Support the Arctic Sea Ice Forum and Blog

Author Topic: Jakobshavn Isbræ / Ilulissat Isfjord / West Greenland  (Read 575413 times)

A-Team

  • ASIF Upper Class
  • Posts: 1914
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #600 on: February 26, 2015, 08:27:30 PM »
Annual advance advocates anxiously anticipating an apparently arresting accident: could this be the start of next big thing?

The orange arrows possibly point to a widening crevasse that may become the next calving front.

sidd

  • ASIF Upper Class
  • Posts: 1710
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #601 on: February 27, 2015, 07:23:33 AM »
heres sumpn the right way up ... sorry for the delay

A-Team

  • ASIF Upper Class
  • Posts: 1914
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #602 on: February 27, 2015, 11:35:49 AM »
Nice, sidd. Below, I colored up at 6x vertical exaggeration the underlying grayscale for that data (big help here from Jim H and sidd over at the developer's corner forum http://forum.arctic-sea-ice.net/index.php/topic,1165.0.html)

This brings out the troughs and sills in a different way but perhaps most interestingly the old channels and confluences farther back upstream. The second image (taken from Morlighem's home page) shows the broader context of the presumed paleo drainage system -- we don't as yet have this bumped up to native bedrock horizontal resolution (which is 150 m posted, 400 m experimental).

The Jakobshavn fast ice stream today seems to be coming preferentially from northern channel rather than the formerly important easterly two channels, though this is not so evident from surface features, meaning the relative contribution have to be taken from surface velocity maps. I've not seen any explanation for this.
« Last Edit: February 27, 2015, 12:19:19 PM by A-Team »

A-Team

  • ASIF Upper Class
  • Posts: 1914
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #603 on: February 27, 2015, 12:38:03 PM »
Here are those upstream velocities from the main source of these, Joughin 2010. I'm recalling that many moons ago an update of these was posted in this forum from a UW disseration. We also know from AG2014 that T Scambos is readying a paper refining the slow velocity map using the newly available pairs 16-bit resolution of Landsat8.

This is easy enough to do ourselves with standard-issue ImageJ2 plugins. With a year separating the 2014-15 images and 15 m resolution, it should be feasible to map the velocity almost to the summit ridge. More ambitiously, Howat has posted 2 m DEMs from worldview 0.6 m pairs but it's not clear that really slow velocities can be pulled from this produce.

The 15 m is more than enough to quantitatively resolve the extent of ice stream confinement to paleo channels. Ice from the sides is also contributing and at elevation will swamp out the channelized flow.

Looks like the 8,11 path rows go the farthest inland for Landshot scenes. The 21 Feb 15 is very clear, about 11º sun angle. There are six cloud-free images with the 'same' geometry from 2014 and one even from 2013, so this should be a snap using bUnwarpJ to get the velocity vector field by image pair feature correlation as at http://forum.arctic-sea-ice.net/index.php/topic,400.msg41367.html#msg41367

LC8008011 2015 052 LGN00 2015-Feb-21  Sun Elevation = 11.04
LC8008011 2014 305 LGN00 2014-Nov-01  Sun Elevation = 05.99
LC8008011 2014 273 LGN00 2014-Sep-14  Sun Elevation = 17.58
LC8008011 2014 209 LGN00 2014-Jul-28  Sun Elevation = 39.29
LC8008011 2014 193 LGN01 2014-Jul-17  Sun Elevation = 42.31
LC8008011 2014 161 LGN00 2014-Jun-10  Sun Elevation = 43.48
LC8008011 2014 081 LGN00 2014-Mar-22  Sun Elevation = 21.16
LC8008011 2013 270 LGN00 2013-Sep-27  Sun Elevation = 18.66
« Last Edit: February 28, 2015, 01:35:52 PM by A-Team »

A-Team

  • ASIF Upper Class
  • Posts: 1914
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #604 on: February 27, 2015, 06:44:42 PM »
Here's a contour map of the depths of Jakobshavn main channel generated by the incredible French online tool G'MIC (https://gmicol.greyc.fr/) from the bedrock DEM kindly provided by Jim Hunt, followed by a steepness map (norm of gradient) of the side walls.

A-Team

  • ASIF Upper Class
  • Posts: 1914
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #605 on: February 28, 2015, 03:30:41 PM »
The images below take a look at the Jakobshavn paleo confluence with a view towards determining whether upstream fast ice flow today follows the three channels in proportion to their depth.

The first image gives a sense of how intensively Jakobshavn has been sampled by ice penetrating radar (very). The second shows that even slightly past the confluence (67 km from the calving front) that radar is still having great difficulty determining depth bedrock.

The third locates the confluence on 21 Feb 15 Landsat (pink dot) where it is arguably recognizable for some distance on the surface, with the northern fork most prominent, even though it is not the most excavated. The fourth shows bedrock topograpy as refined by Morlighem with the confluence contoured.

Espen

  • ASIF Governor
  • Posts: 3078
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #606 on: February 28, 2015, 09:03:22 PM »
Not reporting another trivial calving this time, but watch the speed of Jakobshavn over 9 days:
Have a ice day!

A-Team

  • ASIF Upper Class
  • Posts: 1914
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #607 on: March 01, 2015, 11:31:29 AM »
Looking at the distance moved across a transect 5 km upstream of the calving front between 12-28 Feb 15, velocities are moderate by JI summer standards, averaging 23.1 m/day or 8.4 km/yr but with peak speed of 9.3 km/yr which is quite high for February but seeming below the all-time record set in February of 2013.

The error is rather fragile because one pixel off makes a difference at the level of 15 m B8 Landsat channels (which has been bumped up to 10 m here) but the speed is consistently higher in the center of the channel, falling off to the sides as expected from resistance from the wall bedrock.

Since the trough and sill situation is not centered whereas speed is, bedrock topography is not explicitly controlling. However the position of the calving front with respect to this topography does matter, as would timing relative to major calving events.

This transect corresponds, more or less, to the M9 station in Fig.2 of Joughin 2014 www.the-cryosphere.net/8/209/2014 below. However a real comparison can only be done by replicating their internal system of measurement which is not feasible.
« Last Edit: March 01, 2015, 11:58:20 AM by A-Team »

Espen

  • ASIF Governor
  • Posts: 3078
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #608 on: March 01, 2015, 11:39:30 AM »
Looking at the distance moved across a transect 5 km upstream of the calving front between 12-28 Feb 15, velocities are moderate by JI standards, averaging 23.1 m/day or 8.4 km/yr but with peak speed of 9.3 km/yr which is quite high for February but seeming below the all-time record set in February of 2013.

This transect corresponds, more or less, to the M9 station in Fig.2 of Joughin 2014 www.the-cryosphere.net/8/209/2014 below. However a real comparison can only be done by replicating their internal system of measurement which is not feasible.

A-Team can you the same measurements with the updated images from Wipneus over at the Zachariae section, the thing is really moving at the moment?
https://forum.arctic-sea-ice.net/index.php/topic,400.msg46355.html#msg46355
Have a ice day!

A-Team

  • ASIF Upper Class
  • Posts: 1914
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #609 on: March 01, 2015, 10:49:15 PM »
Wipneus is set up to do that for Sentinel. Landsat is not up that far north yet. There is more involved than just determining the velocity vector field ... there is the question of how it compares to earlier years. For that, I would recommend Fig.S13 of the supplemental of Shfaqat Khan 2014 which has a very thorough treatment, free at http://www.nature.com/nclimate/journal/v4/n4/extref/nclimate2161-s1.pdf

Zachariae is another case of the tail wagging the dog -- relief of buttressing at the marine terminus is what it takes to get the 600 km long ice stream moving, with melt lakes and lubrication playing less of at role at 79º north (but see attached 2014 melt lake on Petermann) and the relevancy of nearby basal ice upheavals not understood. For now, that acceleration has not propagated very far from the coast.

It's good to remember that the overwhelming bulk of ice volume in Greenland lies above the Parca stake line at 2000 m  so not much will happen to sea level rise until serious ice starts going through the flux gates.

Rubikscube

  • ASIF Citizen
  • Posts: 247
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #610 on: March 07, 2015, 10:42:02 PM »
What is to be made of the very large overdeepening to the south east of JI running in almost opposite direction of the other channels in the JI paleo drainage system? It seems a bit misplaced.
« Last Edit: March 08, 2015, 03:10:13 AM by Rubikscube »

solartim27

  • ASIF Citizen
  • Posts: 438
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #611 on: March 17, 2015, 06:17:48 PM »
Not reporting another trivial calving this time, but watch the speed of Jakobshavn over 9 days:

Does not seem to have slowed down any.  Click to animate.
FNORD

Espen

  • ASIF Governor
  • Posts: 3078
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #612 on: March 19, 2015, 11:11:54 PM »
Lets not forget the facts, see what I read in the newspaper today:
Have a ice day!

Sleepy

  • Guest
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #613 on: March 20, 2015, 07:01:20 AM »
Nice one Espen. Just wondering about the date, when will it be possible to pass between Helheim and Jakobshavn again? I thought I'd add a smiley there but it got stuck...  :-\

Sleepy

  • Guest
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #614 on: March 21, 2015, 05:58:30 AM »
This one's for sale. ;) Only 295€...



"Oerter welche wegen der schwimmenden oder festen Eisberge unbeschifbar sind."

Carex

  • ASIF Lurker
  • Posts: 38
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #615 on: March 29, 2015, 03:51:08 PM »
That straight is almost completely visible on yesterdays MODIS.    I'm a bit illiterate when it comes to posts but I imagine most of you view MODIS regularly.

Carex

  • ASIF Lurker
  • Posts: 38
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #616 on: March 30, 2015, 12:51:37 PM »
Actually, can anyone educate me about the nature of this nearly linear feature that shows up on the 3/28 MODIS image from the mouth of Jakobshavn nearly to the height of land?? And corresponds quite well with the old straight??

Carex

  • ASIF Lurker
  • Posts: 38
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #617 on: March 30, 2015, 01:28:14 PM »
Let me see if I can actually attach the picture.

Laurent

  • ASIF Governor
  • Posts: 2525
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #618 on: March 30, 2015, 02:15:09 PM »
Do not panic when you see this kind of thing, wait an other set of picture and see if it is still there :
https://earthdata.nasa.gov/labs/worldview/?p=arctic&l=MODIS_Aqua_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor,Reference_Labels(hidden),Reference_Features(hidden),Coastlines&t=2015-03-29&v=-249655.5089700388,-2354306.117151937,-85815.50897003879,-2238978.117151937

Doesn't seem to be there the 29th...
Probably a cloud !
May be you are talking of something else...be more precise then.

Carex

  • ASIF Lurker
  • Posts: 38
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #619 on: March 30, 2015, 03:50:21 PM »
Details,  Beginning withing a few kilometers of the outlet of Jakobshavn there is a near linear features running very close to SE for 75% to 80% of the distance across the island.  The feature is somewhat irregular in the lower, faster moving sections, from there it becomes quite liner and narrow for a considerable distance. When the feature reaches the upper elevations of the ice cap it becomes less liner and more variable in width.  As it approaches an area of apparent irregular topography influenced by bedrock (or an area of clouds?) it appears to widen slightly into a fan shape, opening toward the high ground. Just east of this, assumed, high ground the feature may be seen again, slightly offset but still bearing SE. The feature fades before bedrock influenced topography is apparent, nearing the east coast. 
Conditions appear to be quite clear as surface details are discernible both SE and NW of the feature.  A vapor trail perhaps?  This should be checkable.  Conditions on the 29th are much cloudier, especially to the east.  I saw this and headed to the forum to ask about it and was greated by those two old maps, very apropo.  The feature is obvious at all pixel sizes from 4K to 250m.  It looks like a giant slump.

Espen

  • ASIF Governor
  • Posts: 3078
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #620 on: April 02, 2015, 08:56:59 AM »
Jakobshavn Isbræ update, as can be watched in animation below, Jakobshavn continuous its "self-destruction":
Have a ice day!

Espen

  • ASIF Governor
  • Posts: 3078
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #621 on: April 02, 2015, 10:34:39 AM »
But far away from the max. retreat set September 28 2014:
Have a ice day!

Iceismylife

  • ASIF Citizen
  • Posts: 182
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #622 on: April 14, 2015, 11:30:26 PM »
A possible explanation for the shallower northern arm of the confluence to be speeding up more than the others is that it is narrower and confines the melt water at its base more.  Also being narrower its base would have experienced more heating when the flow started accelerating, leading it to provide more of the flow to the main channel.

Iceismylife

  • ASIF Citizen
  • Posts: 182
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #623 on: April 15, 2015, 09:02:33 PM »
...
 Is it just too far into the future?
That is the question I've been looking for an answer to.  Assuming the calving face keep retreating at its current rate how long until it gets there?

My read is we are on an exponential growth curve in ice flow. 2X every 5 years.

Espen

  • ASIF Governor
  • Posts: 3078
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #624 on: May 13, 2015, 05:55:38 AM »
Jakobshavn Issbræ the calving-machine is up in gear again:
Have a ice day!

Yuha

  • ASIF Citizen
  • Posts: 207
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #625 on: May 13, 2015, 11:37:52 PM »
Jakobshavn Issbræ the calving-machine is up in gear again:

The calving was likely triggered by an unplugging of the fjord:

Espen

  • ASIF Governor
  • Posts: 3078
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #626 on: May 14, 2015, 07:17:48 AM »
Updated version:
Have a ice day!

Espen

  • ASIF Governor
  • Posts: 3078
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #627 on: May 16, 2015, 04:48:53 PM »
Latest High-Resolution Landsat image from May 12 2015:
Have a ice day!

Espen

  • ASIF Governor
  • Posts: 3078
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #628 on: May 16, 2015, 11:10:18 PM »
The calving front at Jakobshavn is very different to September 28 2014 (record retreat), not only did the glacier expand since then but the front is much narrower?
Have a ice day!

Jim Hunt

  • ASIF Governor
  • Posts: 3306
    • View Profile
    • The Arctic sea ice Great White Con
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #629 on: May 16, 2015, 11:51:52 PM »
The front is much narrower?

It looks that way to me as well. I've taken the liberty of republishing your animations over at:

http://GreatWhiteCon.info/2015/05/jakobshavn-isbrae-calves-yet-again/

I hope that's OK with you? Please let me know ASAP if not.
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Espen

  • ASIF Governor
  • Posts: 3078
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #630 on: May 17, 2015, 10:30:36 AM »
The front is much narrower?

It looks that way to me as well. I've taken the liberty of republishing your animations over at:

http://GreatWhiteCon.info/2015/05/jakobshavn-isbrae-calves-yet-again/

I hope that's OK with you? Please let me know ASAP if not.

Hello Jim, that is ok with me, thanks! :) :)
Have a ice day!

tpelte

  • ASIF Lurker
  • Posts: 2
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #631 on: May 19, 2015, 02:55:51 PM »
Huge calving seemed to occur between last sentinel pictures (17 / 18).  Can anyone confirm this with  other satellite pictures ?

Espen

  • ASIF Governor
  • Posts: 3078
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #632 on: May 19, 2015, 04:32:04 PM »
Hello tpelte,

When I compare the images, it looks like the glacier expanded?
Have a ice day!

tpelte

  • ASIF Lurker
  • Posts: 2
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #633 on: May 19, 2015, 05:13:59 PM »
I guess I get confused by shadows and brightness of ice at some places.  Sorry for that false alarm.  Thanks for the tremendous work you're doing here.

Lennart van der Linde

  • ASIF Middle Class
  • Posts: 697
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #634 on: May 20, 2015, 10:12:16 PM »
Recent lecture by Richard Alley, including remarks on Pollard et al 2015 and Applegate et al 2014 on potentially very fast ice loss from WAIS and GIS, with examples of cliff failure from Jakobshavn:


Thanks to Colorado Bob for posting this over at the ASIB.

Bernard

  • ASIF Lurker
  • Posts: 31
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #635 on: May 26, 2015, 10:52:16 PM »
Dear all

Completely puzzled by the aspect of the calving front of Jakobshavn Isbræ in today's view at
http://rapidfire.sci.gsfc.nasa.gov/imagery/subsets/?subset=Arctic_r02c02.2015146.terra.250m.
Looks completely different, as if some catastrophic calving or surge had happened.
How do you folks read this image?

solartim27

  • ASIF Citizen
  • Posts: 438
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #636 on: May 26, 2015, 11:01:17 PM »
I believe it is just a cloud.  The radar images are nice to get below that stuff, though it is cut off so far today:
http://www.polarview.aq/arctic
http://ocean.dmi.dk/arctic/disko.uk.php
FNORD

Jim Hunt

  • ASIF Governor
  • Posts: 3306
    • View Profile
    • The Arctic sea ice Great White Con
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #637 on: May 26, 2015, 11:09:32 PM »
How do you folks read this image?

Try flipping between Aqua & Terra on Worldview:

http://1.usa.gov/1AskSpn

Looks like a cloud to me.
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Bernard

  • ASIF Lurker
  • Posts: 31
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #638 on: May 27, 2015, 11:06:25 PM »
Thanks! Cloud indeed ... back to "normal" today.

nukefix

  • ASIF Citizen
  • Posts: 407
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #639 on: May 29, 2015, 12:20:53 PM »
S-1 IW HH-polarization on 27.5.2015

Yuha

  • ASIF Citizen
  • Posts: 207
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #640 on: May 29, 2015, 03:21:32 PM »
S-1 IW HH-polarization on 27.5.2015

Taken maybe just moments before a significant calving took place.

Espen

  • ASIF Governor
  • Posts: 3078
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #641 on: May 29, 2015, 05:35:32 PM »
A large calving happened between May 26 and May 28 2015:

Have a ice day!

Espen

  • ASIF Governor
  • Posts: 3078
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #642 on: May 30, 2015, 09:13:24 AM »
The same calving seen from a Sentinel sensor:
Have a ice day!

Espen

  • ASIF Governor
  • Posts: 3078
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #643 on: May 30, 2015, 11:19:59 AM »
A new large calving will come soon (red line), can also be observed in the animation above:
Have a ice day!

nukefix

  • ASIF Citizen
  • Posts: 407
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #644 on: May 30, 2015, 11:48:32 AM »
Great Espen! BTW your SAR images have very high contrast, have you experimented with taking a logarithm (or alternatively a square root) of the SAR intensity as it is more pleasing to the human eye?

Espen

  • ASIF Governor
  • Posts: 3078
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #645 on: May 30, 2015, 11:53:51 AM »
Great Espen! BTW your SAR images have very high contrast, have you experimented with taking a logarithm (or alternatively a square root) of the SAR intensity as it is more pleasing to the human eye?

Hello Nukefix,

I am using a filter in Photoshop called Camera Raw Filter and set at auto, I might need some more experience?
« Last Edit: May 30, 2015, 12:10:30 PM by Espen »
Have a ice day!

nukefix

  • ASIF Citizen
  • Posts: 407
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #646 on: May 30, 2015, 12:13:55 PM »
The S-1 SAR-data in the image-files are in amplitude-format, while the "industry-standard" is log_intensity. You can convert amplitude to log-intensity in the following way:

log_intensity = log10(amplitude^2)

This should bring out much more detail for the human eye and you can apply the Photoshop filters afterwards.

Espen

  • ASIF Governor
  • Posts: 3078
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #647 on: May 30, 2015, 12:28:35 PM »
The S-1 SAR-data in the image-files are in amplitude-format, while the "industry-standard" is log_intensity. You can convert amplitude to log-intensity in the following way:

log_intensity = log10(amplitude^2)

This should bring out much more detail for the human eye and you can apply the Photoshop filters afterwards.

Have not a clue what you are writing about, is it possible to code in Photoshop?
Have a ice day!

nukefix

  • ASIF Citizen
  • Posts: 407
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #648 on: May 31, 2015, 07:10:53 AM »
The S-1 SAR-data in the image-files are in amplitude-format, while the "industry-standard" is log_intensity. You can convert amplitude to log-intensity in the following way:

log_intensity = log10(amplitude^2)

This should bring out much more detail for the human eye and you can apply the Photoshop filters afterwards.
Have not a clue what you are writing about, is it possible to code in Photoshop?
I don't know Photoshop but I would imagine there's a plugin that allows for that?

Espen

  • ASIF Governor
  • Posts: 3078
    • View Profile
Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #649 on: June 02, 2015, 06:16:16 AM »
I have some difficulties interpreting the Sentinel images from June 1, maybe Wipneus can help?
I know there were some calving activities lately.
Have a ice day!