously a row must be set to a solid color to observe this effect.  In the example of Figure 45, the second row of the table is superimposed over the normal ramp display.  
• Filter Only – This mode allows only points mapped to rows in the table that are checked to be displayed (again, assuming they are not being blocked by the filters of any other tab of Live View).  The display mode will be ramp or color depending on the selection in the Color column.   The example of Figure 46 allows only the second row to be displayed (Intensity ranges from 10 to 20 inclusive) and mapped to magenta. 

Left - Superimposed, Right - Filter only

Display Order

Points are displayed in the following order:

• No Filter – Not applicable
• Superimpose – Points that are not in the table are first displayed.  Rows of the table are then displayed from bottom row to top row.  For example, if row three and row two both contain ranges from 10 to 20, the color of the row in the upper position (in this example, row 2) will overwrite those of row 3.  This is why we do not worry about overlapping ranges when we create multiple range tables.
• Filter only – The rows are displayed with upper rows overwriting lower rows (assuming ranges overlap)