Did you hear the one about Landsat, Amazon Web Services and Esri?

It could be the start of a very geeky joke, but this is something that i discovered this week and thought i would share with you.

I have long been a fan of Landsat imagery. The data is distributed freely by the USGS and is often your only option for checking out temporal change without having to buy imagery.  Great stuff but i always found it difficult to actually find the right image and download it. The USGS seem to have multiple data stores and i invariably got the wrong one.  Often hunting around for ages to get into the right portal then faffing to select an image before being told i needed to log in. Arrrrrghhh! I can remember my user credentials!

So i was pleasantly surprised to read in a newsletter that Landsat 8 imagery was available in Amazon Web Services (AWS).  I initially thought "Great i can take the feed and pump it into ArcGIS for Desktop or ArcGIS Online" 

However, the AWS is just a catalog of images. Users must use the image filename to select the image they want and this unfortunately means deciphering the file naming convention. So if you have LC80390222013076EDC00 

LXSPPPRRRYYYYDDDGSIVV
L = Landsat
X = Sensor
S = Satellite
PPP = WRS path
RRR = WRS row
YYYY = Year
DDD = Julian day of year
GSI = Ground station identifier
VV = Archive version number

Not so easy. You would need to know which path and row your field site is in, then which day the satellite passed overhead.  

Luckily i discovered, or rather i re-discovered Esri's Unlock Earth's Secrets page which has recently had a refresh.  

Scroll down to find out some of what is possible with Landsats multi-spectral sensor, or click the Try It Live button.  You should now see a Landsat Image and some environmental icons down the left hand side (see pic below)

You can now locate your filed site using the search function and then explore the different bands (different combinations of 3 bands will result in images adapted for detecting various environmental indicators).

But the really useful features in my opinion are:

  1. The Time Function - this allows you to step through the back catalog of images (it shows the most recent by default), to find an suitable image. I live in Scotland and this is really useful as many images are obscured by cloud (there is a cloud filter that helps!).
  2. The Information Function - once i have found a good image i can use the Info button to find out the file name. I can copy this and punch it into the AWS search to download the image

So if you are looking for Landsat images and want a short cut to find ing the best image, you should have a look at the Unlock Earth's Secrets page.  It's really good and the only thing i can think of that would improve it would be a "Get this image" button which linked users directly to the AWS page that serves the downloadable image.

Unlock Earth's Secrets - http://www.esri.com/landing-pages/software/landsat/unlock-earths-secrets