5 replies to this topic

[doolsduck]

I was chasing Lola crater depth data. Macpurity was kind enough to tell me about contours in Arizona state quickmaps which was quite helpful but a little tricky. I remember seeing a thread with an image of a graph of depth of a crater which I *thought* was plotted Lola data. I found it In a search so don’t know if it was a new or old thread but I can’t find it now. I wonder if it might have been from the Lunar Virtual Atlas. Can you do it in that? Or how would you find Lola depths? There are so many conflicting measurements floating around out there. So I’m looking for definitive data. Of course then one has to know if it is max depth from rim, depth from averaged rim or depth from the local area. It’s enough to make your head spin
Thank you

Edited by doolsduck, 10 February 2025 - 03:12 AM.

[david_od]

Indeed, Virtual Moon Atlas allows plotting height profiles.

You need 166 GB of space for storing the digital elevation models at maximum resolution (128 GB of those are from files at "1024 pixel/degree, resolution of 29 meters").

Since they need to be stored in a specific folder, I have them hard-linked there to their actual location in a different, more spacious drive.

Files are linked here: https://ap-i.net/avl/en/download

 

According to what I've found, it seems these data products are altitudes relative to a lunar reference radius of 1737.4 km. From the documentation of related, similar products:

Elevations were computed by subtracting the lunar reference radius of 1737.4 km from the surface radius measurements (LRO Project and LGCWG, 2008; Archinal et al., 2011). Thus elevation values are the distance above or below the reference sphere. The average accuracy of each point after crossover correction is better than 20 meters in horizontal position and ~1 meter in radius (Mazarico et al., 2012). The measurements were converted into a DEM (Neumann et al., 2011) using Generic Mapping Tools software (Wessel & Smith, 2008), with a resolution of 256 pixels per degree. In projection, the pixels are 118 meters in size at the equator. Gaps between tracks of 1-2 km are common, and some gaps of up to 4 km occur near the equator. DEM points located in these gaps in LOLA data were filled by interpolation Smith et al., 2010).

 

Attached Thumbnails

• 

Edited by david_od, 10 February 2025 - 05:05 AM.

[doolsduck]

Thanks David, that image looks very familiar...  So would we say the depth of that crater is 2231m plus/minus given that 0m is the reference sphere?

Cheers

[david_od]

What we can say for sure is that across the line I drew over the crater, the minimum depth is that quantity you cited. It's possible that another profile path might yield a deeper point within the crater, relative to the reference lunar radius.

[doolsduck]

What we can say for sure is that across the line I drew over the crater, the minimum depth is that quantity you cited. It's possible that another profile path might yield a deeper point within the crater, relative to the reference lunar radius.

Thanks David.  Macpurity showed me how to get these profiles in Quickmaps at  Arizona State and terrain height there seems to be referenced in the same way.  I hadn't thought about it before, but crater depth measured from the rim does seem to be the most relatable measure of depth, as if you were there standing on the rim.  For example Horrocks crater is more like ~2900m deep from that perspective.  Plato for example which comes up at a terrain height on the floor of ~ -2500m is more like 1500m-1900m deep depending on what part of the rim you're standing on. (I had no idea that the Mare were so far below the reference Lunar radius!

 

Cheers

[david_od]

Thanks David.  Macpurity showed me how to get these profiles in Quickmaps at  Arizona State and terrain height there seems to be referenced in the same way.  I hadn't thought about it before, but crater depth measured from the rim does seem to be the most relatable measure of depth, as if you were there standing on the rim.  For example Horrocks crater is more like ~2900m deep from that perspective.  Plato for example which comes up at a terrain height on the floor of ~ -2500m is more like 1500m-1900m deep depending on what part of the rim you're standing on. (I had no idea that the Mare were so far below the reference Lunar radius!

 

Cheers

Yes, I agree that's a more relatable reference. I hadn't thought of how deep Plato was, that's a lot!