The Delta Z Property page contains the settings used for customizing Delta Z (dZ) imagery display. Images produced by coloring LAS data by their elevation difference with respect to different point source IDs of the data (or different scanners for mobile data - see explanation of this option in step 7 below) are called Delta Z (dz) images or Color by Elevation Difference images. These images are used to visualize elevation differences between overlapping LIDAR flight lines and the mismatch between overlapping sources of LAS data. If there is no overlap of the LAS data in the pixel output, then the intensity of the LAS point that has highest elevation is set as the pixel value for Red, Green, and Blue bands.

Delta Z (dz) images are very useful for doing a quick assessment of the quality of the relative height match between overlapping strips. In a perfectly calibrated system with perfect GPS/INS data, we should never see a difference in height where strips overlap, because these points represent the same location on the ground.

Picture of the Delta Z Property Page

The Delta Z Property Page

How to Modify the Delta Z Legend Properties

 

1. Open the Properties dialog box by clicking the  button on the LP360 toolbar.

2. Click the Symbology tab, then click the Delta Z tab.

3. Under Cell Edge Length, enter a value greater than zero Map Units. 

4. Select the number of intervals (from 3 to 10) for the dz images in the Intervals list. Based on the number of intervals you set here, along with the interval size, the Range column in the table displayed below displays the elevation ranges and the Color column displays the color that will be used for the range next to it.

Note   To change the color associated with a particular range, double-click the color box in the Color column and select a different color in the color selection dialog.

5. Enter an Interval Size for the images. 

6. Select Absolute Values if you want to use the elevation difference between higher elevation and lower elevation of the LAS data in the output cell. If this option is not selected, the elevation difference of the highest point source ID and lowest point source ID is used as the elevation difference for the output cell. This elevation difference is used to color the pixels. 

7. Select Between Scanners Only if you are using mobile mapping LIDAR data. Mobile data has different scanners rather than different strips and point source IDs. This option displays the dz images for the mobile data using different scanners.

Note   For LAS 1.4 and above, the scanner number is obtained from the LAS point. For LAS 1.3 and below, the scanner number is obtained from its filename.

8. Click OK.