I work somewhat in the field and one important reason that the SRTM dataset is 90 meters is that the data volume is lower. In fact the SRTM global mosaic at 90m is still about 120 gigabytes of data.

Its actually quite a bit of a problem that this new GDEM v2 is at 30m since that means that its size would be 9 times larger if it covered the same area but as you mention this dataset covers up to 83 latitude which in the WGS84 coordinate system means quite a bit more map space.

Additionally I have heard from other people who have read the validation report that the real resolution is quite a bit less than 30 meters and that the choice of 30m pixels is based on the ASTER sensor not on the meaningful resolution for the dataset.

All that said, that this dataset covers more than the widely used SRTM is important since the 60 latitude limitation on that excludes many northern areas of the world.

Also, Don, Mr. Phil likes to coin his own neologisms for ‘embiggenate’. So if you’re expanding an image that includes mesas, you are ‘enmesanating’ the image.

A possibly simpler way of saying it is that at the poles, the land:sea ratio is disproportionately high (at ~1:1) than the planet as a whole (~29:71).

Anyway, if you want to download the ASTER data yourself, you can: it’s public.

… but it’ll take you hours to figure out how, and you’ll have to create a bunch of thoroughly unnecessary accounts to do so.

I can’t for the life of me imagine why they’re making it this difficult. The Blue Marble images, by comparison, are easily accessible and directly downloadable over HTTP, FTP, and bittorrent.

There’s barely any land in the Arctic above 83ºN, but in the Antarctic below 83ºS it’s 100% land (with maybe the odd frozen lake below the ice cap). I’ll net those out and assume that half of the total area missed is land (i.e. 0.375% of the globe).

Hence the coverage figure needs to account for that missing chunk. A quick search reveals that land covers 29.22% of the globe, but ASTER has missed that 0.375% of the global land coverage at the poles, so by my rough calculation they’ve actually only covered 98.71% of the _landmass_, compared to 99.25% of the planet.

i.e. 100 * (29.22 – 0.375) / 29.22

Besides what Wikipedia says about John Wesley Powell being a U.S soldier, geologist, explorer of the American West, and director of the major scientific and cultural institutions including the first known passage through the grand canyon and serving as second director of the US Geological Survey (1881-1894) and being director of the Bureau of Ethnology at the Smithsonian Institution for a period of time I don’t know what type of man John Wesley Powell was but he’s recorded as saying the following regarding this puzzle piece within the Earth known as the Grand Canyon.

“The wonders of the Grand Canyon cannot be adequately represented in symbols of speech, nor by speech itself. The resources of the graphic art are taxed beyond their powers in attempting to portray its features. Language and illustration combined must fail.”

&

“You cannot see the Grand Canyon in one view, as if it were a changeless spectacle from which a curtain might be lifted, but to see it you have to toil from month to month through its labyrinths.”

John Wesley Powell 1834-1902

It is amazing to actually imagine how powerful an image like this could be to a man living at that time period. I wonder what John Wesley Powell would have thought about ASTAR

I mean I know google earth has been around for awhile. . . but really. Who cares.
The Earth Never Gets Too Old To See!

Math! Surprising people since the time of Pythagoras.

That made me smile. What a great phrase!

There must surely be infinite wonderful relationships throughout geometry and all of mathematics for that matter. But perhaps the sphere/ball(?) is capable of giving us the most . . . easily seeable (?) relationships of space to points to lines.

The equality of the ‘derivative of the area of circle’ and ‘the circumference of that circle’ is just one I learned and remember!

For me it is difficult to understand the concepts and the level of deduction which can be shown on paper of how and why measurements evolve with respect to other elements of equations but it is always a moment of awe when relationships are discovered.

sin 83˚ = 0.992546 from comment #1.

I don’t have my scientific calculator to check if his math is correct.

I know I know:
1. Argus is probably right and undoubtedly yields vastly superior mathematical skills
2. Don’t ever not check the math
3. This IS actually one calculation I Could check
4. I am still struggling with the concept behind what Argus has mentioned and Phil’s explanation and what is really going on . . . oh wait I think I got what Phil is saying……..ASTER covered the region from the equator to the regions at approx 83 degrees latitude both north and south which equals 99% of the Earth’s total surface area (if it were a perfect ball) and that might seem odd (i know its right there but sometimes you have to read things a couple times to get it). Yes I would think that there might be more surface area proportional to the whole than 1% from 83 – 90 degrees especially if you include both hemisphere’s but understanding the math behind it kinda makes that thought go away or drawing lines on a ball and visualizing it but the math sure makes you sleep better.

Phil said: Math! Surprising people since the time of Pythagoras.

Whether math was “knowingly” sewn into the fabric of our existence or not is not a question which is answerable to me. The fact that man has discovered some amazing equalities and relationships about that existence within our time is though. Whether philosophy or physical understanding of the world is more important, well, I argue they are one in the same.

It is sometimes better to be a dreamer than a technical genius and vice versa; though I suspect I would gladly have my rates of change in the understanding of philosophy and mathematics gradually increase to infinity together as one. I even suspect perhaps one cannot exist without the other. For the base philosophy behind even being able to count to ten by ones could be considered a magical understanding perceived through mathematical reasoning.

I must contend though that our grand understanding of mathematics cannot reach infinity faster than our grand understanding of philosophy can reach infinity ha; but then again perhaps mathematics and philosophy share a relation which cannot be expressed without using the other. Perhaps one effects the other on opposite sides of the equal sign. Perhaps there is an equation for the grand types of understanding in men.

Until then,
Great Job Humanity

Whether the Evolutionary Creation of the Universe employed mathematics to develop itself with itself or if it just sprung up as a resultant of all the hustle and bustle between matter and elements and space and time . . . I don’t think it matters folks. It is a beautiful reality to wonder is what does matter.

p.s. Iama get a Life soon

There’s something wrong with this sentence.

Should it be “both straight down and slightly behind”?

Does anyone know how big a correction to this we might need because the Earth isn’t actually a sphere? I mean, are we talking 0.75% vs 0.74% or is it a bigger error?

sin 83˚ = 0.992546

(The 99% threshold is passed just before 82˚.)