When I was a freshman engineering student at the University of Southern California in 1982, I got to go on a tour of TRW’s Space Division where I saw one of the first GPS satellites being assembled. We were told that this technology was going to revolutionize navigation. Yet I couldn’t help but wonder how the satellites would know where I was. Today that thought reminds me of a trip to the mall when my children were very young. We looked at the mall map and found the label saying, “You are here” and my son asked me how the mall people knew where we were.
So goes the world of GPS. GPS technology has evolved over the past 27 years and become much more accurate. Nonetheless, the basic principle remains the same and you don’t have to be an RF expert or a math wizard to understand it. With GPS, most of the satellites know very little except the exact time. The GPS unit you hold in your hand or in your car has all the smarts. The simple version of GPS, without any of the fancy corrections follows basic geometry.
It goes like this. Say you know that you are a distance of 100 miles from a point of known location, even if you know nothing about direction, then you know you are someplace on a sphere with a radius of 100 miles from that point. Now, let’s say you know that you are 100 miles from one point and 50 miles from a different known point. In this case your location is a point which is common among two spheres of radios 100 miles and 50 miles respectively. Since the intersection of two spheres is a circle, you know you are some place on that circle. Finally, let’s add a third point. Using the same logic you know your location is the intersection of three spheres. Geometrically speaking, the intersection of three spheres is exactly one point. So all your GPS receiver does is calculate the distance from satellites of known location by measuring the delay in the time-stamped signals from the satellites, then calculating your point location by intersecting spheres. Now because this measurement is not perfect, we add extra satellites to reduce the error and provide a time reference. All you really need to know is basic geometry.
In this new Design News feature, "How it Works," we’re starting off by examining the inner workings of the electronic cigarette. While e-cigarettes seemed like a gimmick just two or three years ago, they’re catching fire -- so to speak. Sales topped $1 billion last year and are set to hit $10 billion by 2017. Cigarette companies are fighting back by buying up e-cigarette manufacturers.
Advertised as the "Most Powerful Tablet Under $100," the Kindle Fire HD 6 was too tempting for the team at iFixit to pass up. Join us to find out if inexpensive means cheap, irreparable, or just down right economical. It's teardown time!
The increased adoption of wireless technology for mission-critical applications has revved up the global market for dynamic electronic general purpose (GP) test equipment. As the link between cloud networks and devices -- smartphones, tablets, and notebooks -- results in more complex devices under test, the demand for radio frequency test equipment is starting to intensify.
Much of the research on lithium-ion batteries is focused on how to make the batteries charge more quickly and last longer than they currently do, work that would significantly improve the experience of mobile device users, as well EV and hybrid car drivers. Researchers in Singapore have come up with what seems like the best solution so far -- a battery that can recharge itself in mere minutes and has a potential lifespan of 20 years.
Some humanoid walking robots are also good at running, balancing, and coordinated movements in group settings. Several of our sports robots have won regional or worldwide acclaim in the RoboCup soccer World Cup, or FIRST Robotics competitions. Others include the world's first hockey-playing robot and a trash-talking Scrabble player.
Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.