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ECE
6390 Radiolocation Scavenger Hunt 3
Late for Dinner Team Perihelion |
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Our
Task
Your are running late for your anniversary dinner. Your significant other has called you from outside the fine restaurant where you are supposed to meet for a romantic outing. Unfortunately, your spouse's cell phone call is cut-off before you can catch the name of the restaurant. Your return calls keep dumping to voice mail. If you miss this dinner, it will be a very dangerous situation indeed. You have one thing going for you. Your spouse's cellular phone has a trial GPS chip inside that records pseudoranges calculated from 3 received GPS signals and then calculates user position. Unfortunately, the phone must have been operating in a partially occluded location since the full 4+ pseudoranges required for 3D GPS location are not available. Since you are an electrical engineer, of course you can hack a digital cell-phone in seconds. You discover that, through some quirk of Springularizon's protocol, your handset somehow has your spouse's pseudoranges recorded in memory. You must use these pseudoranges to find the location of the restaurant.
Information Given
speed of light (c)=299860.00 km/s earth radius=6380.00 km satellite altitude=20,200.00 km
Questions How did you solve the range equations? Because we knew the area of interest was in Georgia, we partitioned this area then solved iteratively using Matlab. The code may be viewed on the solutions page. Are there any ambiguities in your technique? How did you address them? There are no ambiguities in this technique because the user is allowed to specify a relatively small area to 'search' for the area of interest. Can you place a confidence interval on your position estimate? From our calculations, we conclude that the the ranging error to is about 33 meters. What factors that we did not consider might affect a realistic GPS ranging estimate? Additional losses such as ionospheric and tropospheric delay, ephemeris errors, satellite clock errors, and multipath errors are not accounted for.
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