Hi All, Thanks for the responses on the additional database fields. We could add the following fields to the Glacier_Dynamic table (exact names to be determined): primary_classification2 frontal_characteristics2 tongue_activity2 (same valids as corresponding primary fields) debris_cover nil, low, moderate, heavy, thin debris_distribution medial moraines, patchy, terminus cover I like Jeff's proposed valids for the "debris" fields. I thought at first that a simple numerical value indicating percent of debris cover might be better, but upon reflection, it seems that a few simple categories will be easier to search on, and are appropriately qualitative. If someone wants quantitative debris data, they could, in theory, go to the debris "segments", if they're there, and calculate the percent cover. --Bruce On 2003-02-27 08:49 -0700, Jeffrey S Kargel wrote:
1. Is it sufficient to add extra fields for just the three listed above?
I see that there is no place, other than in a comment, to indicate something about debris cover. Possibly in "longitudinal characteristics" there could be an entry for "debris cover abundance," with possible valids being nil (estimated <1% ice-free pixels below snowline, low (estimated ice-free cover 1-10% of pixels below snowline), moderate (10-50% ice-free pixels below snow line), heavy (50-100% ice-free pixels below snowline), and thin (debris cover may be widespread but few pixels are ice-free below the snowline-- there is dominantly subpixel mixing of debris and ice). There could also be an indication of the qualitative "distribution of debris," with up to 2 valids, including: medial moraines, patchy (as from landslides for example, i.e., lacking medial moraine type structure), terminus cover.
2. Is it sufficient to add only one extra field to each (so that a given glacier could have two "primary_classification"s at one point in time)?
For simplicity, I think 2 is enough. There will be instances where people really want more than 2, but I think those will be few.
I am replying to the whole list, since my suggestion under #1 may require some broad discussion. I also think that before the final stamp of approval is placed on the revised database structure and valids definition (but after the DB WG has had their say in this new round of revision), perhaps it should be opened to comment from the entire GLIMS group. Judging from the small response to some related emailings and solicitations of data, there may need to be another hand-holding e-tutorial on how to access the database structure and definitions, and how to input data, plus a pretty stern resolicitation of data for the database. People have simply got to get into the database. There may need to be a individualized communications with some RCs, and I would be happy to do my part in that if needed.
--Jeff K
On 2003-03-03 13:31 -0700, Luke Copland wrote:
Hi Bruce,
I agree with your proposal to allow more than one value for the following fields:
primary_classification frontal_characteristics tongue_activity
...as we discussed at Chamonix, it's often impossible to place a glacier into only one classification. Saying this, we should only need to have two valids for each field to cover most eventualities.
One other field that you might think about allowing two classifications for is the 'Tongue_act' - this is so that surge glaciers can be properly described. This is to allow for the fact that (e.g.) we might know that a glacier is surge-type (i.e., category 7), but when it's not in its active phase the terminus might be retreating or advancing (i.e., any of categories 1 to 5).
It would be of major help when putting together the database to have a detailed description (and example imagery) of the permitted valids for each of the classifications. Fabian Munz showed an example of this in Chamonix, so I was wondering if you've had any chance to follow up on it. I've put together my own description of valids (see attached) based largely on the following book (although this doesn't cover any of the proposed new categories for debris cover, etc.):
Armstrong, T., Roberts, B. and Swithinbank, C. 1973. Illustrated Glossary of Snow and Ice. Cambridge, Scott Polar Research Institute Special Publication No. 4.
And finally, I like Jeff's suggestion of adding a descriptor for debris cover. The valids he suggests seems reasonable, and it would be useful to be able to include this information in the database.
Cheers, Luke.
P.S. Feel free to copy this email to the general GLIMS distribution list as you see fit.
-- Bruce Raup Phone: 303-492-8814 National Snow and Ice Data Center, U. of Colorado, 449 UCB, Boulder, CO 80309