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Which GPS is the most accurate?

Question:
Hi,

I'm interested in buying a handheld GPS mainly for biology survey (I am a biology student). I am interested in a price range of $150-$200. The most important thing for me in the GPS is its accuracy. I have read on the net that the Garmin 12xl is one of the most accurate GPS. They didn't say any thing about the Magellan one.

I am thinking of buying the Garmin 12 or the Magellan 315. What do you recommend? Which one is more accurate? Are there any better ones in that price range?

Thank you for your help

Asaf

Answer:
Asaf,

The accuracy of GPS receivers are all affected by the Selective Availability that the government has placed in the GPS signal sent from the satellites. Selective Availability sends an erroneous location to the receiver randomly so the accuracy can be affected. The accuracy can be off as far as 100 meters. For outdoor applications this is not a large problem. To combat the selective availability the receiver companies have put in averaging so that the receiver will try to average out the location.

Now other things can affect the accuracy such as the satellite geometry. Satellite geometry is where the satellites are located in the sky. The farther apart from each other the more accurate the position. The satellites work very similar to triangulation. The area that all of the satellites intersect is the receivers location. If you have two satellites that are in the same area in the sky then the area of intersection is greater and the actual position is less accurate.

With all of this said no receiver manufacturer will claim more than 100 meters accuracy with Selective Availability activated. In all of our testing we have found that we are usually within 30 meters of the actual location. So the things that you want to get out of a receiver is ease of use, 12 parallel channels, battery life, and durability.

I have not had the occasion of using the GPS 12 from Garmin yet but I have used the GPS 315 from Magellan and I would recommend it. The accuracy will be the same for either unit and they both use averaging to help diminish the effect of Selective Availability.

Both of these units have roughly the same features, battery life and capabilities. The difference is the Magellan uses only 2 AA batteries instead of the 4 that the Garmin uses.

I am sorry that I couldn't give you the single answer you need but you have narrowed it down to two good receivers.

Jeff Porcaro
Contributing Editor
GearReview.com



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