Mapping Ground Zero with Lasers

securitas writes: "Amazing how the WTC disaster has shone a light on technology (pun intended). LIDAR (Light Detecting and Ranging) is the optical equivalent of RADAR. It's being used to create hyper-detailed maps of the WTC disaster site from an altitude of 5000 feet to detect shifts in the rubble as well as areas in danger of collapse."

Comments

Interesting

[fjordboy]

This is really cool, and I hope it helps the rescue effort a lot. One of my friends told me that they were implementing some form of sonar to test for structural stability and whatnot...does anyone know anything about that? I couldn't find it on any news page, so I think my friend might have been mistaken. I think this would probably work better than sonar, and I really hope it is helpful.

Re:Interesting

[GospelHead821]

I'm not sure about the specifics, but if you pulse a very low-intensity sound wave through any substance, you can measure the distortion of the wave to see whether the material is behaving as you expect it to. If it is not, it is often because of miscroscopic structural defects.

Re:Turbulence etc.

[stjobe]

Why does this require a LIDAR to do

It probably doesn't - most likely it's just to note that the LIDAR is pretty accurate - enough to pick out debris on the roofs of buildings.

LIDAR

[iota]

Just in case anyone is interested, LIDAR is actually what 'Laser radar guns' use to track your speed. So if someone ever tells you that they got pulled over because of a Laser gun, tell them it was LIDAR they should blame.

Try telling that to a cop... "No officer, its LIDAR! Really!"

jason

Re:how is this done?

[stjobe]

Quote the article:

"A week ago, with billows of gray smoke still pouring from the remnants of the World Trade Center, a twin-propeller plane flew 5,000 feet overhead, bouncing pulses of infrared laser light off the scarred terrain below."

So I guess they don't actually monitor it constantly.

Re:maybe offtopic

[budgenator]

not sure about any real attempt to dig it out, there's lots of problems there.
First the WTC was built in a "bathtub" because the foundation is below sea level so if the bathtub is cracked mud could rush in and de-stablize near by structures like subways, utility conduits and other building foundations. The WTC actualy re-inforced the tub internaly to prevent its colapse; now its rubble. To do this there is talk that they may have to drill through the tub and sink tie-backs into the bedrock or build cross-bracing beams and remove the rummble between the openings.
FYI Infrared lasers LIDAR is helpful here because of its excellent smoke-haze penetration and higher detail. Microwave side-looking radar might work but I think that the dust would either block or distorte the data. The sonar is probably used to probe the columns in near by buildings for hidden internal damage

Re:maybe offtopic

[Technician]

Due to the dual hazard of water at lower levels and no oxygen,leaves the safest way in is from the top. Material is removed layer by layer. Stories I have seen relating to both these problems have been covered in the media. Fires that flare up when a passage is opened indicates a smoldering oxygen starved fire. The subway tunnel under the trade center was sandbagged and pumping started indicates to me the lower portion of the basement is flooded up to or past the subway tunnels. See http://slashdot.org/article.pl?sid=01/09/23/172024 2&mode=thread for flooding info.

Terrible Sense of Levity

[brianvan]

I know Michael got reamed for this yesterday, but this once again is a story that uses an inappropriate introduction... with words like "nifty" and "(pun intended)" to refer to something regarding this tragedy...

I mean, I'm not one to be oversensitive, but come on people... I think that you disrespect the dead and the affected when you use cavalier words while referring to this situation. I only live 5 miles from Ground Zero and I saw the towers collapse with my own eyes. This makes me no more or less affected than any other American (save for those who lost a loved one in the disaster), but for a story poster to consistently make the same error in judgement like this obviously shows something about his regard for human life, for American pride, and for the people around him that are deeply affected by this terrible situation.

I ask not that we refrain from bringing it up, as I'm very proud of Slashdot in general for its coverage of this situation. But, to repeat the point from yesterday, there is nothing "nifty" about 6,700 innocent Americans dying in the most horrible way possible at the hands of a few highly irrational people... people whose peers live among us today waiting to give us our next big tragedy, our next week of continuous news coverage, our next spilling of innocent blood.

I mean, I don't want to be too dramatic, but our American flags don't just cheer us up and bring us together... they remind us of our freedom and the horrible things that happened because we insisted on having it. It may be 13 days later, but it's still a horrible thing. Please treat it accordingly.

Re:Terrible Sense of Levity

[Diabolical]

Please.... it were not 6.700 Americans but 6.700 Americans AND other nationalities (there were several hundreds of people working in the WTC that were NOT american)

It was not Michael that used these words. It was the person submitting the story. The word "nifty" i did not see...

Should /. withhold a story because someone is using a sense of levity in his introduction even if the story in itself is worthwhile?

Re:Terrible Sense of Levity

[gazbo]

Disgusting. I have written a more appropriate version:

Woeful and terrible how the WTC disaster has shone a light on technology (I flagellate myself at the mere hint of puns). LIDAR (Light Detecting and Ranging) is the optical equivalent of RADAR. It's being used to create hyper-detailed - yet morbidly terrible - maps of the WTC disaster site from an altitude of 5000 feet to detect shifts in the rubble as well as areas in danger of collapse."

In other words, shut up.

Re:Terrible Sense of Levity

[ergo98]

Yeah you ARE being oversensitive. The maps on CNN are nifty. It is amazing that technology moves forward by an event so tragic (in fact it's amazing that most of the technological advances tend to come in periods of war when we're really motivated to find ways to kill people). It if fascinating that a terrorist group used the latent energy in the WTC, coupled with jumbo jets, to achieve their deadly goal. It is amazing how the buildings held up for about an hour after being hit, until finally collapsing because of heat. It is very sad that 6000+ people died (though 1000+ were of other nationalities actually. It would probably seem more reasonable if you cut out the "6,700 innocent Americans" and left it as human beings), but it doesn't diminish from the amazing/neat/fascinating/stunning/awesome factors of the technologies or breakthroughs determined. Now if someone said it was "neat" that people were dismembered or something then you and your croonies would have a case to run to Slashdot shedding your crocodile tears and slowly waving your flag while singing Amazing Grace or something, but otherwise just save it: The overwhelming number of Slashdotters are just thinking "Aw STFU".

Re:Terrible Sense of Levity

[mosch]

There's nothing wrong with the description of the article here, and as far as "nifty" goes, you're offtopic here. That was in a thread posted by a different person in a different story on a different day.

Besides, one of the few things we can do at this point is try to learn from what happened, and try to make the best of a horrible situation. I don't know if the use of LIDAR to monitor the stability of rescue sites is new or not, but for the layperson such as myself it's a fascinating application of technology being used to help keep the rescue workers safe.

One thing you're going to have to realize is that there are going to be a ton of new technical information that will come from this. There will be studies on ways to prevent fuel from going everywhere (store it in ultra-strong bladder bags?) to building design to failure analysis to security analysis etc...

Science will do everything it can do to use this tragedy as a way to move forward and make life better and safer for all those of us who survived. At some point you'll have to accept that sometimes good things are the result of evil.

Re:Terrible Sense of Levity

[mosch]

The fuel additive is a bunch of hooey. Show me a fuel additive that would prevent the fire and explosion, but will still fire in an engine, and not a pop sci article, something from an engineering journal.

Re:Terrible Sense of Levity

[PD]

You know, normally I'd disagree with you. When the shuttle blew up I was getting a real kick out of all of the jokes that were circulating almost immediately. (What color were Crista McAuliffe's eyes? Blue. One blew this way, and one blew that way.)

But this one is different. I haven't heard a *single* joke about this one. I don't believe in respect for the dead. They are dead, so what do they care about jokes? Respect is for the living. 7 people and their families were affected by the space shuttle accident, a relatively small thing. In this case, our whole nation is depressed about it. Somehow I sort of doubt that we're going to see many jokes once that depression lifts. It really is just too awful to joke about.

Re:Terrible Sense of Levity

[brianvan]

Yea... I think that kinda sums up how I feel about it. I mean, don't get me wrong, if someone comes up with a really VILE dirty joke about it, I'm going to have to laugh in a way. But for the most part, this is not a light matter for anyone. I mean, even The Onion took a week off just because they felt their irony was inappropriate at a time like this. I would have normally disagreed with such a move, except this time we're dealing with something more severe than any of us have ever seen or read about.

I ain't gonna bitch out anyone who makes a post on here to a story with a dirty joke about it, because some people have a sick sense of humor and if you disagree about it, well then all that happens is that you disagree... I'm not going to the FCC or the FBI about it. But when the editor of the site lets a couple of "Wow, look at these nifty maps of the WTC site" go, I just felt I had to say, you know, that's not appropriate. I felt things were going to continue in that direction and I didn't want to see that happen. Furthermore, judging from some of the responses to my post, and from the moderation done to it, I'd have to say that not only was my concern valid, but that people here can be very disappointing beyond their OS zealotry and bitterness toward the world. Sad indeed.

(Not to knock the couple of people that posted something with a little bit of thought and class)

Re:Terrible Sense of Levity

[Chanc_Gorkon]

Sigh. The terrorists have won people. Now, I don't get me wrong, I am not disrespecting the dead here, but man we need to get over this. This LIDAR stuff IS cool. It's terrible we have to use something such as this on a disaster, but technology is what helps us learn things to either help prevent such disasters, or make the damage suffered in such events not as catastrophic. Now if you are directly affected, I understand if you are still mourning, but the general american should be over this by now....no, you shouldn't forget, but we need to get back to business.

It would not surprise people that technology is used after every disaster. Technology is what helped analyze damage created by a hurricane and help prevent the new stuff from being blown away as easily. There was a hurricane in 1900 that killed almost as many people as the WTC tragedy. It wasnt even as powerful as Andrew was, yet more people died in 1900 then in 1992 when Andrew hit. Yes there was still MAJOR damage and some loss of life, but the amount of deaths was minimized thanks to weather satellites and NEXRAD radar. Would it not be irresponsible for us to NOT use technology to try to prevent the catastrophic bulding collapses from happening when the next crazy terrorist get's pissed at us and decideds to use another plane as a missile? Yes, existing buildings would still be at risk and noone can ever plan far enough in the future to stop something like this happening (sure, planes like the planes used at the WTC are our biggest now, but whose to say that even bigger planes or heck spaceplanes with more volitile fuels would not be in common use 30 years down the road), but for a period of time, safety may be increased.

Technology is cool to us geeks because we realize it's a TOOL that can be used for non-life saving things or non human advancing things, and for things that make us better. This LIDAR stuff is nifty, cool, dope or whatever levity thing you want to put in here because it provides a in depth analysis of the building's destruction so we can prevent such catastrophic damage and loss of life from happening again if a plane were to hit another building on purpose or accidental.

Re:how is this done?

[mpe]

How do they monitor the site constatly from 5000 feet? is there a plane constantly circling around the site or is it done by a sort of balloon? can't this monitoring be achieved by satellites?

A satellite can't monitor such an area constantly, since Manhatten isn't on the equator.
The easiest way would be a teathered balloon.

Typical Computer Geek

[wiredog]

Probably get modded to minus infinity for this, but here goes.

He's a typical geek. In terms of personality we often are mildly sociopathic. We often don't connect with other people at all. And, unless we have been directly effected by an event, we are detached from it. We often live in our own little worlds, revolving around the latest cool tech. What we see is the coolness, the niftyness. We don't really see the people.

Re:Typical Computer Geek

[brianvan]

I can understand that perhaps you're an intellectual, and maybe not in touch with the general populace... but to be unapologetically antisocial... well, I'm sorry, but I find that saddening.

Re:Typical Computer Geek

[rark]

by definition antisocial people are unapologetically antisocial (in the more classic definition)

And the fact that nifty technology is used to clean up after a tragedy does not make it non-nifty. I'm sorry you can't separate the two ideas.

A mile long tether?

[BillyGoatThree]

"A satellite can't monitor such an area constantly, since Manhatten isn't on the equator."

And goodness knows we've only got one.

Satellite imaging is really the only way to get constant monitoring over an urban area. A mile long tether is inviting disaster (what's to keep planes from flying into it?)

Re:A mile long tether?

[FreeUser]

A NOTAM advisory maybe?

Not to mention positive ATC control, which is what all of the "enhanced bravo" airspaces around our major cities have become now that VFR traffic is forbidden beneath, or above, the old class-b shelf. Barring a major faux pas by ATC (or severe pilot error that would probably result in the scrambling of a couple of F-16s anyway) no plane is going to come anywhere close to a balloon tether.

Re:A new danger offtopic

[onepoint]

The bit of humor he gave was enough to make me smile. and that in it self, will give me a nicer day .

and yes, I live close enough to the WTC, saw it from my home also. Humor might be the best cure for what ill's me.

onepoint

LIDAR use before (VFX)

[malducin]

LIDAR technology is not soemthing new out of the blue. It has ben used quite a bit before. I saw it once at SIGGRAPH 99 (2 years ago). It's very useful for creating detailed 3D models. Kind of like a range finder, but it sweeps an area to get 3D range data out of it. It has even been used in films like in End of Days and What Dreams May Come. Here are a couple of articles from VFXPro.com

Panavision: Cinema in a New Light
Panavision's Panascan LIDAR System Integrates Cinematography

Interesting to see how this technology can be applied for a critical job. Especially when they start diging deeper below the level of the Hudson to detect any shifts.

Has been on CNN for a few days, check these

[ackthpt]

At the end of this bit of lame-filter-busting-fluff is a link to another representation on CNN, this has 3 views.

CNN Map

[Alien54]

While not as neat or as detailed; this CNN map is interesting as an overview of the site.

http://www.cnn.com/SPECIALS/2001/trade.center/dama ge.map.html

Note that a High speed line would nice to have when viewing this

Google Search Stats for 9/11

[msheppard]

Zeitgeist type stuff for the 11th.

My bad - 3 Lidar images mirrored from Newsday.Com

[ackthpt]

I saw the Lidar images on Newsday.com last week.

Mirrored here, here and here.

Time to eat some coffee...

Hyper-sensitivity does nobody any good

[securitas]

I understand that you are somewhat sensitive right now as many of us are. However if you read carefully, as others have pointed out, I in no way make light of the disaster. I refuse to be morose and publically flagellate myself because someone may misinterpret what I said, even though I said it very clearly.

Regarding wiredog's comments about being a typical sociopathic geek ... speak for yourself. Don't generalize your social limitations to the rest of the world. You may not think of people when you are wrapped up in the technology but others do. Why do you think I submitted the story? Technology exists to serve people, not the other way around.

FYI to both of you: I know many people who worked in the WTC and the surrounding areas. I still have not heard from some of them. Until I do, I still have to live my life as do many others. Allowing myself to be consumed by fear, loathing and grief is a disservice to the memory of all who perished.

Be careful who you judge, especially without knowing the whole story.

Re:Hyper-sensitivity does nobody any good

[brianvan]

I'm quite glad that you read this and took the time out to respond.

I'm do agree with you; this is not the time to be over-sensitive. And you did not make light of the disaster; to some extent, I think that the "pun intended" part was somewhat distasteful but only in the sense of juxtaposition of serious matters and a cheeky phrase like that. I guess it's a bit hypocritical, cause I thought it was funny when I heard that Howard Stern said that all the hookers in NYC should go downtown and give the rescue workers free blowjobs. I suppose that I wouldn't have made that wording choice after any length of time after the disaster. But it's not like a grudge thing or something like that - it's just your writing style. I guess it's all in the eye of the beholder.

As for michael... well, on a different level, he's supposed to "catch" things like that. As an editor with no bias to writing style, he definitely should have removed that "nifty" from yesterday's story, at least. For him to post two stories in a 24 hour period with a questionable juxtaposition of references to light words and a serious disaster... well, to some extent he's not doing his job. The stories were at least good. But he can edit the descriptions a little bit to keep things in a somber mood for the general populace. It's a tough job sometimes, but in my mind this would have been obvious: Just get rid of those words, they don't contribute to the "story" and they clash with the somber mood of the event itself.

All that stuff about patriotism... well, I'd be saying the same thing if it were an earthquake that killed 6,000 people.

Finally, that guy who said "Well, we're nerds, we're antisocial, we don't have to mourn"... well I told him, and I'll say it again: that's really sad. And that does not speak for all of us. I think it's terrible if you're a human being, you hear of something like this, and it doesn't make you upset. Yea, we can't cry about it forever, but I think it affects many of us deeply. I mean, it's just sad to think that on some level, we have NO support from these BOFH's that sit in their Fortresses of Solititude and only care about their IRC channels. They don't care about society, they don't care about freedom, and they don't care about America. To that extent, they're not Americans, even at this time when most people in the world agree, for right now, "We are all Americans".

With things like this, I wonder less why I hated some of the people in my (CIS) major in college... not all of them, just the people like this who are selfish and rude, unapologetically so. (You're not, though. Thanks for the response)

Re:And so the terrorists have won?

[brianvan]

This isn't a statement about life in general. I just think that the WTC tragedy will always be a somber event in history, just like Pearl Harbor or the sinking of the Titanic, etc. etc. Yea, we go on with life, and we're not upset about such things day-to-day, but I just think it's being under-sensitive to be using words like "nifty" in a story ABOUT the WTC disaster. Hey, I still think Lego blocks are nifty, and I have no problem with anyone calling them that... even the day of the disaster...

I'm sure the Irish don't refer to anything as nifty while mentioning Bloody Sunday in the same breath...

Lidar for navigation

[mattr]

There is more info about lidar here. Also, the everpresent nanites that act as airborne border patrols in Neal Stephenson's Diamond Age are supposed to use lidar for navigation. Interesting to note that in his book, those flying bots which need to communicate by radio have to trail whip antenna long enough to carry the appropriate wavelength.

It is already being used in autonomous robots for its superiority over sonar at Helpmate with funding from NIST, for use in hospital robots.