Researcher requires geographical subset due to disk space restriction. Goes directly to NSIDC site hoping for “one stop shopping” at Overall strategy is to obtain long time series of topographic variations preferably from high level products to avoid involved processing by researcher. Strategy: Step #1) First need to ascertain Dome C coordinates; Google search “Dome C, Antarctica” inside nsidc.org Took some searching to find following title search containing coordinates within abstract Antarctic ice core locations − Labels the locations of three well-known deep ice cores from the Antarctic ice sheet, including: the European Project for Ice Coring in Antarctica (EPICA) Dome C core (75°06'S, 123°21'E) Google www search (accessed within nsidc.org) proved to be quicker 1 st attempt: – interesting facts but no coordinates 2 nd attempt: The latitude of Dome C is 75° 06'S, the longitude 123° 23'E. (map from frequently asked question #14 about Dome C !) Ice Sheet Elevation NSIDC User Scenario: Access topography data over Dome C, Antarctica

Strategy Step #2) Browse NSIDC site first for higher level DEM product. Geographical sub- setting capability would be a plus : accessed from pull down menu “Quick Links to Data Collections” directly in center of main page; very convenient: proceed to DEM data summaries link to ftp://sidads.colorado.edu/pub/DATASETS/DEM/nsidc0304_icesat_antarctic_dem/ “This DEM is generated from the first seven operational periods (from February 2003 through June 2005) of the GLAS instrument. It is provided on polar stereographic grids at 500 m grid spacing. The grid covers all of Antarctica north of 86° S.” All I need is topography over Dome C; no geographical sub-setting. Have to download entire Antarctic grid. Bypass Optional Registration allows me to see data set size ( Kb (500m), 5981 Kb (1Km resolution)). Would of liked to see tool to plot time series of DEM topography at user specified lat/lon coordinates. However the following link provides useful Unix command to interpret grid array enabling extraction of Dome C regional subset. Strategy Step #3) The IceSat DEMs only span from Feb 2003 – June Need to extend time series by accessing more recent data. Go directly to fromhttp://nsidc.org/data/icesat/ Related Data Collection, then to Data Summaries at Which provides table of data processing levels; link to (GLAS/ICESat L2 Antarctic and Greenland Ice Sheet Altimetry Data). Go directly to data ordering info hoping again for sub-setting capability ; table provides link to Subsetting is available for select ICESat/GLAS data products leads to data order form Simply enter lat/lon coordinates and select data product (GLA12 in this case) and submit ftp://sidads.colorado.edu/pub/DATASETS/icesat/tools/idl/reader/ngat/

Strategy Step #3) Downloaded GLAS/ICESat DEMs (Feb 2003 – June 2005) and have ordered latest ICESat altimetry to extend time series. Also need topographic “benchmark” from historical record: Return to DEM data summaries link Radarsat Antarctic Mapping Project Digital Elevation Model Version 2 provides DEMs at 1 km, 400 m, and 200 m resolution. Data were collected between the 1940s and present, with most collected during the 1980s and 1990s.Documentation link provides DEM sample data output (always comforting when you can verify your read software is delivering correct values), and direct links to references providing info on derivation techniques and algorithms, error handling, and accuracy for DEMs based on multiple data types. Procedures for obtaining data at ftp://sidads.colorado.edu/pub/DATASETS/RAMP/DEM_V2/ allows bypass directly to data to allow me to browse data size of 1km binary DEM (14245 Kb) and ASCII ( Kb). ftp://sidads.colorado.edu/pub/DATASETS/RAMP/DEM_V2/ Overall Experience: Starting at Quick Links pull down menu on main page I was able to navigate easily to higher level DEMs directly to obtain a recent times series derived from GLAS/ICESat and earlier observations from Radarsat Antarctica Mapping Project (RAMP), as well as subset a manageable sized ICESat altimetry data set to extend DEM time series in much less than the obligated 2 hours spent. Always appreciate when cited references have links. Often this is not the case on NSIDC site. A simple widget type browser to observe DEM topographic time series at specified grid locations would be a useful enhancement.