Elsewhere in western Greenland, the gradient of surface DEM could serve as a proxy for direction of surface ice flow but along the coast the surface topography is pocketed enough to make that unworkable at resolution -- it's better to animate Landsat to see what the ice is really doing (but see another trick for that below).
With 22 years of ice penetrating radar flights covering Greenland, these being the primary experimental data available for bedrock topography, ice depth, paleo, and deformation history, there's a need to associate ice surface velocity to radar transects. This might be utilized for anisotropic kriging (bedrock smoothed in flow direction), modeling of future flow, or direction of fold developmentin temperate ice.
Flightlines are represented by Cresis as a few dozen high precision lat,lon waystations per 50 km flight segment in kml format (a rigidly formatted txt file carrying a small metadatabase). Needless to say, when the plane changed course, it flew a smooth curve rather than abruptly changing bearing at the joints in line segments defined by the waystations.
Kml files open in the convenient rescalable vector GIS view of the flight in Google Earth. GE also carries with it a Greenland surface DEM of unknown quality relative to what Greenland glaciologists use. GE can plot the slope along any selected portion of the flightline but has no export capability (other than a screenshot, which can be csv'ed in ImageJ).
That's unfortunate as it could have been added across the Cresis data archive. The problem there is that the z coordinate was to zero in all Cresis tracks. Work-arounds can be found using Google search that output the elevations as a csv excel file, eg
http://www.geocontext.org/publ/2010/04/profiler/en/ or
http://www.gpsvisualizer.com/convert_input or
http://freegeographytools.com/2010/online-elevation-profilerThe gradient map of a high quality Greenland surface (or bedrock) DEM could be brought into Google Earth as an image overlay but what is needed is a companion track to each flight line that shows a velocity vector coming off each waystation.
This is not hard to do since for a given waypoint lat,lon it is only necessary to look up the velocity there to get the second point of the new 'path'. It's unfortunate that kml doesn't allow for display of extra vectors. (At some point, ArcGIS or similar proprietary software starts to make more sense.)
The images below show the surface of a deformation region inland from Eqip that is covered by the new Sentinel velocity map in the previous post (which is in polar stereographic rather than GE projection: dgal needed). The purple flight lines come in from the calving front -- there are 4-5 repeat flights from different years because the Operation Icebridge navigator followed a perceived centerline of glacier flow.
The third image shows one of these from 2013, again seeming to spill over into an along-flow bowl. It appears the physical context of this upheaval was grievously mischaracterized in an earlier publication. There are 35 radar tomographic transects of this upheaval dating from 1995 to 2014 that must be evaluated, along with 56 Landsat-8 cloud-free scenes from 2013-15 to determine local ice surface velocity flow and presence of meltlakes, moulins and streams overhead.
