Hi all
I'm asking if we could be helped by someone so that we don't miss relevant research!
We are looking at the radiometry and geometry of repeated waveform LiDAR scans in vegetation such that non-scene-related aspects (sensor etc.) that influence the signals are minimized (by using same trajectories, same sensor, same sensor settings) so that signal changes would reflect the structural changes in the vegetation/trees over time.
Is anyone aware of relevant papers that deal with multi-temporal LiDAR (waveform or discrete), impact of vegetation phenology on LiDAR (radiometric) features?
I'm also willing to discuss the topic, if someone shares an interest.
Thanks, ilkka korpela
I am also quite new to it. We are currently trying to evaluate the lidar data from GEDI and UAS. and how it could be used in measurement of canopy structures
Comparing the signals directly seems a bad idea to me because differences in the point of view and changes on the shape of the trees due to wind will affect the signal too much. It is possible to derive some parameters for individual trees or for areas as tree height, aerial biomass, etc. for each epoch and then compare how these parameters evolve with time. The computation of these parameters on areas or for individual trees will smooth unwanted noise.
See for example Article Measuring the growth of individual trees using multi-tempora...
Antonio Ruiz thank you for replying. Our boreal trees change gradually over time as for example the conifers have 3-8 needle cohorts. And yes, we are using trees as targets of observations (and plot / cylinders where appropriate). By repeating the scans following exactly the same trajectories and by using the same sensor and sensor settings we have been able to minimize the effects (artifacts) due to say scan zenith angle and range which can greatly influence observatoins. We are mainly interested in geometric-radiometric features that may be usable in species classification - which of them correlate over time, which are "winter-specific" and which are "summer (leaf-on) specific", and how these species-specific features are influenced by phenology (winter, early summer, late summer). For example we are interested in how well the different features correlate over time, measuring some characteristic trait that remains unchanged in the tree, be it any time of the year. Phenologic effects on LiDAR waveform can be substantial (leaf-on, leaf-off) or subtle (conifers), and observing that subtle effects are there, requires very careful experimentation. Luckily we did not have wind. Only once in my career I have had an issue with wind as it made image matching to fail in slender birch trees. Thank you for the reference. ILKKA
Adedeji Oluwatola Hello, GEDI data must be fascinating! Never set my hands on that. Have done some peer-reviewing of papers in GEDI and other satellite LiDAR. I never stepped outside a LiDAR footprint of wider than 60 cm :)
And then you go for the other extreme, UAS. I'm envious at the latter opportunity. There are some commercial UAS operators in Finland (my country) and hope to be able play with UAS-borne LiDAR some day.
Monitoring applications are interesting and therefore time-series and multi-temporal data analyses interest me and I'm interested to know if radiometrically accurate repeated datasets have been analysed and reported somewhere.
ilkka
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