[Back to Detailed Agenda]
|
| Chairs: Warren Cohen, John Kimball
|
Discussion Questions:
- What are the most compelling new measurement and analysis techniques for NASA to invest in on behalf of Terrestrial Ecology, Biodiversity, and Applied Sciences? Why? What questions will they answer?
- Should the individual, PI-led studies in RSS be better coordinated to maximize the knowledge return to NASA and the community? If so, how would this best be done?
- Do any results form this area feed into NASA's Applied Sciences program?
|
|
|
|
--- Please forward any additional comments to the relevant Program Manager at NASA Headquarters. ---
|
In Diane's presentation referenced above, this statement appears under mission studies for veg 3-D structure: "The combination of a profiling lidar and a P-band (or L-band?) SAR represents the most promising approach to meeting the requirements for accuracy and global coverage." While I think this may well be a promising possibility, and should continue to be explored, I do not believe there is anything in the literature which quantitatively—with performance specs—supports the claim that this approach is most promising. There are a host of technical questions about this approach which, to my knowledge, are as yet unanswered. Two sample questions: 1) There is a small but growing body of evidence which suggests that direct structure from lidar or InSAR may outperform SAR power (P or L band) for biomass determination. Why is SAR power then more promising than InSAR-derived structure? Possibly because single-sensor SAR may be cheaper? If we're working against the clock, it is probably true that since SAR is more mature it might be more space-ready (though the Germans will put up a dedicated X-band interferometer within the next few years). Is the clock one of the motives for the promise of SAR vs the more direct structural measurement of InSAR? My hearty apologies if "SAR" in the referenced statement was meant to include InSAR!! My parochial interests are obvious; I apologize for them too. 2) The spatial scales of lidar coverage (10's of meters, or perhaps hundreds if new approaches to wide-beam lidar are in the works?) are orders of magnitude different than those of SAR or InSAR (10's of km from space). Yet forests appear to change their 3-D characteristics on scales of 100's of meters—this is my observation from anecdotal experience only. How then will we extrapolate lidar's superior vertical resolution to the spatial scales of SAR or InSAR over many "correlation lengths" of most forests? A rigorous set of methods for using lidar + microwave (SAR or InSAR) remote sensing together for global 3-D structure does not exist, and we can't be certain of their ultimate vertical accuracy as a function of lateral distance from the lidar track. I think we all have the gut feeling that the lidar-microwave combo is a winner, but I simply want to suggest caution about expressing its promise over other approaches in the absence of quantitative understanding (to my knowledge, once again) as to how we might rigorously combine them. I'd also like to suggest that, while not apparently part of the community's gut feeling, multi-angle MISR-type spectral methods for structure are being explored, and we might consider quantitative investigation of their potential in concert with the lidar-microwave combo.
– submitted by Robert Treuhaft at 2006-08-24 11:02:20 |
Does anybody remember MACs? We conducted several multisensor airborne campaigns(MAC)in the 1990's; these were "small" grassroots efforts proposed by teams of PI's to gather and analyze multiple airborne data sets over a common site or set of sites. None have been proposed in a long time. Would reviving them meet a current need?
– submitted by Diane Wickland at 2006-08-22 14:46:21 |
|
|
|
+ QUESTIONS? CONTACT US
|
