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