Tag: topographic map

Desktop Project Part 6: Psychedelic topographic Moon

By Phil Plait | March 31, 2012 7:00 am

[Over the past few weeks, I’ve collected a metric ton of cool pictures to post, but somehow have never gotten around to actually posting them. Sometimes I was too busy, sometimes too lazy, sometimes they just fell by the wayside… but I decided my computer’s desktop was getting cluttered, and I’ll never clean it up without some sort of incentive. I’ve therefore made a pact with myself to post one of the pictures with an abbreviated description every day until they’re gone, thus cleaning up my desktop, showing you neat and/or beautiful pictures, and making me feel better about my work habits. Enjoy.]

The Lunar Reconnaissance Orbiter, one of my favorite space probes ever, takes amazing high-res pictures of the lunar surface. But more than that, it can map the elevations of lunar features using shadows as a guide. Knowing the angles of the Sun, the Moon, and its viewing position, it can accurately gauge the elevations of the Moon’s surface as it takes image after image, orbit after orbit.

The scientists on LRO used that information to put together a wild topographic map of the Moon’s far side:

In this map, red represents stuff higher up, blue lower down. The resolution is decent: 100 meters across the surface (NSEW) and 20 meters vertically. Not enough to keep you from stubbing your toe if you’re walking across Mare Orientale, but enough to get pretty good info on the geological history of our nearby cosmic neighbor.

Of course, the picture I’ve displayed here — and even the embiggened version if you click it — doesn’t really convey the scale of this map. For that, you really need to check out the pan-and-zoom version. That lets you drill down into the data and see just how detailed this map really is.

And stay tuned. In a few months the LRO team will release a new version of this map; the spacecraft is still plugging away over the Moon, and there’s more way cool stuff yet to come.

Image credit: NASA/GSFC/DLR/Arizona State University


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CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures

The topographic Earth

By Phil Plait | October 18, 2011 1:30 pm

This is pretty nifty: a new elevation map of the Earth has just been released by NASA and Japan. It’s a "significantly improved" version of one that came out in 2009.

It uses Japan’s ASTER, the Advanced Spaceborne Thermal Emission and Reflection Radiometer, an instrument on board NASA’s Terra satellite. Terra is an Earth-observer, with detectors on board used to study various properties of our planet. ASTER looks both straight down and slightly behind the satellite’s track on the Earth is it passes. Over time stereo image pairs are created, and these can be used to create very high-resolution elevation maps (called topographic maps) of the surface of the Earth.

The new images are higher-res than before, and cover the Earth better to the tune of 260,000 more images. As an example of what can be done, they used it to make this map of the Grand Canyon:

[Click to enmesanate.]

One thing that struck me as funny when I read it: the coverage of ASTER’s observations goes from the Equator to as far north and south as 83° latitude… and they say that this is 99% of the Earth! That sounds odd, doesn’t it? You’d think the north and south poles of the Earth from 90° to 83° would be more than that, but in fact it’s true.

The portion of a sphere above a certain latitude line is called a cap, and the area of that cap depends on the latitude in question, and the radius of the sphere. I drew myself a diagram, fiddled with the numbers a bit, and found that the area of the Earth north of 83° compared to the surface area of the northern hemisphere is about 0.75%! So in fact, ASTER covered a bit more than 99% of the Earth’s surface, even if it never got past that 83°latitude.

Math! Surprising people since the time of Pythagoras.

Anyway, if you want to download the ASTER data yourself, you can: it’s public. Japan has a copy, and so does the USGS. I imagine it won’t be long before it’s integrated into Google Earth and all that too. Living in the future is pretty cool.

Image credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team


Related posts:

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CATEGORIZED UNDER: Cool stuff, NASA, Pretty pictures
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