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The article makes it sound as though the seafloor is virtually unknown outside of areas surveyed with multibeam sonar, which is a relatively small fraction of t

by jjr8 9y ago

The article makes it sound as though the seafloor is virtually unknown outside of areas surveyed with multibeam sonar, which is a relatively small fraction of the seafloor. In fact, other technologies have been used to map the entire planet to a resolution of 15-60 arc second resolution (roughly 500-2000m). See http://topex.ucsd.edu/WWW_html/srtm30_plus.html http://topex.ucsd.edu/WWW_html/srtm30_plus.html for one such widely used, freely available dataset. What multibeam provides over extant dataset such as that one is much higher resolution.

mmanfrin 9y ago
roughly 500-2000m That gives broad strokes but I really would hesitate to use this as a counterexample against the notion that we haven't mapped the seafloor.
- jjr8 9y ago
  It depends on what you're interested in. Admittedly, if you want, say, a global map of all hydrothermal vents, 500-2000m is not going to cut it. But the time and cost required to map the entire ocean with multibeam sonar is huge, on the order of 120 ship-years for the deep oceans and 750 ship-years for the shallow (<500m) continental margins [1]. Global coverage at 500-2000m resolution from satellite gravitometers represents a very cost effective middle ground between that huge effort and what is currently available, which is a patchwork of soundings that has gaps 10s to 100s of km thoughout much of the ocean. (See Fig 2 of [1]). [1] Becker at al. (2009) http://topex.ucsd.edu/sandwell/publications/124_MG_Becker.pdf http://topex.ucsd.edu/sandwell/publications/124_MG_Becker.pd...
  - cobbzilla 9y ago
    could 100 solar/wave-powered drones do the job in 10 years?
rosser 9y ago
At that resolution, you probably couldn't distinguish the TransAmerica Pyramid from the SalesForce Tower. I wouldn't call that particularly well-known.
- icantdrive55 9y ago
  Fun fact: My dad worked on the TransAmerica Pyramid as an electrician. He once took me to work. I was always asking him about the very top. That day, he took me to the top. He opened a steel door, and set up a 6' wooden ladder. He climbed up the ladder, and there was a 1' x 1' square that you could fit your head through. He stuck his head through, and said it wasn't that great. I knew he was playing it down, for my sake. I asked him one more time if I could climb up and look. He climbed down, picked me up, and he climbed the ladder, and put my head through the hole. The hole was unfinished, and it was dirty inside the space. I remember seeing a gum wrapper, and that fine construction dirt up there. Looking back it was probably Sheetrock dust. I vaguely remember I could see the city, but the glass, or plexiglass, was dirty. It was neat though. The kids at school didn't believe me. He didn't want me to climb in, but I asked. The best part of that day was being with my dad. We ate lunch, and my dad said, 'Well at least your mom took the wrapper off the cheese today.' (This was the late 60's, or 70's, and my mom hated being a homemaker.)
  - jeff_tyrrill 9y ago
    icantdrive55, you've been shadowbanned for a long time, and I see no obvious reason for it in your comment history. I'd suggest getting in touch with the site admins to inquire.
    - mercer 9y ago
      Indeed. I have them tagged as 'shitposter' (with the HN Enhancement Suite Chrome extension), but I just had a look and I'm not even sure why I felt that tag was justified. At worst there's a lot of 'low-quality' rambling, but usually I then tag the user as 'shitty poster' (my approach to categorization can be a bit odd) and I'll downvote the worst of the comments when I see them. Could it be that after a certain number of heavily downvoted comments it causes an automatic shadowban? Or maybe some deleted or edited comments that were reason to do so?
      - consz 9y ago
nine_k 9y ago
At a resolution like that, a major city would be 20-50 pixels across. It's likely great for tracking large geological features, but still must miss a lot of interesting and important things.
- deleted 9y ago
  [deleted]
- jpttsn 9y ago
  Maybe we can let the prior assumption, that there are more geological features than cities on the seabed, do some work?

by jjr8 9y ago

mmanfrin 9y ago

roughly 500-2000m That gives broad strokes but I really would hesitate to use this as a counterexample against the notion that we haven't mapped the seafloor.

jjr8 9y ago
It depends on what you're interested in. Admittedly, if you want, say, a global map of all hydrothermal vents, 500-2000m is not going to cut it. But the time and cost required to map the entire ocean with multibeam sonar is huge, on the order of 120 ship-years for the deep oceans and 750 ship-years for the shallow (<500m) continental margins [1]. Global coverage at 500-2000m resolution from satellite gravitometers represents a very cost effective middle ground between that huge effort and what is currently available, which is a patchwork of soundings that has gaps 10s to 100s of km thoughout much of the ocean. (See Fig 2 of [1]). [1] Becker at al. (2009) http://topex.ucsd.edu/sandwell/publications/124_MG_Becker.pdf http://topex.ucsd.edu/sandwell/publications/124_MG_Becker.pd...
- cobbzilla 9y ago
  could 100 solar/wave-powered drones do the job in 10 years?

rosser 9y ago

At that resolution, you probably couldn't distinguish the TransAmerica Pyramid from the SalesForce Tower. I wouldn't call that particularly well-known.

icantdrive55 9y ago
Fun fact: My dad worked on the TransAmerica Pyramid as an electrician. He once took me to work. I was always asking him about the very top. That day, he took me to the top. He opened a steel door, and set up a 6' wooden ladder. He climbed up the ladder, and there was a 1' x 1' square that you could fit your head through. He stuck his head through, and said it wasn't that great. I knew he was playing it down, for my sake. I asked him one more time if I could climb up and look. He climbed down, picked me up, and he climbed the ladder, and put my head through the hole. The hole was unfinished, and it was dirty inside the space. I remember seeing a gum wrapper, and that fine construction dirt up there. Looking back it was probably Sheetrock dust. I vaguely remember I could see the city, but the glass, or plexiglass, was dirty. It was neat though. The kids at school didn't believe me. He didn't want me to climb in, but I asked. The best part of that day was being with my dad. We ate lunch, and my dad said, 'Well at least your mom took the wrapper off the cheese today.' (This was the late 60's, or 70's, and my mom hated being a homemaker.)
- jeff_tyrrill 9y ago
  icantdrive55, you've been shadowbanned for a long time, and I see no obvious reason for it in your comment history. I'd suggest getting in touch with the site admins to inquire.
  - mercer 9y ago
    Indeed. I have them tagged as 'shitposter' (with the HN Enhancement Suite Chrome extension), but I just had a look and I'm not even sure why I felt that tag was justified. At worst there's a lot of 'low-quality' rambling, but usually I then tag the user as 'shitty poster' (my approach to categorization can be a bit odd) and I'll downvote the worst of the comments when I see them. Could it be that after a certain number of heavily downvoted comments it causes an automatic shadowban? Or maybe some deleted or edited comments that were reason to do so?
    - consz 9y ago

nine_k 9y ago

At a resolution like that, a major city would be 20-50 pixels across. It's likely great for tracking large geological features, but still must miss a lot of interesting and important things.

deleted 9y ago
[deleted]
jpttsn 9y ago
Maybe we can let the prior assumption, that there are more geological features than cities on the seabed, do some work?