Occasionally one comes across a particularly handy site. Taking Derivatives is just that – for checking your work of course.
I'm at the AGU Ocean Sciences meeting in Portland, OR this week. There have been many fascinating talks. One that particularly caught my eye was by Jerry Smith (Scripps), which compared theory with results from a newly developed “phased array doppler sonar”.
Heres an animation of some results from Dr. Smith’s web site.:
After my upgrade to Snow Leopard I was having trouble getting Fink Commander working right. The app would load but not display anything in the table. After some searching I found this link which suggests that I follow the directions, install perl588, and set the path to perl in the Fink Commander preferences to the new version. It works!!!
I just stumbled across a fascinating and exiting looking image editing site Aviary (that’s browser based and fee!). Check it out!
I just got back from New Zealand where we ran our Gavia AUV in several lakes and Tasman Bay. Most of our work was related to water chemistry rather than seafloor mapping but it was super fun and very interesting. On one of our adventures in Tasman Bay we drifted over Gavia’s path and caught a glimpse of here on the boat’s echo-sounder. I took a snapshot. Its the blob about 19.5 m down under the cross-hairs.:
I was recently sent a link about the new Parrot AR.Drone remote control quad-rotor helicopter. It is navigated using the tilt sensors of the iphone which is cool in itself. But it also has a live video feed from one of two cameras back to the iphone so you can see its poing of view. It comes with an optional shroud for the rotors so you can bump into things if your flying in tight spaces. Check out their video:
As if all this isn’t enough, the very best thing about it is that they are planning to release a software developer’s kit for it! Oh the science we could do. Now I wonder what payload it might be able to carry.
We'd need a small onboard auxiliary power supply, data logger, a GPS, and maybe a tilt sensor. Ocean Server has a small enough attitude sensor with onboard magnetic compass. Yes, there’s lots of cool stuff we could do with one of these.
Neato Robotics has just released a competitor to the Roomba (iRobot’s vaccuum cleaner). This is the first commercial consumer robot I know of tha uses SLAM – (Simultaneous Localization and Mapping) in which a vehicle maps its environment as it navigates through it allowing it to keep track of where it has been and where it is going.Their robot does its mapping with a laser scanner. Very cool.
Today I figured out a way to execute python code from within MATLAB. This wil work on OS-X and Linux and a variant should work under Windows – depending no your python installation. Here’s how it works.
First create the following bash script:
#!/bin/bash
#
# Val Schmidt
# CCOM/JHC
# Jan 2010
#
# A script to provide a wrapper for execution of python from MATLAB.
PYTHONCODE=/Users/vschmidt/svnsandbox/Gavia/python
/usr/bin/env python $PYTHONCODE/$@
Be sure to modify the PYTHONCODE variable to point to the directory of python scripts you want to execute. Make the script executable (chmod +x executepy.sh) and put it in your path somewhere.
From within MATLAB you can execute your script like this:
unix('source ~/.bash_profile; executepy.sh pythonscript args')
Where pythonscript is the python script you want to execute and args are it’s arguments. It is assumed here that.bash_profile contains your PATH definition (or redefinition). You may have to modify that. You could also modify your PATH on the fly rather than the source statement above if there are things in .bash_profile you don’t want MATLAB’s shell to execute.
This method doesn’t return anything to MATLAB directly. I'm not aware of a way to do that, other than saving the results of your python script to a file that MATLAB can natively read in a subsequent command. (See scipy.io.savemat.)
Today for a project I'm helping with in ocean acoustics I made a nomograph of the differenced in receive time of a transient signal that follows both a direct path and a bottom bounce trajectory, as a function of range.
As a submariner in the Navy We did this kind of ranging all the time, but I've never properly done the calculations complete with ray-trace model. You can see some wiggle in the curve at the most distant ranges where my algorithm for detecting where the two ranges intersect gets a little wonky.
I just ran across this site which shows a 10 minute delayed feed of Airport traffic into and out of Logon International Airport. Check it out!
This is really cool, but isn’t this a security threat? I wonder who uses this. It won’t load on my iphone so it is not likely something you could scan before coming to pick someone up. You certainly get a feel for what it must be like to be an air traffic controller – Shew! Fun to watch.
I wonder if the Coast Guard would ever do this for shipping via AIS. (“No” is probably the answer to that question.)