Since eucalyptus trees are planted very near to each other it is possible that some are not even hit once by a laser pulse because the scan lines can be up to 1.8 meters apart from each other. The overlap area of neighbouring strips helps in scaling down the data gaps.
Furthermore a combined use of first and last pulse data for all the calculations concerning vegetation was investigated. In general the last pulse data penetrates the vegetation to a certain extent and do not contain information on the vegetation surface. But if the vegetation has a very high density also last pulse data may supplement the DSM in areas with no data. To study the influence of the additional use of last pulse data all calculations at the plots were carried out once more with both first and last pulse data. A comparison of the final results did not show any differences what yields to the conclusion that the additional use of last pulse data for the detection of tree tops is not suggestive