Re: GPS recommendations?

**stickyjeans69** · 12-17-2007, 07:21 AM

also, the airplane in that video............here's it's engine

http://www.airliners.net/open.file/1265914/L/

every bit of information used in a GPS for an airplane has a time that it's used to keep the people inside who are worth more than any price anybody could ever set safe.

**CingularDuality** · 12-17-2007, 08:31 AM

Originally Posted by sordavie

Triangulation can get you altitude...

Pyramidation?

I remember when I was working on military portable GPS units that if you could hit 12 birds, then the altitude reading would be accurate within 10,000 feet. I just remember thinking that I could probably guess my altitude plus or minus ten thousand feet no matter where I was on earth...

**P8riot** · 12-17-2007, 09:08 AM

Originally Posted by CingularDuality

I just remember thinking that I could probably guess my altitude plus or minus ten thousand feet no matter where I was on earth...

Mine couldn't maintain an accurate altitude to save my life even with every bird in the visible sky locked in. Aviation systems are different and utilize more than just GPS localization for altitude.

I loved my Garmin iQue M5. In addition to things like navigation, you can find most retail establishments, restaurants, gas stations, etc.. with their phone numbers and if it was a restaurant, a description of their menu.

I would frequently use it, even if I'd been to the place before, if I had someone else in the car.. it ended the, Oh - I needed to turn there, syndrome from chatting instead of watching streets and exits.

**mentholated** · 12-17-2007, 09:23 AM

Originally Posted by stickyjeans69

take it you've never looked into some of the things pilots do. the GPS doesnt coordinate with other GPS' it coordinates with a Sattelite like it's supposed too, it also coordinates through a Radio with a control tower that has a Radar and reports positions of nearby aircraft. as far as space travel, no. Aviation navigation is very precise, under Instrument flight Rules. these pilots wouldn't have made it to the runway with out their Navigation equipment.

http://www.flightlevel350.com/Aircra...ideo-2711.html

Pilots control thrust and attitude of an object. And aviation navigation isn't nearly as precise as you'd think it is.

**stickyjeans69** · 12-17-2007, 10:41 AM

heh care to try me on something I don't know in aviation? You're the one saying navigation equipment in airplanes belongs in space ships.

**mentholated** · 12-17-2007, 07:50 PM

Originally Posted by stickyjeans69

heh care to try me on something I don't know in aviation? You're the one saying navigation equipment in airplanes belongs in space ships.

No, I never said I knew more than you about aviation in general. I do know however, that the navigation systems in civilian transportation in general use are not quite as sophisticated as the classified navigation systems in use in craft you wouldn't believe existed even if one were right infront of your eyes, doing 10,000km/h right angle turns.

**CingularDuality** · 12-17-2007, 08:11 PM

Hey, this is my GPS thread. Go start your Area 51 thread in the Sandbox!

**mentholated** · 12-17-2007, 08:32 PM

Originally Posted by CingularDuality

Hey, this is my GPS thread. Go start your Area 51 thread in the Sandbox!

Hey thats a good idea >

. TY.

**sordavie** · 12-17-2007, 09:40 PM

In principle you only need 3 reference points to get altitude. I think any GPS unit with the right software can do it with 4. According to this, http://www.encyclopedia.com/doc/1G1-164222213.html, the accuracy is +-200 ft. Towards the end of the article, the writer writes:

What this means to you as a pilot, is that if you're relying on GPS altitude close to the ground, you probably have a death wish. That tower could be 200 feet taller than you think. Your aircraft could be up to 200 feet closer to the ground than you think.

At higher altitudes, above the terrain, relying on GPS altitude is even more dangerous ... because all the other air traffic is relying on barometric altitude in accordance with FAA and ICAO rules. Even though you might be exactly at your true altitude, the altitude of the other traffic could be several thousand feet off!

(My emphasis added).

Is this what you mean when you say it could be ten thousand feet off? It can be thousands of feet off from barometric altitude readings. But barometric altitude readings don't give your true distance from sea level.

**CingularDuality** · 12-17-2007, 11:41 PM

Originally Posted by sordavie

Is this what you mean when you say it could be ten thousand feet off?

No, I was talking about the tech specs for military GPS units from before civilians were able to purchase them. Specifically Trimble units that I was working on in 1995-1998. They were replaced with COTS gear soon after...

**P8riot** · 12-18-2007, 12:27 AM

Sordavie - You've got the right idea. Nowadays, you can get maybe +/-200 ASL.. but even that alone only allows for 100ft actual error in crossing air traffic lanes.. BTW.. less than 500' is clasified as a near miss an FAA terms and recorded.. That 500' buffer also depends on the class of aircraft being flown.

All flights are managed by ASL + Baro pressure for altitude. GPS alone does not account for pressure - so you get the wide aperature for error without pressure accounting. The factor for ground optimized GPS is processor speed. For ground based GPS, unless your GPS is optimized for altitude instead of location, you GPS treats altitude last, so if it takes .5 seconds for your processor to finally compute altitude.. in .5 seconds.. the satellites are already reporting you several hundred feet off.

Now all that being said. Why do I know this crap? I used to do second seat for Raytheon for 4 years - NOT that I was experienced at flying or anything, but at the time, delivering aircraft to customers only required a pilot and one other person (because experienced co-pilots were in the gulf war at the time), SO.. since Raytheon was a good client of mine I got to fly around.. um.. quite a bit. I've been in three custom Hawker Horizon ER's delivered to Switzerland. ALL had laser altimeters and auto-land features (not FAA approved at the time) that were a real adventure.

So, yeah.. I've played with GPS navigation.. and failures. Yeah, I mentioned the Swiss-trips.. Since this message is so long, I'll continue.

The pilot, also David, was warming some grub for us at 30k in the million dollar 'kitchen' and I was half asleep (monitoring autopilot) headed just over Iceland. SCHREECH SCREECH SCREECH.. MASTER WARN! MASTER WARN MASTER WARN! AP lights shut off, Two of the 11x14 LCD's shut off.. three left, so I know enough to spread out the info across the remaining screens, Oh yeah, did I mention AP shut down? My hands are in suicide grip on the yoke.. keep it steady. POW.. another screen goes down.. only ONE computer left displaying useful digital information (there is still basic traditional instrumentation at the time - FAA required). Dave gets back and lands us in Iceland. Seven Raytheon engineers were there with equipment in 8 hours.. 14 hours later we were on hour way back to S. FL. we were wiped out - other pilots finished the delivery.

Geez, OK, So.. Cing, I prefer Garmin GPS systems. They are easy and complete.. not much more to say..unless you get me started again

**SuperDudeBT** · 12-20-2007, 12:07 AM

I use the HP iPAQ rx5915. It is a full featured windows mobile PDA and a Tom Tom GPS in one. It has 2 GB of internal storage (500 MB is used by maps and programs, leaving you 1.5 GB of space to use). Bluetooth, WiFi, mic, speakers-- pretty much all of the bells and whistles. You can also use the GPS radio with other applications, like Google Earth mobile. I find it cool that I can call people using Skype on it over Wifi.

So, if you need a PDA too, this is a great choice. I honestly rarely use the PDA functionality, but I know that I have it if I need it. However, I NEED and use the GPS all the time. I'm terrible at following driving directions. If I'm going anywhere I'm not familiar, I'm using the GPS. It's thin, too.

It's $400 at amazon.com, that's where I bought it from. It's $500 from HP.

I don't recommend the company "Mio." My dad has one, and the directions are very poor. The interface doesn't seem as easy as my Tom Tom, too.

http://www.shopping.hp.com/product/h...Q3xh!765047840

http://www.amazon.com/rx5915-3-5-Inc...8122901&sr=8-1

**P8riot** · 12-20-2007, 12:29 AM

Thats like the Garmin iQue I had. I loved it because I put all our 2000+ company contacts in it. Frankly.. all the clients and jobsites we have run together. I'd just jump in the car and pull up the contact and hit the 'route to location'. Whether I think I know where I am going or not.

So as long as I specify correctly that I want to go to Riverview High School and not Riverside Middle School.. I don't happily drive myself to Riverside, parking, and looking for a meeting I'm supposed to be at.

Oh.. and it's fun too.. it records information, so it'll show your top speed, etc.. take it on a plane with you. Next time you get pulled over or something, you can show the LEO.. you were actuually doing umm.. uhhh.. OK.. 631 in a 35 zone? If you have a window seat.. or front seat in my case.. you can pick up the at least three satellites to record where ya are.

**marstein** · 12-21-2007, 02:04 AM

I have heard good things about Garmin and Magellan. I have a Tomtom 910 with Linux, 20GB hard disk, bluetooth and voice output. It can also play MP3s, and audio books and show photos. And it is a GPS. I like navigating with the map, but that thing tells you how long you still have to go quite precise and can get you out of unknown cities and finds the closest bar.

The problem is you get dependent on these things. You get used to following the machine. I usually know where I am, but e.g. other members of my household have no clue and if the enter the wrong target coordinates they could end up in the wrong state. I heard about some delivery guys in the UK going 80 miles to the wrong place when their destination was really only a few miles away.

**ScratchMonkey** · 12-23-2007, 03:05 AM

Any good ones built into a watch that'll dump track memory to a PC? (It's ok if the receiver is on the belt and bluetooth's to the watch.)

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