Celestia Forums

Posted: **30.06.2009, 17:25**

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Posted: **30.06.2009, 17:54**

I was about to post this link, but you beat me too it... Looks like we can finally fill in those high latitude regions. The new data is complete between 83 degrees north and south.

--Chris

Posted: **30.06.2009, 18:20**

john Van Vliet wrote:http://www.gdem.aster.ersdac.or.jp/
http://www.ersdac.or.jp/GDEM/E/index.html

These links are dead.

Posted: **30.06.2009, 19:02**

chris wrote:I was about to post this link, but you beat me too it... Looks like we can finally fill in those high latitude regions. The new data is complete between 83 degrees north and south.

--Chris

Well it wasn't all that bad before: between 60 and 90 degrees north, we used the

30 arc-second GTOPO30 dataset [USGS, 1996],

while in the southern hemisphere from 90S..60S, we used the

RAMP II dataset (Radarsat Antarctic Mapping Project Digital Elevation
Model Version 2, [Liu et al., 2001]).

How good the new data really are (and how well they match up with the BMNG base texture), will require careful examination. Also the published format will be quite important.

Fridger

Posted: **01.07.2009, 20:48**

t00fri wrote:How good the new data really are (and how well they match up with the BMNG base texture), will require careful examination. Also the published format will be quite important.

Your caution about the new data set appears to be well-founded. This review points out some that some serious artifacts exist in the new elevation data:

http://www.viewfinderpanoramas.org/reviews.html#aster

From the documentation:

* While the elevation postings in the ASTER GDEM are at 1 arcsecond, or approximately 30 m, the detail of topographic expression resolvable in the ASTER GDEM appears to be between 100 m and 120 m.
* Much more troublesome than residual cloud anomalies, however, are a variety of pervasive artifacts that are clearly related to linear and curvilinear boundaries between different stack number areas. Such artifacts appear as straight lines, pits, bumps, mole runs, and other geometric shapes. Anomalous elevations associated with these artifacts can range from 1 m or 2 m to more than 100 m.
* The existence of most water bodies is not indicated.

--Chris

Posted: **01.07.2009, 21:45**

Thanks Chris for the docs,

that indeed doesn't look all that promising. Notably these pervasive artifacts that are related to linear and curvilinear boundaries between different stack number areas sound pretty nasty and hard to remove.

As soon as I got some spare time, I'll have a careful look at these new data.

Fridger

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