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ESA's GOCE Satellite Provides Gravity Map of Earth

Soulskill posted more than 4 years ago | from the time-to-outsource-your-weight-lifting-to-india dept.

Space 119

kaulike writes "The European Space Agency's GOCE satellite, launched in March 2009, has provided a spectacular, highly detailed map of our favorite gravity well. This map shows the normalized surface of the earth as defined by gravity, showing the relative altitude differences from the average for each surveyed point. The article provides the helpful metaphor that a ball resting on this surface would not roll anywhere, even though there would be visual slopes, as gravity is equalized across the globe. There is a fascinating deep area in the Indian ocean (-100M) and a high area near Iceland (+80M), proving conclusively that our world is not homogeneous in terms of density (or practically any other measure). Does anyone know whether these anomalies correspond to known geographic phenomena? Deposits of heavy metals perhaps, or hotspots where the mantle is thinner? I know little about geodetic stuff, but I'm curious about the reasons for wrinkles in the data set."

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First? (5, Funny)

frank_adrian314159 (469671) | more than 4 years ago | (#32723810)

Gravity map? Heavy, man!

Re:First? (1, Funny)

Anonymous Coward | more than 4 years ago | (#32724238)

There's that word again; "heavy". Why are things so heavy in the future? Is there a problem with the earth's gravitational pull?

Re:First? (1)

jlar (584848) | more than 4 years ago | (#32727264)

I was just wondering whether athletes take gravity into account when trying to break World records. The best place to do athletics would then be near the Equator since the gravity is lower there by 0.5% compared with the poles. And that might give a centimeter or so in high jump and more in pole vault or long jump compared with mid-latitudes (potential energy and thus achieved height is a linear function of gravity near the Earth surface, meaning that a 0.5% drop in gravity means a 0.5% increase in height). The height above sea level is not really significant in this regard (but is probably due to other factors, mainly air density and temperature). So maybe Columbia would be a good place to break World records?

Assuming World records must be accomplished at the surface of the Earth.

known geographic phenomena (5, Funny)

nurb432 (527695) | more than 4 years ago | (#32723826)

No, but they do correspond to the location of the stargates.

Re:known geographic phenomena (1)

TooMuchToDo (882796) | more than 4 years ago | (#32724458)

SHHHHHHH! You're not supposed to tell them yet!

Re:known geographic phenomena (0, Troll)

forkazoo (138186) | more than 4 years ago | (#32727400)

No, but they do correspond to the location of the stargates.

Is "Stargates" a codename for yo momma's orifices? I only ask because, I'm certain she has sufficient mass to distort a gravity map. I feel quite ribald for saying this.

Actually, you can use it to find Monoliths (1)

wisebabo (638845) | more than 4 years ago | (#32728006)

In 2001 (the book) the Monolith was found at the center of a MASCON (mass concentration). I believe the Apollo space program needed maps of the moon's geoid because the moon is "lumpier" and considering the much lower orbits the command/service modules were in (no atmosphere remember) would cause significant deviations in their trajectory.

Yes "lumpier" is an official scientific term.

Re:Actually, you can use it to find Monoliths (1)

TheRaven64 (641858) | more than 4 years ago | (#32728482)

Are you sure? I'm fairly sure that I recall the monolith on the moon being called TMA1, standing for Tycho Magnetic Anomaly - it was found as a magnetic anomaly, not as a mass anomaly.

Re:known geographic phenomena (0)

Anonymous Coward | more than 4 years ago | (#32728204)

I remember a while back reading that an Olypic Games was held in the Nordic states, and that all the World Records were descroyed. Some scientists looked into it, and concluded that the gravity around that location was a tiny, tiny bit lower than the earth average, which was all it took for some of the records.

Where's a 1920x1200pxl Image? (2, Interesting)

Doc Ruby (173196) | more than 4 years ago | (#32723832)

That's a really nice image. Where can I find a 1920x1200 pixel image file of it to use as desktop wallpaper?

Re:Where's a 1920x1200pxl Image? (0, Insightful)

Anonymous Coward | more than 4 years ago | (#32723864)

Through the magic of clicking a few menu items in your favorite image editor.

Get off your lazy ass.

Re:Where's a 1920x1200pxl Image? (0, Informative)

Anonymous Coward | more than 4 years ago | (#32723968)

some people have a taste for pixel accuracy

Re:Where's a 1920x1200pxl Image? (0)

Anonymous Coward | more than 4 years ago | (#32726152)

MMMMMMM..... Tasty Pixels......

Re:Where's a 1920x1200pxl Image? (1, Flamebait)

Doc Ruby (173196) | more than 4 years ago | (#32724052)

If there's already one done somewhere, why should I duplicate the effort rather than download it? You really don't understand the Internet, do you, Anonymous jerk Coward.

Re:Where's a 1920x1200pxl Image? (0)

Anonymous Coward | more than 4 years ago | (#32725736)

Original AC here... What would make you think that someone releasing a science article would pander their output to fit on your screen? It hasn't been done before, so pony up and do it yourself, then paste a link for others that care about such eye candy, you Doc jerk Ruby :P

About a third of my desktop images are images that I've cropped to fit properly, or to get rid of some text or what-have-you, it really is quite simple and takes all of a minute.

Re:Where's a 1920x1200pxl Image? (2)

EdIII (1114411) | more than 4 years ago | (#32726518)

Why is this modded insightful?

The original image is 786x427. If you expand that up to HD, or in this case 1920x1200 it would result in a very pix-elated image. It's not lazy to ask for a higher resolution image, and that part of the post is the difference between +flamebait, and +funny.

Re:Where's a 1920x1200pxl Image? (1)

oldspewey (1303305) | more than 4 years ago | (#32724438)

Not the same, but equally cool:

http://www.google.com/mars/

Re:Where's a 1920x1200pxl Image? (1)

t3h Odd one (1295721) | more than 4 years ago | (#32725148)

Where's the street view!? We've sent how many rovers there and they haven't even converted 1% of the images for Mars Street view!?

Map of our favorite gravity well (1)

QBasicer (781745) | more than 4 years ago | (#32723922)

And what well is that? Apparently I'm missing something, and I suspect others the same thing.

Re:Map of our favorite gravity well (1)

UnknownSoldier (67820) | more than 4 years ago | (#32723950)

YHBT.

The idiot AC doesn't understand upsampling an image (Gimp > Rescale) isn't the solution you are talking about, namely one of having a higher pixel density.

Re:Map of our favorite gravity well (0)

Anonymous Coward | more than 4 years ago | (#32724026)

The well of an Indertictor Class Imperial Medium Frigate [wikia.com] of course.

Re:Map of our favorite gravity well (2, Informative)

UnknownSoldier (67820) | more than 4 years ago | (#32724048)

Not quite full HD but still is a higher res: 1081 x 541
  http://www.usna.edu/Users/oceano/pguth/website/so432web/ww15mgh.jpg [usna.edu]

Re:Map of our favorite gravity well (1, Funny)

Anonymous Coward | more than 4 years ago | (#32726082)

Completely worthless map. The US is not in the center.

Re:Map of our favorite gravity well (0)

Anonymous Coward | more than 4 years ago | (#32728122)

Which surprised me, I would have expected all the obese people to contribute to a stronger gravitational pull

Re:Map of our favorite gravity well (0)

Anonymous Coward | more than 4 years ago | (#32724148)

Your favorite gravity well should be our planet, you know, Earth.

The thing you're missing would be a science education, and you can find one back in high school.

Re:Map of our favorite gravity well (1)

gmuslera (3436) | more than 4 years ago | (#32725018)

If i have one of this ones [xkcd.com] (yada yada oblig xkcd et al), i would pick the sun as favorite.

Re:Map of our favorite gravity well (1)

nacturation (646836) | more than 4 years ago | (#32726608)

And what well is that? Apparently I'm missing something, and I suspect others the same thing.

Well, given that I suspect the name of the satellite sounds suspiciously close to "goatse", I don't want an image of this gravity well they speak of.

cool (4, Interesting)

john_uy (187459) | more than 4 years ago | (#32723932)

this is quite a very informative article.

my question though from the image produced is that the metres/meters scale shows how "strong" or "weak" the gravity is from the normalized sphere? how is it in the unit of metres/meters? i would appreciate if someone could explain the map more detailed (i probably need another explanation from the article to understand it more.)

the goce satellite is cool. i mean i didn't realize that we have technology such as xenon ion thrusters. i thought they were limited to star trek. my ignorance. :((

thanks in advance. :)

Re:cool (4, Informative)

demonbug (309515) | more than 4 years ago | (#32724086)

The map is showing the deviation from an ideal spheroid that would result in the observed gravity variation. So, positive meters basically means that if the Earth were made of stuff of a uniform density, the surface of the earth would be this many meters above the ideal surface (gravity is weaker here than expected). Conversely, negative meters means gravity is stronger here than expected, and so correlates to a "low" (low elevation being closer to the center of mass of the earth, meaning stronger gravity).

The map is essentially showing what the surface of the earth would look like if all variation in gravity (what they observed) was due to variation in the shape of the earth, rather than density. At least, I think that is what they are showing - I don't think the article actually states if this is raw data or if it has been processed (to apply a free-air correction, for example, which would remove variability due to the actual variations in elevation of the earth's surface).

Make sense? It isn't as complicated as my half-assed explanation might make it seem (well, it is complicated, but the concept is simple).

Re:cool (1)

UnknownSoldier (67820) | more than 4 years ago | (#32724136)

Re:cool (2, Informative)

maeka (518272) | more than 4 years ago | (#32724324)

No, because that image shows one how height above the ellipsoid (not spheroid as someone said above) model of the earth (as used in GPS / etc.) minus the geoid model deviation (what these satellites are, in effect, measuring) equals your orthometric height (what most people call "elevation").

I don't believe this helps the GP's query, because it doesn't explain what the geoid model is.

What most people never think about is that old-school surveying (with a conventional level) always, even before we understood that the earth's gravity varied, compensated for the variation. A surveyor's level, be it an old one where the circular plate is made level with a spirit bubble or a newer one where the recticle floats and self-compensates, is always looking perpendicular to the line between it and the center of gravity. Everyone always assumed, back in the day, that this really meant the center of the Earth, but the positive side effect is that elevation measurements "carried" with a surveyor's level were always compensating for these differences in gravitational potential.

So much so, that all the major geoid models used to this day are heavily based upon high-precision GPS observations (of height above the ellipsoid) on benchmarks possessing elevations leveled in.

Re:cool (1)

john_uy (187459) | more than 4 years ago | (#32724174)

thanks. got it. :)

Re:cool (-1, Flamebait)

Anonymous Coward | more than 4 years ago | (#32724356)

Why do you read some random dude's mumblings instead of the article? Just because his post is more recent than anything else online doesn't make it better. The Earth's deviation from the ideal spheroid is many kilometers, not the 100m of the map, so he doesn't know shit.

Re:cool (0)

Anonymous Coward | more than 4 years ago | (#32724346)

I am not sure (I agree that the article was not too clear), but my interpretation of the article was slightly different, in that positive geoid height means stronger local gravity, and negative height means lower gravity.

I drew this conclusion from the following statements:
"It traces gravity of equal 'potential' "
and
"The geoid is of paramount interest to oceanographers because it is the shape the world's seas would adopt if there were no tides, no winds and no currents."

My explanation was that the regions of higher gravity resulted in a positive geoid height because you would have to move further away from the centre of the Earth to experience the "standard" gravitational acceleration of 9.8m/s^2. As for the water shape, well it seemed to make sense to me -- water being mostly incompressible as it is -- that you would have a larger buildup of water around the regions of high gravity (and hence a positive height), and troughs in the overall water table at the regions of lowest gravity since the water would be pulled away from there to the higher gravity areas.

Re:cool (0)

Anonymous Coward | more than 4 years ago | (#32724544)

The map is showing the deviation from an ideal spheroid that would result in the observed gravity variation.

No it isn't. Think of a contour on a regular map. A contour is a line connecting points of equal height. The data from the satellite was made into a single 3D "contour" connecting points of equal gravitational acceleration. The colour map in the article shows the difference in height between the actual gravitational "contour" and the ellipsoid ideal gravitational "contour" that you would get if the earth was homogenous. (The ideal contour is an ellipsoid because of the bulge at the equator.)

Re:cool (1)

tyldis (712367) | more than 4 years ago | (#32726980)

TFA reports the data has been collected over two months which should give several repeated measurements over the same area and thus compensate for most variable things.
That noted, the project has been receiving science data from the gradiometer (known as the EGG) for about a year now with inly minor interruptions.

The GOCE is a spectacular satellite, as it's low 250km orbit means it actually suffers from drag. Hence the Xenon Ion Thruster which keeps it from falling down. Normally a satellite does not have to worry about aerodynamics, but GOCE even has wings to keep it stable.

high points are high gravity. (Re:cool) (2, Informative)

darkonc (47285) | more than 4 years ago | (#32728092)

uhm, no. the geoid is at negative height where the gravity is WEAKER. The geoid consists of a surface where a ball would never roll because the gravity differential would counteract the slope (or vice-versa)...

Think of it another way... The observed 'center' of gravity is always perpendicular to the slope of the geoid.

Thus consider a piece of slope tilted like a forward slash ( / ) The gravity would have to be stronger on the right hand side to hold the ball flat against the slope... Thus the gravity is stronger on the 'high' side, and weaker on the 'low' side.

Isn't that backward? (1)

cnaumann (466328) | more than 4 years ago | (#32728730)

If an area has to be higher than the idealized surface to be 'level' (to keep a ball from rolling) won't that be an area that has stronger local gravity?

Interesting... the Indian ocean is nearly 100 meters too shallow.

Re:cool (0)

Anonymous Coward | more than 4 years ago | (#32728886)

the surface of the earth would be this many meters above the ideal surface (gravity is weaker here than expected). Conversely, negative meters means gravity is stronger here than expected, and so correlates to a "low" (low elevation being closer to the center of mass of the earth, meaning stronger gravity)

That was also my original intuition. Unfortunately, most explanations do not make it explicitly clear (including the article and Wikipedia), but a higher geoid means stronger gravity and a lower geoid means weaker gravity.

http://geophysics.ou.edu/solid_earth/notes/geoid/earths_geoid.htm/ [ou.edu]

Re:cool (1)

phantomfive (622387) | more than 4 years ago | (#32724104)

my question though from the image produced is that the metres/meters scale shows how "strong" or "weak" the gravity is from the normalized sphere?

That is my understanding, based on the explanation and informative diagram at the bottom of the article. :)

Re:cool (1)

JesseMcDonald (536341) | more than 4 years ago | (#32724158)

I'm no expert, but it looks like they calculated an isosurface (a surface where every point has the same perpendicular gravitational pull) and colored their map based on the difference in height between this isosurface and the surface of the normalized sphere. On a normalized sphere (e.g. at sea level) gravity would be stronger where the isosurface is higher and weaker where the isosurface is lower.

Re:cool (0)

Anonymous Coward | more than 4 years ago | (#32724168)

It's the surface of equal gravitational acceleration. If the Earth's mass was homogeneously distributed (eg a uniform solid), the equipotential surface would be a perfect spherical surface. Since the earth's mass is lumpy, you don't get a perfect sphere for the equipotential surface. GOCE has chosen to represent the situation by telling you how far above (or below) the "perfect sphere" you have to go in order to stay on the equipotent surface. It makes sense if you think about it. If have to go "below," that indicates that gravity is weaker ar that point. The reverse is true too.
   

Re:cool (0)

Anonymous Coward | more than 4 years ago | (#32724492)

Is everyone a moron today? (And not just you, most of the +modded comments get it equally wrong. I'm replying to you because nobody believes an AC contradicting a coherent-sounding (but wrong) numbered user.)

PROTIP: you get potential of a conservative field by integrating it -- this means that isosurfaces of the field itself ("the surface of equal gravitational acceleration") and isosurfaces of the potential ("the equipotential surface") are not in general the same.

According to tfs, it's an equipotential, BTW.

Re:cool (0)

Anonymous Coward | more than 4 years ago | (#32724212)

Holy fucking cow, can you not read TFS?!

Picture a point mass (say, the mass of the Earth), and the field it generates.

Now imagine an Earth-sized sphere centered on the same point. See how every point on the surface has the same potential?

OK, now if we're not moving too fast... Replace the point mass with the Earth; now the field is "lumpy", right?

The equipotential surface is correspondingly perturbed in space (you know, physical space; 3 axes, units of length all 'round?). Now what the fuck do you propose the dimension of a geometric perturbation in physical space should be if not length?

Re:cool (0)

Anonymous Coward | more than 4 years ago | (#32724972)

The problem is one of near common sense. The scale doesn't seem to 'add up'. Is it really the case that the largest difference in gravitational pull spans a measely 200meters?

Atlantis (0)

Anonymous Coward | more than 4 years ago | (#32723974)

That's Atlantis down there, south, southwest from Iceland. Sunk into the ocean by a sudden change of Earth's gravity well.

Interesting Pattern Near the Ring of Fire (5, Interesting)

BJ_Covert_Action (1499847) | more than 4 years ago | (#32724012)

If you look at the map, a lot of the high-gravity areas tend to appear near highly volcanic areas like the ring of fire (and, as the reader pointed out, Iceland). I wonder if this has something to do with more magma being closer to the surface in those areas...or something similar?

Re:Interesting Pattern Near the Ring of Fire (1)

ALeavitt (636946) | more than 4 years ago | (#32724050)

Perhaps it is due to the effect of having two tectonic plates in close proximity to each other. For instance, in the immediate vicinity of a subduction zone the satellite would essentially see two stacked tectonic plates, which could account for the differences in observed density.
Anybody with more than a freshman-level understanding of geology want to correct me?

Re:Interesting Pattern Near the Ring of Fire (1)

AlXtreme (223728) | more than 4 years ago | (#32727650)

Except that the two plates from which Iceland has formed (American and Eurasian?) are moving away from each other instead of moving together and one overlapping the other. Besides, if this were the case the "density" would be greatest or weakest along all fault lines, which isn't the case.

Re:Interesting Pattern Near the Ring of Fire (4, Funny)

BJ_Covert_Action (1499847) | more than 4 years ago | (#32724074)

Oh, I'd also like to point out, just for the sake of inflammatory goodness on the interwebs, that America is entirely green and homogenous, thus scientifically proving that we are the best at gravity as well as everything else. Also, we officially qualify as normal and neutral so take that all you backwards-ass, long-haired, rock-and-roll loving, high/low gravity hippy nutjobs on the rest of the continents! Give me back my 9.806 m/s^2 .... I mean...32.174 ft/sec^2....aww hell, I made it back to my OP.

Re:Interesting Pattern Near the Ring of Fire (0)

Anonymous Coward | more than 4 years ago | (#32724172)

Well I was hopping it explained why Americans are fatter than the rest of the world but by this we should be getting more of a natural gravity work out than all of Europe at least.
Go figure.

Re:Interesting Pattern Near the Ring of Fire (2, Funny)

Arthur Grumbine (1086397) | more than 4 years ago | (#32724454)

Well I was hopping it explained why Americans are fatter than the rest of the world...

I fail to see how your hopping would explain anything besides minute fluctuations in the gravity between your feet and the ground, and your predilection towards hats with ear flaps.

Re:Interesting Pattern Near the Ring of Fire (1)

jlar (584848) | more than 4 years ago | (#32728686)

"I'd also like to point out, just for the sake of inflammatory goodness on the interwebs, that America is entirely green and homogenous, thus scientifically proving that we are the best at gravity as well as everything else."

Please take a look at central Africa and tell me again that green and homogenous is a sign that you are best at gravity as well as everything else;-)

Re:Interesting Pattern Near the Ring of Fire (1)

demonbug (309515) | more than 4 years ago | (#32724160)

Heat. Hot rock is less dense than (similar) cold rock, so if you have a lot of hot rock near the surface you are going to have a gravity low (which appears as a "high" elevation on this map). In theory, anyway. I would have expected a much stronger signal all along the MORs; this doesn't appear to be the case.

Obviously there are many other factors too, but that can explain a tendency towards higher elevations (weaker gravity) in volcanic regions.

Re:Interesting Pattern Near the Ring of Fire (1)

phantomfive (622387) | more than 4 years ago | (#32724266)

I wondered that too, but if you look at a volcano map [si.edu] , it doesn't seem to correspond very well with high volcanic areas. Compare the areas in Africa and Central America that still have active volcanoes, even though they are not high gravity. The map doesn't correspond at all to plate tectonics, as far as I can tell from my limited understanding.

It DOES however seem to correspond fairly well with this map of the earth's deformation [wikipedia.org] . Places on the earth that have a surface distance farther from the middle of the earth also have stronger gravitational pull. Makes sense to me.

Re:Interesting Pattern Near the Ring of Fire (1)

BJ_Covert_Action (1499847) | more than 4 years ago | (#32724350)

Wow, yeah, it does correspond to the deformation map really well...good catch. Thanks.

Re:Interesting Pattern Near the Ring of Fire (3, Insightful)

treeves (963993) | more than 4 years ago | (#32724914)

it corresponds really well because it is exactly an image of the same thing, just an earlier, less accurate version.

Re:Interesting Pattern Near the Ring of Fire (2, Interesting)

CaroKann (795685) | more than 4 years ago | (#32724636)

It looks like there could also be a relation to continental movements in some areas. The cooler colored areas appear to be trailing behind fast moving continental plates, almost like a backwash. Look at the southern tip of India, which is quickly moving north into Asia. There is a cool area to the south of the California plate, which is moving north. There is another cool area off the east coast of North America and to the east of the Caribbean.

Re:Interesting Pattern Near the Ring of Fire (0)

Anonymous Coward | more than 4 years ago | (#32729140)

Short answer: yes.

These long-wavelength (1000s of km) variations in the geoid are thought to be due mainly to differences in the density of rocks in the mantle, which is in turn thought to be controlled to a large degree by subtle variations in temperature. Magma in volcano-related quantities isn't so much an influence at this scale, because the fraction of melt within the mantle is usually extraordinarily small (it's probably a percent or lower by volume in most cases). The mantle is red-hot and deformable, but not primarily liquid. Even so, the geoid anomaly near Iceland isn't a coincidence. The volcanism there probably relates to what's going on underneath and that to the geoid expression. Anyway, these sorts of variations in mantle properties (temperature, density, melt concentration) can be observed indirectly via techniques such as seismic tomography (which uses sound from earthquakes in the Earth somewhat like a medical CAT scan), and they correspond reasonably well with the geoid. A large part of what is seen in the geoid at this broad scale is probably related to the convection system within the mantle.

Other effects are seen at a smaller scale from such features as oceanic trenches, ocean ridges, the edges of the continents, mountain ranges, etc.

Got KML? (4, Interesting)

BigDXLT (1218924) | more than 4 years ago | (#32724020)

I'd love to zoom around in google earth to look at this.

Christiano Ronaldo (1)

sir_eccles (1235902) | more than 4 years ago | (#32724070)

Other anomalies include several mobile high gravity areas that seem to track Christiano Ronaldo and several other soccer players.

Re:Christiano Ronaldo (1)

L4t3r4lu5 (1216702) | more than 4 years ago | (#32728992)

So, the greatest danger to mankind isn't the LHC creating a black hole, it's the Arsenal changing rooms... For the same reason?

I would never have expected that. (Spanish Inquisition jokes on a postcard, please!)

The U.S. military already has one of these (3, Informative)

tlambert (566799) | more than 4 years ago | (#32724076)

The U.S. military already has one of these

It's used in inertial navigation for weapons systems. Interestingly, the inertial navigation software itself is available as source code for download, but the data of the map itself is classified to prevent its use by non-U.S. aggressors. Also, for what its worth, the military data resolution is far better than the 100km between data points, as it is with GOCE, but is the resolution falls off on non-projected weapons trajectory route splines.

See also the geoid from the earlier GRACE observations (animated spinning globe) which were 322km resolution, along with a more technical discussion of GOCE:

        http://www.scientificblogging.com/planetbye/grace_goce [scientificblogging.com]

-- Terry

Re:The U.S. military already has one of these (1)

TooMuchToDo (882796) | more than 4 years ago | (#32724480)

What satellite/aircraft did the US military use to obtain the data at a higher resolution?

Re:The U.S. military already has one of these (1)

John Hasler (414242) | more than 4 years ago | (#32724776)

They don't necessarily have higher resolution data everywhere.

Exactly (2, Informative)

tlambert (566799) | more than 4 years ago | (#32725704)

Exactly... "the resolution falls off on non-projected weapons trajectory route splines".

You get very good data for the areas in which you want to fly your birds, and lesser data for where you don't expect to do that. This is necessary to, for example, use inertial guidance rather than active TFR in a cruise missile and keep it below the enemy radar.

-- Terry

Re:The U.S. military already has one of these (0)

Anonymous Coward | more than 4 years ago | (#32725272)

but the data of the map itself is classified to prevent its use by non-U.S. aggressors

Nice Freudian slip there, mate

Re:The U.S. military already has one of these (1)

highways (1382025) | more than 4 years ago | (#32726912)

> Interestingly, the inertial navigation software itself is available as source code for download

[[Citation Needed]]

Re:The U.S. military already has one of these (0)

Anonymous Coward | more than 4 years ago | (#32727332)

Where is this inertial navigation system source?

Drill south of Sri Lanka (0, Offtopic)

marianomd (1518677) | more than 4 years ago | (#32724100)

There must be some big cave under there.

Re:Drill south of Sri Lanka (0)

Anonymous Coward | more than 4 years ago | (#32724248)

There must be some big cave under there.

Indeed. If you go, make sure to tell Cthulhu that we all said hi! :)

LOST (-1, Troll)

poly_pusher (1004145) | more than 4 years ago | (#32724120)

Finally! The Lost ending makes sense! Well... maybe not, but they could of scammed another few seasons had they heard about this earlier.

wonder why they duplciated US GRACE satellite? (1)

peter303 (12292) | more than 4 years ago | (#32724218)

ESA must be rolling in money to repeat US experiments. The US experiment repeats its experiment every few months. They detect the gravitation signatures due to mass change like melting/flowing glaciers.

Politics (1)

servognome (738846) | more than 4 years ago | (#32725302)

Science has become politicized; sure the US already did these experiments but it doesn't guarantee European scientists get timely access. Gathering your own information offers a competitive advantage, whether it's for the prestiege of discovery, industrial value, or the ability to interpret data first to further political goals

Re:wonder why they duplciated US GRACE satellite? (1)

atamido (1020905) | more than 4 years ago | (#32725918)

I believe this data is higher resolution than what was available to the public via the GRACE project. That said, the first thing I thought when I saw this was "why is this new?"

Re:wonder why they duplciated US GRACE satellite? (3, Interesting)

mbone (558574) | more than 4 years ago | (#32726056)

Grace and GOCE are completely different experiments, which measure different (but related) things about the Earth's gravity field. Grace tracks the motions of a pair of satellites, which GOCE uses pairs of accelerometers. Different data types, different measurement errors, different types of systematic errors. I think it is well worth running both experiments.

I hope we can get hand held models soon (0, Offtopic)

abbynormal brain (1637419) | more than 4 years ago | (#32724276)

I think there is a strong-to-weak shift under my computer desk at home that might explain why one of my balls hangs lower than the other and would like to verify this.

What is the data set showing me? (1)

Jason Pollock (45537) | more than 4 years ago | (#32724314)

Is it height over/under radar measurement?
Is it height over/under normalised ellipsoid (no terrain)?
If I see a red, does that mean that the satellite saw a stronger or weaker gravitational force at that location?

Re:What is the data set showing me? (0)

Anonymous Coward | more than 4 years ago | (#32725364)

It's the deviation of the geoid (look it up on Wikipidedia) from a best-fit ellipsoid.

Re:What is the data set showing me? (1)

mbone (558574) | more than 4 years ago | (#32726024)

The data is a model of what sea level would be, for a completely water covered Earth, assuming that the oceans had uniform density and no currents, minus the mean sea level. This sounds complicated, but it is pretty easy to calculate, assuming you have the gravity data.

Lovecraft was wrong. (1)

FiloEleven (602040) | more than 4 years ago | (#32724764)

Looks like R'lyeh lies beneath the Indian ocean...

Fish in the data? (0)

Anonymous Coward | more than 4 years ago | (#32724850)

Does anyone else see a yellow fish at the bottom of Africa (with an orange fin?) This has obviously been left by aliens...

Mining (0)

Anonymous Coward | more than 4 years ago | (#32725060)

It would be kind of neat to see the effects of mining heavy minerals in a given area. They are mined in one area and transported to another etc.

So I'd expect to see the pre-mining images showing normal to greater gravity and the after-mining images to show lower to normal(respectively) gravity.

Commercial uses (1)

or-switch (1118153) | more than 4 years ago | (#32725416)

I remember in college physics the prof talked about how oil companies use small deviations in gravity to help identify where large oil deposits might be. Oil is much less dense than rock, so maybe that large well in the Indian ocean is a huge oil deposit?

If so? Drill, Baby, Drill. (1)

/dev/trash (182850) | more than 4 years ago | (#32725528)

Looks like someone's going to be made a democracy here soon!

Re:If so? Drill, Baby, Drill. (0)

Anonymous Coward | more than 4 years ago | (#32725580)

Oh cool!

Is it the United States? They could use a democracy.

Re:If so? Drill, Baby, Drill. (1)

IflyRC (956454) | more than 4 years ago | (#32729538)

Surely you jest - I voted for Change.

Re:Commercial uses (1)

mbone (558574) | more than 4 years ago | (#32726070)

The easiest way to find oil in gravity maps from what I understand is to look for salt domes (big bubbles of salt), which are much less dense than the surrounding rock.

The big low in the Indian ocean is thought to be related to subduction and may even be a "wake" from the recent passage of the Indian subcontinent as the plate drifted North. I don't think it is a huge salt dome.

Your Mom? (0)

Anonymous Coward | more than 4 years ago | (#32725782)

"Does anyone know whether these anomalies correspond to known geographic phenomena? Deposits of heavy metals perhaps, or hotspots where the mantle is thinner? I know little about geodetic stuff, but I'm curious about the reasons for wrinkles in the data set."

Your Mom?

Interpreting gravity maps (1)

mbone (558574) | more than 4 years ago | (#32725942)

There is a fascinating deep area in the Indian ocean (-100M) and a high area near Iceland (+80M), proving conclusively that our world is not homogeneous in terms of density (or practically any other measure). Does anyone know whether these anomalies correspond to known geographic phenomena? Deposits of heavy metals perhaps, or hotspots where the mantle is thinner? I know little about geodetic stuff, but I'm curious about the reasons for wrinkles in the data set."

Something that is maybe not so clear from the discussion in TOA, this is an accelerometer mission, and thus reveals a high pass filtering (AKA high-harmonic geoid signatures) of the gravity field. I am not sure if the geoid map in the BBC article is entirely from GOCE data, or if it has other data filling in the low spatial frequencies - it looks pretty similar to older geoid maps [nga.mil] .

You might want to read this paper [esa.int] , which points out that

"The interpretation of GOCE geoid and gravity anomaly maps in terms of structure and dynamics of the Earth is
neither simple nor straightforward.
"

You can see things like typography, sea-mounts (modern gravity data is very good at detecting these), mountain ranges (these are like icebergs, made of lighter material with deep roots, and so are typically actually geoid lows), subduction zones, etc. Since what's going on may be determined by mass / density changes in the deep mantle, figuring out what the observed structures mean can be tough.

However, the scientific interest in these gravity data largely centers around changes in gravity, and many of these are more straightforward. Among the signatures of interest are ocean current changes (might change the dynamic sea level by 10 cm), ice formation and melting (for example, of the Greenland ice sheet), and the global water balance on land (if it rains, it changes the mass loading of the ground, and thus the geoid). Data such as these, and the data from GRACE, are becoming more and more important in the study of global geodynamics. The literally show what's happening on the ground, in basically real time.

Re:Interpreting gravity maps (0)

Anonymous Coward | more than 4 years ago | (#32727698)

You can see things like typography

That's some damn fine resolution!

Why don't Himalayas show up stronger? (1)

Thagg (9904) | more than 4 years ago | (#32726674)

GOCE shows slightly stronger gravity in the Himalayas area, but is only a few tens of meters different from the elliptical earth. The mountains are thousands of meters high over a very extended area. I would expect them to show up more strongly. Does this imply that the earth I'd proportionally less dense under those mountains?

Re:Why don't Himalayas show up stronger? (0)

Anonymous Coward | more than 4 years ago | (#32727206)

Yes. The continental crust of which the mountains are made is the least dense of all rock material. The mountains also have roots, extending about as far downwards to the mantle as the mountains are high.

Application: Mean Sea Level for your GPS Receiver (1)

highways (1382025) | more than 4 years ago | (#32726878)

The other application of the Geoid is that it is essentially the "Mean Sea Level" across the globe.

This is essential for you GPS Receiver - the height calculated by a GPS receiver is the height above a theoretical ellipsoid that has pretty much the same shape of the earth. However, the geoid is used to calculate the difference between this "Ellipsoidal Height" and the "height above sea level" that is reported by receivers - sometimes known as "undulation". Without it, Brisbane, Australia would report being about 40m above the water when out on the Bay in a boat.

GPS Receivers typically use a lookup table for it, but can be calculated from scratch using a geoid model such as EGM96 [wikipedia.org] using Spherical Harmonics [wikipedia.org] . Of course, there is an open source implementation of it in C [sourceforge.net] and MATLAB [sourceforge.net] .

Noticed the symmetry? (0)

Anonymous Coward | more than 4 years ago | (#32726886)

Mm..., if you look at the globe the deep area in the Indian Ocean is exactly across the globe
from the triangle of deeps in North America, and the high near Iceland is almost across the globe
from Ring of Fire, there is a clear symmetry, which is almost perfect if take into account
the high between Africa and Antarctica.

That explains it (1)

JavaBear (9872) | more than 4 years ago | (#32726922)

...Why my diets are failing at any rate :)

Re:That explains it (1)

L4t3r4lu5 (1216702) | more than 4 years ago | (#32729006)

Indeed! You're not gaining weight: Local gravity is just higher!

Some background: The Satellite Itself (5, Informative)

highways (1382025) | more than 4 years ago | (#32727134)

It's worth taking a read [bbc.co.uk] of the satellite itself. Apparently, the accelerometers themselves (3 pairs of them) are mounted to within one picometre (that is micro-micro-metre). Gravity measurements are to within 10^-13 G. All pushed ahead by a cool xenon ion engine :)

That's some serious engineering precision. A bit more than your average accelerometer [sparkfun.com] in your iPhone.

There's a bit more on how it works in this article [bbc.co.uk] .

Of course, the raw data looks a lots uglier [bbc.co.uk] than the beautiful image of the final result, but if the research is for climate change, then manipulating raw data is what they do best ;)

Re:Some background: The Satellite Itself (2, Interesting)

Zoxed (676559) | more than 4 years ago | (#32728494)

> That's some serious engineering precision.

If that is your cup of tea, then you will be interested in the in-development https://secure.wikimedia.org/wikipedia/en/wiki/Gaia_probe [wikimedia.org] : it will measure arcs of the order of the diameter of a hair from 1000 km away !!

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