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Posted: Sun Sep 24, 2006 4:29 pm Post subject: Bluetooth GPS receiver- big range of speeds
I have a Dell Axim X51, looking to pair it with a BT GPS receiver.
The thing is, I need the receiver to be able to cope with speeds from walking (for when I'm traipsing up and down mountains) to flying a KingAir at 250-300mph. For both of these applications I will be using Memory Map.
In between, I intend to pair it with Destinator 6 (or other) to warn me about "Safety" Cameras.
I've been looking at Daisy Technology's (http://www.gpssolutions.biz/?navigate=bluetooth) BT GPS receiver and it seems, practically, to be the way to go.
Two questions then:
1. should the choice of GPS receiver be affected by the large range in speeds?
2. to what extent does the chipset and the protocol determine how suitable the GPS receiver is for low and high speed applications?
Many thanks in advance. I use GPS all the time in my work (aerial surveying) but this, quite literally, is rocket science to me!!!
Joined: 24/06/2003 00:22:12 Posts: 2946 Location: Escaped to the Antipodies! 36.83°S 174.75°E
Posted: Sun Sep 24, 2006 4:54 pm Post subject: Re: Bluetooth GPS receiver- big range of speeds
Tinpusher wrote:
1. should the choice of GPS receiver be affected by the large range in speeds?
2. to what extent does the chipset and the protocol determine how suitable the GPS receiver is for low and high speed applications?
The receivers will all work fine at a large range of speeds. I've used my Garmin GPS at speeds of up to 686 MPH with no problems! They do have a max speed but I think it is well past supersonic so you should be OK in the KingAir. ;) When flying, the GPS shows your actual "Speed Over Ground", but I'm pretty sure you will be well aware of that.
As for slow speeds (ie walking) watch out for the "Static Navigation" feature on Sirf III GPS units - you want to switch SN off if you are walking or it will only update your position every 50 meters or so. :x I'm pretty sure memory map is aware of this and they have a tool to do it for you. _________________ Gone fishing!
Thanks also for that information. I'm aware of the SiRF III Static Nav issue. Kind of put me off getting something with the SiRF chipset. I was hoping to get something whose output is NMEA 0183. Does this provide a solution to the Static Nav issue (without the faff of turning SN on/off manually)?
Joined: Jan 14, 2005 Posts: 19638 Location: Blackpool , Lancs
Posted: Sun Sep 24, 2006 5:18 pm Post subject:
The NMEA protocol that most GPS devices use for communication outputs speed in knotts, the software on the PDA or PC converts this to MPH or KPH. There is an upper limmit from memory it is in the order of 1800 knotts (not many aircraft currently flying can get any where near that! )
Beware of using the Memory Map application to switch the SN on and Off. I have found it works fine on WM2003SE devices, but with WM2005 it leaves the reciever in SiRF mode, so I also use the early TomTom GPS driver (vs 2.06) to switch it back to NMEA mode once the SN mode has toggled to what I need.
Go for a decent SiRF-III equipped GPS device, they are better in terms of sensitivity, I would also check that the operation of Bluetooth doesn't cause any malfunction to the aircraft coms, AP, ILS etc if in doubt go for a cabled reciever instead - Mike
Joined: 24/06/2003 00:22:12 Posts: 2946 Location: Escaped to the Antipodies! 36.83°S 174.75°E
Posted: Sun Sep 24, 2006 5:41 pm Post subject:
Tinpusher wrote:
damn, that's some flight I'd like to do. 686mph at 28ft!
No, it was more like 37,000 ft but that screen shot was taken after the flight when I was back on terra firma and shows the maximum recorded speed.
Tinpusher wrote:
I'm aware of the SiRF III Static Nav issue. Kind of put me off getting something with the SiRF chipset. I was hoping to get something whose output is NMEA 0183. Does this provide a solution to the Static Nav issue (without the faff of turning SN on/off manually)?
Pretty much all GPS units will output NMEA format, they can also do Sirf mode but not many applications use it. Many of the GPS units available today use the Sirf chipset so they will all need the static nav switching off.
In theory, once you have switched static navigation off, it should stay off so it shouldn't be a problem. But if you run the battery dead then the reciever can lose it's settings and you have to switch it off again. It really shouldn't be such a problem unless you run the battery dead.
Joined: Feb 23, 2005 Posts: 376 Location: Catford, London, UK
Posted: Thu Sep 28, 2006 4:03 am Post subject:
Skippy wrote:
Many of the GPS units available today use the Sirf chipset so they will all need the static nav switching off. 8O
Hi,
I think most of the SiRF GPSs now available have SN switched OFF by default (because of the slow speed limitations). But some car navigation software may turn it ON, although SN was more applicable to SiRF2. So, Tinpusher, don't be put off getting a SiRF3 receiver (but heed the warnings from Mike and others).
However, if you don't want a SiRF receiver, some people are now favouring Nemerix or MTK chipset devices, which may not have the sensitivity of SiRF, but might give more stable location data or longer running times, etc.. We're eagerly waiting for a detailed comparison here.
I am more amenable now to getting a SiRF chipset GPS.
Quote:
Pretty much all GPS units will output NMEA format, they can also do Sirf mode but not many applications use it.
This is interesting to me, because I have a couple of applications that use the NMEA input (e.g. Garmin's Flightbook application). Can you expand on this? _________________ Home - Dell Axim X51 + BT359 + D6 & MM
Work - IGI CCNS4, Vexcel Ultracam D & Somag GSM3000, X-Treme L1/L2 GPS receiver all shoved into a Piper Chieftain, registration G-OSGB. See the results on http://local.live.com/
Joined: 24/06/2003 00:22:12 Posts: 2946 Location: Escaped to the Antipodies! 36.83°S 174.75°E
Posted: Thu Sep 28, 2006 3:26 pm Post subject:
Tinpusher wrote:
This is interesting to me, because I have a couple of applications that use the NMEA input (e.g. Garmin's Flightbook application). Can you expand on this?
Sure.
NMEA has become the de-facto standard for GPS use.
In practice, virtually every GPS receiver outputs (or has the option to output) NMEA and virtually every Sat Nav system or "GPS Aware" program accepts (or has the option to accept) NMEA input.
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No, it was more like 37,000 ft but that screen shot was taken after the flight when I was back on terra firma and shows the maximum recorded speed.
