Brain Log - Think it out. Write it down.

Although there are windows binaries available and an msi installer for elog to have automatic thumbnail generation of images you have to install Imagemagik and Ghostscript. Rather than install these into a normal windows environment (when would I run them form a c-prompt???) I decided I'd rather do it under cygwin. So I installed elog on windows using this recipe:

• In cygwin install openssl-dev, init scripts, chkconfig, imagemagik and ghostscript.
• Download the latest elog tarball.
• Untar it, cd inside, and execute ‘make’ followed by ‘make install’
• Then start it up with /etc/rc.d/init.d/elogd start
• Point a browser to http://localhost:8080

Slashdot recently reported that the National Snow and Ice Center has just issued a statement that their measurements of ice coverage for the past month have been grossly under estimated. There is a lengthly discussion about it here where they describe the problem as “sensor drift”. Nothing scandalous here, they're being completely forthright. But I must admit I do not understand this statement (from the page above)

Some people might ask why we don't simply switch to the EOS AMSR-E sensor. AMSR-E is a newer and more accurate passive microwave sensor. However, we do not use AMSR-E data in our analysis because it is not consistent with our historical data. Thus, while AMSR-E gives us greater accuracy and more confidence on current sea ice conditions, it actually provides less accuracy on the long-term changes over the past thirty years. There is a balance between being as accurate as possible at any given moment and being as consistent as possible through long time periods.

It seems to me they're saying, “Well we've thought the earth was flat for centuries. But this new instrument says it is really a sphere. But that doesn’t give us a consistent historical record so we're going to continue to consider it flat.”

Maybe someone else can explain it to me – over a beer.

We recently did some testing to see how the 1-Pulse Per Second signal drifts when a GPS unit no longer has a fix. We tested a SiRF III ET-332 GPS engine and a Garmin 17N. The details of our tests and results are here..

In our test, the SiRF unit drifts only 140 microseconds in 2 hours. These results will be temperature dependent, of course, and so your mileage may vary.

This is the coolest thing ever. Wolfram – the makers of Mathematica have an online intergrator in which you can enter your equation, click a button and it spits out an indefinite integral. I would have KILLED for this while I was in school!!!

An online version of this classic text can be found here.

The American Practical Navigator

Today I googled a new acquaintance to look up his address and look what Google gave me:

I don’t know what kind of searches warrant a timeline, clearly not all, but I think it is a very cool option for presenting information.

As many have pointed out Google Earth 5.0 now includes ocean bathymetry!

While this is very cool on a whole host of fronts, their rendering of the data shows how difficult it is to conduct a high-quality bathymetric survey and blend it with other data to create a map that makes sense. They may have started with poor data, but their handling of it is abysmal. Here’s what I mean.

This is the continental shelf just off Virginia Beach. It’s hard to tell if these blips in the bathymetry are a gridding artifacts, a registration artifact with one of the data sets or maybe even a data set with a problematic vertical reference.

Here’s another:

This one is near Cape Hatteras.

Today we got to see the basic operation of a new (to us) Gavia AUV which the Center for Coastal and Ocean Mapping at the UNH shares with the University of Delaware.

Art Trembanis came to show us its bells and whistles. It has quite a few. Several things right out of the box impressed me.

• It runs Linux (RH9 I think).
• It has an ethernet backplane and each module has it’s own IP address.
• It has an SDK that will allow us access to the navigation state variables and, presumably the ability to enhance its smarts.
• It has an 802.11a(b?/g?) AP in a short sail on top so you can connect to it via WiFi.
• It can fall-back to Iridium when the WiFi doesn’t work, or even to a WHOI acoustic modem (I think our’s is the first to have a whoi modem.)

I admit I'm not an excel fan, but this is very handy:

To insert current date, press CTRL-; in the chosen cell. 

To insert current time, press CTRL-SHIFT-;. 

To insert current date and time together, press CTRL-;-SPACEBAR CTRL-SHIFT-;