Ship Watching (7 March 25)

A lot of you may not know this blog started as “satblog” about 25 years ago, and was almost entirely devoted to satellite remote sensing. During the invasion of Iraq I monitored the conflict using open source and commercial satellite data, and even broke news from time to time, such as being the first to confirm that Iraq had set the oil fields on fire.

Yesterday I posted on Facebook (to keep the page live) a snapshot of a test image I was working on showing ships parked offshore of Savannah. I was surprised at the likes and shares, so here is a bit more on this type of image and how it is used. First, here is a “big picture” view from the NOAA21/JPSS-2 Satellite taken at 1:36am this morning. This is a special sensor that was originally flown on the Defense Meteorological Satellite Program, and lets us see night time lights – something very useful for a variety of things not related to meteorology …

Zooming in on coastal GA/SC, you can see where the cities and towns are, as well as clusters of lights offshore. Most of these are ships …

I’m sure some readers who are in the shipping business can pontificate at length on why these vessels are parked out there – as I understand it they are waiting for tides, harbor pilots (link to Savannah Harbor Pilots Association), or and/or their assigned parking time. A reader highlighted the Georgia Ports Authority’s web page and list of ships with lots of data like arrival times, etc.

The logistics involved in global shipping is complex – from making sure berths are open at the right time, enough containers are available in the right places at the right time, and so forth. It’s a hidden aspect of our complex global economy – and one that is very delicate and vulnerable to disruption, and takes a lot of smart people to make it work. Worth considering.

I have a couple of targets labeled as moving. How do I know this? As you might suspect, from comparing images taken some time apart … here’s the neat slidee thingee to let you compare images taken from NOAA 20 and NOAA 21 about an hour apart:

So by georeferencing these images and measuring the distance it has traveled, we get the course and speed …

Now, that’s not as simple as it might sound, since these satellites are moving, the orbits are different, and so forth. There are clouds and the atmosphere can distort things. But that’s the basic approach.

So, why not just go online and look at ship tracking data like this, from vesselfinder.com or a commercial source?

That’s another piece of the puzzle for some of my work. Ships have transponders, which is where that data comes from. But not every ship runs with their transponder on all of the time for various reasons, such as military, or the various “shadow fleets” running weapons, oil from sanctioned countries, and so forth. So using satellite data is a way to independently track this activity.

I use data from these satellites for a variety of purposes not related to meteorology or shipping. By monitoring night-time lighting and land cover changes, I can keep infrastructure data sets updated and estimate things like how much of a countries GDP is going into that sort of thing. By monitoring temperatures and aerosols I can tell if factories are running full time – or if they have scaled back, indicating a slowing economy, supply disruptions, or labor problems. The same applies to conflict zones – war is hard on both people and the earth, and these impacts can be seen from space.

There is higher resolution imagery available (these satellites operate at a resolution of 375 meters), but most of that is commercial and/or classified. I continue to use public/open source tools as a cross check, and to see what can be learned by anyone with the right tools, and as a constraint on what higher resolution data is needed.

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