Spot the difference

I have been working for absolutely AGES to do something that on the surface of it seems really easy (and perhaps a little pointless). Look closely at the following two images:

This is an AVHRR image (thermal/infrared) from 1999 (my test year...which just means it is the data i processed first!) The red line is the coastline (land at north). This is the Mertz polynya area (the same area as the false colour SAR/AVHRR shown previously.

Have you spotted the difference yet? I will give you a clue. It is the cloud. OK to be more precise it is the removal from the image of a particular type of cloud - a little bit of cloud over an open water area.

It is important because this little bit of cloud is over a polynya. It was incredibly complicated to remove it. First i had to identify the cloud and then decide if it was cloud over open water (and thin ice) and also if it was a designated polynya area. I am not absolutely sure yet whether it will pay off in the long run to have spent so much time doing it. What it does mean is that for a little extra processing time i can get a cloud mask with the added advantage of a more precise open water definition. Automatically. When you have thousands and thousands of images automatically (and accurately of course) is how you want things to go down.

I have sent a lot of time testing and refining (currently) 18 cloud identification algorithms BEFORE deciding that i didn’t really care that much! I was actually only interested in the open water areas and identifying any cloud over that open water. Took a lot of effort to find out what i didn’t need to know.


Who knew?

Well me. Now.

I learnt so much especially about things i didn’t know i needed to know about. Often people doing research forget that the failures (or seemingly lost research threads) can teach you a lot and be vitally important in order to come close to finding out “truth” or “an understanding”. I learnt a lot about the AVHRR instrument, what it records/measures and about clouds and cloud behaviour in Polar Regions.

if your very lucky next blog may introduce the joys of noise.