Proposal for RC --> NSIDC data transfer methodology: Rev. 1.11

[Bruce Raup]

Luke,

Thanks for the comments.

On 2001-10-01 15:17 -0600,  Luke Copland wrote:

> 1. Is it worthwhile being able to transfer images in geotiff (*.tif)
> format? These images are georeferenced, so it would make it easier to
> relate them back to the shape files than using non-georeferenced jpg/gif
> imagery. I'm not sure if it would be feasible to store the files as
> .tifs, but convert them to jpg/gifs when requested for viewing on a web
> browser?

I think this is a good idea for satellite or aerial images.  (For images
taken from the ground, JPEG or PNG should do.)  I don't know of a
command-line GeoTIFF to jpg converter, but I'm guessing one can be found.
I'll look into it.  I did notice that the open-source GIS program "GRASS"
will import and export GeoTIFF files.  By the way, GRASS also will read and
write ESRI shapefiles.

References:
http://www.remotesensing.org/geotiff/geotiff.html
http://www.baylor.edu/grass/

> 2. Are you still planning on differentiating between areas of a glacier
> boundary which are delineated by rock versus those defined by an ice
> divide? If so, what are the terms that should be used in the attribute
> table?

Yes.  We need to finalize these lists of valids.  We hope to post a straw
man version to this list soon.

> 3. Can elevation datasets be stored in the database if they are
> available? If so, then in what format? I'm guessing that TSV files could
> work, or perhaps geotiffs (which is the format we mainly use here to
> transfer elevation information).

The Point_Measurements table can hold small datasets.  We've talked a bit
about how (and whether) to handle large elevation grids, but haven't come
to a conclusion.  GeoTIFF files would probably work for that.  I wonder
what the volume of such data would be.

Just a reminder:  The latest information on the database design is at
http://spot.colorado.edu/~braup/glims_database/
I will update the information on the main GLIMS site soon.

> We're tending towards the idea of working upwards from a glacier
> terminus, and counting all tributaries that feed ice and water into the
> terminus as part of one single glacier.

Sounds reasonable.  Does ArcView do this delineation for you automatically?
Or have you written Avenue scripts to do it?

> I'm currently working on defining and cataloguing the glaciers on Manson
> Ice Cap, Ellesmere Island, as a way to work through potential problems
> and to demonstrate our methods to others. Once done, I'll send on the
> information to NSIDC so that it can be input to the database and any
> issues can be identified.

This is exactly what we were hoping for!  We would appreciate other groups
who are at a similar stage to do likewise.

Siri Jodha and I just chatted and realized we interpreted your last
sentence slightly differently.  By "issues", do you mean with the data
transfer method?  Or were you talking about issues with the definition of
"glacier"?  (I assume you meant the former.)

Thanks,
Bruce

-- 
Bruce Raup
National Snow and Ice Data Center                     Phone:  303-492-8814
University of Colorado, 449 UCB                       Fax:    303-492-2468
Boulder, CO  80309-0449                                    braup at nsidc.org