GLIMS Working group on algorithms

[Andreas Kaeaeb]

Dear all, sorry if you had problems with my e-mail sent yesterday, if you
recieved it at all. Problems occurred either because I sent the e-mail not
from my mail-address included in the list or due to a size limit of 0.1 KB
on the list server.

The graphic I'm talking about below can now be viewed at
http://spot.colorado.edu/~braup/glims_algor/ (Thanks, Bruce!)

Andi Kaeaeb


> Dear all
> 
> After diving a bit deeper into GLIMS and some discussions with the
> Flagstaff team I drafted a flowchart showing how the data-flow
> could work, and where and what algorithms we need. Hopefully, this
> graphic can help starting discussion. The bold rectangles are the ones of
> special interest for us. '>>> ... <<<' mark questiones where (in my
> opinion) we certainly need some discussion.
> 
> First some remarks on the chart, refering to the circled numbers:
> 
> (1) ASTER-images and orbit information submitted to RC. By the way, you
> will very soon obtain a test image. The Flagstaff team is just selecting
> the most suited one. 
> 
> (2) It will be the RC's decision whether to use the delivered orbit
> information or own precise control points for geo-registration. In the
> first case, immobile points on the image are needed for multitemporal
> comparison (for details cf. GLIMS-homepage!)
> 
> (3)&(4)&(5) For deriving ice and snow boundaries we will use three types
> of methods: 
> 
> (4) a standard multispectral classification for clean ice. This algorithm
> should be a more or less simple and uniform one for entire GLIMS,
> easily applicable for every RC. Within the Swiss Glacier Inventory we 
> (mainly the work of Frank Paul) have good experience with ratio-images and
> subsequent thresholding. 
> >>> Have you suggestiones on identifying such GLIMS standard algorithm ?
> <<<
> 
> (5) the case is more difficult for debris covered ice. The debris-covered
> ice is certainly important for a inventory. Monitoring glacier
> fluctuations from debris-covered ice, however, is a difficult thing
> anyway. So, perhaps, we need less accuracy for these cases. As you
> know, Bruce Raup did some work on detecting the debris-coverd ice boundary
> by geomorphometric DEM-analysis. 
> >>> Should we focus on this method, or have you other suggestiones ? <<<
> Michael, you have some experience with
> sophisticated multispectral classification of debris-covered ice. Others?
> 
> (3) besides the above "GLIMS-standard" algorithm, we should allow every
> group to improve such results by enhanced classification, manual or
> semi-automatic digitising, or field work, or... depending on the
> available experience and equipment. 
> >>> Shall we introduce two groups of boundaries in the GLIMS data base, a
> standard one (11) and a individually improved one (10), or simply take the
> best (RC-decision) ? <<<
> 
> (6)&(7) Software for DEM generation from the ASTER stereo channels is in
> progress here in Flagstaff. 
> >>> Anyone with special experience in this field and willing to help ? <<<
> A software for measuring ice motion is not yet started, but could be part
> of the DEM-package, using also cross-correlation techniques. 
> >>> Anyone with experience in this field and willing to help ? Other
> suggestiones than cross-correlation techniques ? <<<
> (for details cf. also GLIMS-homepage). (I'll be able to help with
> (6)&(7)).
> 
> (8) cf. GLIMS-homepage. (There is presently a discussion on the
> subdivision of contiguous ice masses and related ID-assignment. Related
> to that is a discussion whether to introduce different types of
> boundaries: distinct (e.g.ice/rock), indistinct (e.g.firn-divide) ,
> arbitrary).
> 
> (9) One thing which has to be deduced manually (or semi-automatically) is
> the (or several) central flow lines. These are of some importance for
> deriving glaciological parameters (14). 
> 
> (14) There are some (simple) algorithms needed to derive glaciological
> parameters from the above results (glacier area, altitudinal range,
> length, slope, direction etc.). I suggest, it should be a task of the
> parameter group to define these parameters and the way to compute it in a
> GLIMS standard way. Many of these parameters can be both calculated from
> the entire glacier and a flow line. For most parameters a intersection of
> the planimetric boundaries and flow lines with a DEM is necessary.         
> 
> (16) The data base things are not our task. Presently definition of
> maximum data base fields and the minimum required for data base entry is
> underway.
> 
> 
> Thanks for taking you the time to go through that all !!! Comments on
> everything are most welcome !!!
> 
> Greetings from snowy Arizona. Good skiing conditions!
> 
> Andy Kaeaeb
> 
> P.S. Bruce: Can you take Yves Arnaud ( yves.arnaud at ird.fr ) on the list.
> Thanks!
>