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.
By experimenting with the photovoltaic reaction in solar cells, researchers at MIT have made a breakthrough in energy efficiency that significantly pushes the boundaries of current commercial cells on the market.
We looked at a number of sources to determine this year's greenest cars, from KBB to automotive trade magazines to environmental organizations. These 14 cars emerged as being great at either stretching fuel or reducing carbon footprint.
From Dell / Intel® New Paradigms in Design Work Scott Hamilton, vertical market strategist for Dell Precision workstations, 5/2/2013 3
Early in my career, I worked as a draftsman and remember the days of drawing on vellum with numbered pencils and Mylar with plastic lead. This was a fun experience in the sense that I ...
I've been using workstations for more than 10 years and love finding ways to get more performance from my system. With demanding professional applications that require more power each ...
A lasting memory from my first job as an engineer in an auto assembly plant is standing on hard concrete at six in the morning, vending-machine coffee clutched in hand, listening to ...
A quick look into the merger of two powerhouse 3D printing OEMs and the new leader in rapid prototyping solutions, Stratasys. The industrial revolution is now led by 3D printing and engineers are given the opportunity to fully maximize their design capabilities, reduce their time-to-market and functionally test prototypes cheaper, faster and easier. Bruce Bradshaw, Director of Marketing in North America, will explore the large product offering and variety of materials that will help CAD designers articulate their product design with actual, physical prototypes. This broadcast will dive deep into technical information including application specific stories from real world customers and their experiences with 3D printing. 3D Printing is
To save this item to your list of favorite Design News content so you can find it later in your Profile page, click the "Save It" button next to the item.
If you found this interesting or useful, please use the links to the services below to share it with other readers. You will need a free account with each service to share an item via that service.
Tweet This
3 
