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Global Positioning System

 

 

GPS - What is it?

Imagine being able to pinpoint your position anywhere on the face of the earth 24 hours a day - down to an accuracy of 100 feet (30 meters) or even less. And in any kind of weather, blinding rain or driving snow white-out. And on any surface - land, sea or air.

The Global Positioning System utilizes the $13 billion system of satellites in sun-synchronous orbit above the earth, developed by the US department of defense. Access is free to all users and provides accurate location and timing information. GPS is literally revolutionizing a host of activities including air, land and sea navigation, vehicle and vessel tracking, surveying and mapping, asset and natural resource management, and network synchronization.  An example of GPS being used in the 21st century is in the iphone from o2. They have managed to use a mix of GPS and cell tower triangulation in their latest mobile phone to allow mapping through custom apps and of course the well known Google maps application.

Imagine you are Robin Hood and you are leading your merry men from one point to another. Using hand-held GPS you record your location at the point of starting (Sherwood Forest). Along the way you store your position at regular intervals. Lost your camp in Sherwood Forest? You just backtrack using the GPS and it will guide you to each of the stored locations.

Ok, now you are Goldilocks, intent on finding the house of the Three Bears. You know the general location so you do a structured search in the woods. Record your start location and start searching. When you find the house - record the location - and any time you feel like a bowl of porridge the data in your GPS will guide you right back to the spot. Alternatively use the start location and direction finding facilities of your GPS to find your way home. Very useful for those occasions when you need to get out of a tight spot fast.

 

Garmin GPS II Plus Receiver

I bought (and later traded away) the Garmin GPS II Plus handheld receiver.  It replaced my older Garmin 40, which I had been using for a number of years.  How do I like it?   IT IS GREAT!  I was not aware of just how much progress had been made by the folks at Garmin.  The GPS II Plus provides maidenhead grids, which is used in many of the ham radio contests.  Being able to quickly determine your grid square is a nice plus during contest rover operation.

My GPS 40 did not do very well when walking through a forest, or when the horizon was partially blocked such as is often the case when driving in the mountains in Arizona.   The GPS II Plus has much better sensitivity (or the external antenna is much better than the internal patch antenna).  I used to get the good old "Poor satellite coverage" message on my GPS 40 quite often.  I have yet to get that on GPS II Plus.  In fact, I tried it while sitting in my living room, which is pretty much centered in my house.  It showed good receive strength on 3 birds and adequate on another one.  Not bad for being inside a wooden building. 

One of the main reasons I selected the GPS II Plus was for the external BNC antenna connector.  Having had less than desirable experiences with the GPS 40, I wanted to be able to use an external amplified antenna.  I did a lot of web searching, and spoke with a local friend to get some more information. 

During a recent business trip to Pennsylvania, I took the GPS II+ along.  After plugging the power cord into the rental car's cigarette lighter socket, I was surprised (not to mentioned impressed) to see it acquire 6 sats and locked on to them in less than 30 seconds.  I checked the distance back to my home in Arizona and found it to be almost 2100 miles.  I was expecting the receiver to take a minute or two to figure out where it was, since the last time it had a good fix was back in Arizona.  I would give it a grade of A+ in the warm start category based on this performance.

It would seem that one of the best after-market antennas come from Lowe Electronics, in the UK.  I could not find a single bad comment about this antenna.  It is very small, magnet-mount 26dB amplified antenna.  I found a very friendly US dealer (so you don't have to order it to from from England).  The name of the dealer is Les Sullins, at D & L Antenna Supply.   D & L can be reached at either  3410 Gibbs Road, Kansas City, KS 66106-3308, or via e-mail at Info@wavehunter.com.   You can call them at 913-677-8674, or use the toll free fax order line 1-800-912-9293.  By all means, check out their web site at www.wavehunter.com.

 

Garmin GPS III+ Receiver  

I traded off an old 486 notebook PC and my II+ receiver for an almost new III+ receiver.  I had pushed the limits of my II+ and was looking for several features that the II+ could not offer; more track log points and the map uploads from the Garmin MapSource software to name a few.  The 1900 track points, when running at 30 second intervals, works very well.  I get tracks that are accurate enough to easily repeat, and I can run all day without filling up the memory.  I use the MapSource Roads & Rec CD and have found it to be a great addition to my off-road travels.  I was surprised to find that many Jeep trails are on it.  And even if they are not, there is  plenty of other information that helps one determine where you are.  I still (and always will) rely heavily on OziExplorer and my collection of 7.5' USGS topo CDs, as well as the  maps I can print from Ozi.  All together, it makes for a great navigational aid.

The III+ has better pixel resolution.  It took me a while to get use to it, since the lettering was a bit "thinner" and I was use to the big fat characters from the II+.  The III+ also has excellent receiver characteristics and I have no trouble tracking the sats from within my Jeep while using the stock antenna.  The more I use it, the more comfortable I get with it.  I wish Garmin had made the option to turn the track log on and off a bit easier to access.  It is buried down about 3 or 4 menu levels.  I find myself digging for it time and time again.  Oh well, maybe the next generation of firmware will allow you to have a user defined interface (although you can change many of the display fields on several of the III+ viewing screens now).

I highly recommend this GPS receiver for anyone that is serious about off-roading.  Combined with good mapping software (aka., OziExplorer and DRG topos), it makes it really easy to enjoy the scenery and not worry so much about taking the wrong turn!

 

Garmin StreetPilot III Receiver  

No, I didn't buy this pricey little GPS receiver.  However, a good friend of mine recently purchased one and was kind enough to let me try it out for a few days.  I was at his house when he offered to let me try it.  Upon leaving his place, I plugged in the 12V power cord and fired up the GPS.  Having owned had 3 Garmin GPS receivers before trying this one, I decided to see how easily the StreetPilot III "drove" without looking first at the owners manual.  I quickly determined how to enter my street address, along with my city and state, and told it to calculate a route to my home.  I was about 3 miiles and 3 turns away from the house when I did this....a simple enough test. The Garmin MapSource North American City Navigator CD that came with the unit had been uploaded into it so I was all set to go.

Sure enough, it told me I was about 1.2 miles away from making my first turn.  After the turn, it again announced how far I had to go on Camelback before turning left on to the side street that would then have me about 3 blocks from my house.  At that point, I became very disappointed with the route directions.  I am not quite sure where it thought my house was located, but let me tell you that had I followed the directions, I would not be sitting here in front of my PC typing this review.  Even when I pulled into my driveway, it kept telling me I needed to turn north and drive someplace....beats the heck out of me.  Did it get me close?  I guess so....but for this much money, I would have thought it would have at least gotten me onto the correct street.

As for the receiver, I am NOT impressed.  I sat the new StreetPilot III on my desk and pulled out my trusty old III+ so I could do a side by side comparison.  Both are using the little Garmin stick antennas that attach to the back of the unit.  It took the StreetPilot III almost 5 minutes to announce that the satellite coverage was poor.  I checked the satellite page to find that it had a 2D lock on just 3 sats.  In contrast to this, my III+ had a 3D lock on 7 sats in just 15 seconds.  Oh yeah....did I mention they were sitting side by side on my desk?  Even after letting it run for a longer period of time, it never made it to more than 4 sats....and the signal strength of those were showing to be half of what my III+ was pulling in.  Several minutes later, my III+ was showing only 5 strong sats when the StreetPilot announced that it had lost contact with the sats (I checked the status screen and it was showing 2 weak sats).  Later on, it started track 5 or 6 sats with 3 or 4 of them showing good strength....I still don't quite understand why the brand new StreetPilot III is show sub-standard performance compared to my several year old III+.  Oh...in case someone was wondering, they were both connected to a 12V power source so it was not a case of having weak batteries.

I was poking around in the menu screen and found the track log function.  It was on (so I turned it off) which meant that it had recorded my route coming home. Now it is possible that the feds have enabled the selective availability on the GPS sats since we went to level orange the other day for the Homeland Security status.  If selective availability had been turned on, this would certainly explain why the directions I was getting were off somewhat.  I started OziExplorer and downloaded the track log into it.  I brought up the appropriate USGS topo map and checked to see if my house was at the end of the track.  Sure enough, it was....the track came right down the street in front of my house, yet, according to the route screen, I was more than 100 yards south of my house.  So....according to my mapping software, the GPS has me sitting right where I should be....but the automatic route program in the StreetPilot III says I need to be another street over.  Now you tell me, what the heck good is a "StreetPilot" going to do me when IT can't figure out where IT is?

OK....maybe this wasn't much of a scientific review, but all in all, the only thing I find impressive is the color display.  After that, I'll take my old III+ since the receiver seems to do better and it won't eat a half dozen batteries in as little as 2 hours (2 to 20 hrs is what the StreetPilot III book says). 

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