Recent imagery from the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument shows condensation trails over Alaska’s eastern Interior and over the eastern Brooks Range.
A condensation trail, or “contrail,” is a thin cloud left behind when the ambient humidity and temperature of the air allows the water vapor in an aircraft’s exhaust to condense and form a cloud. Some contrails dissipate rather quickly, while others may linger and even spread out over time, again all depending on the conditions of the ambient atmosphere.
This particular case is from the afternoon of Friday, October 7, and shows the true colors the human eye would see if we had hitched a ride on the satellite. Note the corkscrew contrails over the eastern Interior, and the more linear contrails over the eastern Brooks Range. At this time of year in northern Alaska the sun hangs low over the southern horizon during the afternoon, and shadows from the contrails can be seen on the ground below, offset slightly to the north.
Eielson Air Force Base’s “Red Flag-Alaska” exercise kicked off on October 6th, so these contrails appearing the following day may be associated with those activities. Contrails from civilian aircraft tend to appear more linear than the wide looping tracks evident in this imagery.
More information about the VIIRS instrument is available at http://ncc.nesdis.noaa.gov/VIIRS/ More information about Red Flag-Alaska is available at http://www.eielson.af.mil/Info/REDFLAG-Alaska.aspx
A massive new DEM data set for Alaska from our colleagues at the University of Minnesota was released On September 1, 2016. A great collaboration among academia, the National Science Foundation, and the National Geospatial-Intelligence Agency.
We recently put together a prototype time enabled Web Mapping Service (WMS) with data from MODIS and VIIRS from 2015 to mid July 2016, and as an experiment, generated a short time lapse from it. The data in this video is a false color presentation using VIIRS “I” bands 3,2, and 1, a band combination we call “Landcover”. The video spans January 2015 to July 2016, and has some interesting natural processes in it - check out the ice movement, and the spring snow melt process. The affect the seasons have on the sensor’s coverage is also visible as the visible bands of VIIRS are only active over areas of the earth illuminated by the sun.
The above animation of VIIRS polar satellite imagery over interior Alaska south of the Brooks Range from the afternoon of 15 Jul 2016, shows how quickly
fires can spread in less then 4 hours. The three images used for this
animation were modified versions of the NaturalColor RGB, where the 2.3
um channel was assigned to the red color component (rather than 1.6 um),
0.86 um to green, and 0.64 um to blue. The 2.3 um has
similar ice and snow absorption characteristics as the 1.6 um, but with
more sensitivity to hot spots and fires. In this imagery the
red pixels are the hottest and most active fires with bluish colored
smoke blown eastward by strong west winds.
We recently had a question about getting GINA’s Best Data Layer (BDL) into BackCountry Navigator TOPO GPS
a navigation and topographic map viewing application for Android
smart phones and tablets. Since it is easy to do, and might be of interest to the wider
community, here is how to do it:
First, hit the
“Map Layers” button, then the “MORE MAP SOURCES”, followed by the
“CUSTOM MAP SOURCE”, and finally the “NEW CUSTOM MAP SOURCE” menu items.
This could give you a dialog like this:
Fill it out like above, hit “SAVE”, and it should now show up in the
“Map Sources” list, and should be usable just like any other map source
in Backcountry Navigator, including using its tools for building an
More detailed instructions can be found on Backcountry Navigator’s help site.
Other mapping applications that allow custom map sources work similarly, and this process will work for any of GINA’s other web mapping tile sets.
PS: The “Max Zoom” setting affects resolution of the data - larger zoom levels mean more detail, but that comes at the cost of space. A value of 16 works out to be about 2.4 meters per pixel, 19 to be 1/3 of a meter per pixel.
New elevation color-relief hill shade layers.
Over the past few weeks, fellow GINA GIS analyst Mitch Slife and myself have been busy in the GIS lab cooking up something special. We have been working on creating a new set of shaded color-relief images. Inspired by an old post by Tim Sutton on linfiniti.com, we focused on a fully command line workflow for generating geospatial masterpieces without restrictive obstacles like graphical user interfaces. This fully command line approach will allow us to scale this new hill shading to a variety of other elevation datasets in our archives.
We will be following this post up with links to the new datasets in our Web Mapping Services (WMS) and catalog system so those interested can start using these hill shades in their day-to-day GIS visualization activities.