Blaise Mibeck

I ran across some news recently about GPS and realized that I wrote extensivly on GPS during my time as a graduate student in Space Studies at UND. Most of this article is taken from a paper I wrote in 2000.

On May 7, 2009, the United States Government Accountability Office (GAO) reported on the future of Global Positioning System (GPS). The future is not good to say the least. At issue is the real possibility that “in 2010, as old satellites begin to fail, the overall GPS constellation will fall below the number of satellites required to provide the level of GPS service that the U.S. government commits to.”

How did we get to this point? Most users of GPS are aware that many satellites overhead provide the signals they use to pin point their position on a map or track their progress through across town. How many know were GPS came from?

The first GPS was invented in 1610 by Galileo. It involved a telescope and a table of eclipse times for Jupiter's moons. Measuring the altitude of Polaris gave your latitude. By using the eclipsing of Jupiter's moons as “ticks” from a global clock, the time at home base could be determined (using the book of tables). Comparing local time with the time at home base produced longitude, or how far east or west you have gone.

Sure, it seems strange to refer to this as the first Global Positioning System but in principle todays system and that of Galileo are identical. Each has a ground segment, a space segment and a user. Each depend on time for the determination of distance or location. More importantly, the initial application was identical: navigation at sea. Galileo's GPS was submitted to a challenge set by the King of Spain in 1598 for a method of determining longitude. It wasn't until 1761 that John Harrison's marine chronometer became the first practical method for determining longitude.

Even with John Harrison's clock, the problem of position determination persisted. This problem has always been highly important to conducting war. The strategic implication of knowing your position are multifaceted. They affect the principles of warfare that deal with deployment of mass, economy of force, maneuverability, unity of command, surprise and simplicity. More important to land warfare is the challenge of position finding despite Fog of War (FOW). FOW describes the effect of battle field chaos that results in disorganization, loss of central command and casualities due to “friendly fire”. Navel warfare has its own FOW to contend with, but also requires constant attention to one's location due to the featureless nature of the ocean.

Radionavigation, developed in the 1920's, looks similar to today's GPS. Shore-based transmitters and radio direction equipment aboard ships or planes made up this system. Two or more stations were required for the navigator to triangulate his position. This only worked in two dimensions (latitude and longitude) and also encountered problems during bad weather. Regardless, this new technology was being used to tackle this ancient problem.

To understand GPS today – to get the big picture – it is important to realize that the problem it solves is an old problem. By seeing the important role GPS plays in trade and war today's user can better appreciate the the system they take for granted and the politics involved in its use.

The report by the GAO can be found here: http://www.gao.gov/products/GAO-09-670T

I became interested in fish hearing when my 4 year old daughter asked me if fish had ears. I had just told her not to tap the glass on an aquarium because, you will scare the fish!.

It turns out that fish have an organ called the labyrinth balance organ (not related to the labyrinth breathing organ found in bettas and guaramies) and it is very similar to your inner ear. It acts like an accelerometer and it also tells the fish brain which way is up. In fact you could call it a primordial inner ear because it does the same thing the human inner ear does minus the ability to hear distinct frequencies.

So fish have an inner ear, but its purpose is to tell direction. It turns out the momentum in underwater sound waves is high enough that this organ does respond to sound.

The stripe along the sides of most fish is called the lateral line system. It is made up of closely spaced nerve bundles (called neuromasts) in a channel below the skin. These cells are sensitive to low frequency ( below 150Hz) pressure changes that occur close to the fish. The lateral line system is sort of like our ear drum because the mechanism for transduction of the sound is pressure change, but step from pressure change to signal it immediate. Our ear drum relays pressure changes to components in the inner ear that can differentiate between frequencies.

To top it off, the swim bladder in some fish can be sensitive to high frequency sound (above 1500Hz). There are all ready nerves connecting the brain to the swim bladder. The bladder acts as a resonator and this produces signals in the the nerves near by. Fish such as salmon and cod can hear with their swim bladders. Because catfish and carp (including gold fish) have additional structures that connect the swim bladder to the labyrinth balance organ, these fish are most sensitive to high frequency sound.

So fish hearing is composed of three different organs: the labyrinth balance organ, the lateral line system and the swim bladder. They each use a different mechanism to detect sound in different frequency regimes.

This leads to an obvious question: Do fish talk?

Yes the do. I will explain later.

In 2004 a group of Electrical Engineering students announced that they were looking for payloads to fly on an unmanned aerial vehicle (UAV) they were designing. A friend of mine at work and I designed a small particle collector. I will write more about this later.