Number of Points does not equal Total Points by Return

When loading data into LP360 a warning icon may appear in place of the expected green check mark indicating a valid LAS file. Files which have a warning state may still be loaded into LP360, but the software is making the user aware that a problem was found with the file. A common example of this warning occurs when the header of a file indicates that the file is not LAS compliant. For example, this may occur when the Number of Point Records does not equal the Sum Total of all Points by Return.

Warning message adding LIDAR data to LP360

Warning message adding LIDAR data to LP360

This is actually a very important warning message with respect to data delivery to the customer and it pertains to the number of returns that can be stored in the LAS file header.

A LAS file of versions 1.0 through 1.3, inclusive, supports up to 5 returns (‘echoes’).  While up to seven returns could theoretically be marked in the individual point records, this is not a proper LAS format. To encode more than 5 returns per pulse requires LAS 1.4, Point Data Record Format 6 and above.

It is most likely that a LAS file below version 1.4, PDRF 6-10 that contains returns marked above 5 would be rejected by the ultimate recipient of the  data (for example, USGS).

We see three possibilities for this data:

  • Have the data redelivered to you in a correct LAS format (most preferable solution)
  • Convert the data to LAS 1.4, PDRF 6 using LP360
  • Contact the ultimate customer and ask if they are willing to accept data in this invalid LAS format (most software will not correctly manage the points tagged as 6 and 7).  If the customer is willing to accept these invalid files, contact us again to discuss how you would like to manage processing of the points tagged 6 and 7.

GeoCue Group Support has written 896 articles

Leave a Reply