Hello,

 

I'm interested in the roughness of the Moon and am currently using the "LRO-L-LOLA-4-GDR-V1.0", "LDRM_16" surface roughness data. I have read the attached .lbl files describing the data however I'm still a little confused as to how the roughness is measured. Please can someone give me a hand?

 

My understanding at the minute is that a plane defined by three points ( 3 of the 5 LOLA footprint spot pattern) is compared to the plane fitted to either 5 points (1 LOLA footprint), 10 (2 LOLA footprints) or 15 (3 LOLA footprints). The standard deviation of the three-point plane from the "overall" plane is then converted into a roughness measurement in metres.

 

I was wondering if my understanding is correct and if not, I'd really appreciate it if someone would be able to explain how the roughness measurement works.

 

The slope baseline is said to vary from 30-120m and I was wondering where these values came from and how they related to the roughness calculations. Are they the baselines of the respective planes?

 

Also, the roughness is given in metres, is this the vertical roughness (z-axis) or the number of metres (vertical?) deviation from the plane?

 

Thanks so much,

 

Sarah.

Sarah,

 

The LOLA team has provided additional resources for understanding and using the surface roughness and slope GDRs:

 

1) Rosenburg, M.A., Aharonson, O., Head, J. W., Kreslavsky, M.A., Mazarico, E., Neumann, G.A., Smith, D.E, Torrence, M.H., Zuber, M.T. (2011), Global Surface Slopes and Roughness of the Moon from the Lunar Orbiter Laser Altimeter, Journal of Geophysical Research, 116, E02001, doi: 10.1029/2010JE003716. (available at http://www.agu.org/pubs/crossref/2011/2010JE003716.shtml )

 

2) The LOLA team has included a set of “extra” products that include maps of the coefficients that indicate a measure of surface roughness at http://imbrium.mit.edu/EXTRAS/FRACTAL/. See the README_FRACTAL.TXT for a description of these extra products.

 

I hope these help you understand the data set.

 

Regards,

Susan Slavney

PDS Geosciences Node

Susan,

 

Thanks for the advice. I had already had a look at these resources but had not realised that the paper was so closely related to the actual LOLA data. I will have a closer look.

 

Thank you,

 

Sarah