Author Topic: Handheld satnavs and GNSS  (Read 3049 times)

Hugh Westacott

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Handheld satnavs and GNSS
« on: August 22, 2015, 05:52:45 AM »
The first printing of my book The Walker's Handbook; Everything you Need to Know about Walking in the British Isles has almost sold out. for the 2nd impression, I'm taking the opportunity to correct one major factual and elementary error, and a couple of typos.

In his helpful and perceptive review on this forum, Ianj37 queried whether it was possible for handheld satnavs to receive signals from GLONASS. Here is the relevant passage which I should be most grateful if some of the experts on this forum would comment and correct (some of the formatting has been lost in cutting and pasting). I've highlighted in red what I believe may be incorrect but I'd welcome additional corrections.

Definition of terms
2 The terms used in connection with satellite navigation systems have not yet been standardized and are sometimes confusing and self-contradictory. Those used in this book are defined here:
   .   a)  The Global Navigation Satellite System (GNSS) refers to the system of circulating satellites and the signals that they transmit. They are transmitted from the satellites of

• the Global Positioning System (GPS) operated by the United States
• GALILEO operated by the European Space Agency

• the Global Navigation System (GLONASS) operated by the Russian 
authorities

• BDS (formerly known as Compass and Beidou-2) operated by the 
Chinese authorities
Note that signals from all four systems are compatible and can be received by most satnavs, smartphones etc. Other countries are also developing navi- gation satellite systems.
   .   
Description of the Global Navigation Satellite System
3 The satellites of the four organizations, the Global Positioning System (GPS), GALILEO, GLONASS and BDS that make up the Global Navigation Satellite System transmit signals that can be picked up by a handheld satnav that converts the information into geographical coordinates. These will, depending on the sophistication of your handheld satnav, enable you to:
   .   a)  Establish your position anywhere on the earth’s surface to within 5 metres.
   .   b)  Establish a series of coordinates from a map,and in put them into a hand- held satnav and then navigate to each one in turn.
   .   c)  Record a route you are walking, and then to save it and use it again later.
   .   d)  Plot the route on a computer mapping system to see where you have been.
   .   e)  Share routes with others via computers.
   .   f)  Download maps from a computer into your handheld satnav and follow a route in real time.
   .   
4  The accuracy of the signals picked up by handheld satnavs used by walkers is generally 5 metres or better for 95 per cent of the time.

5  There are two supplementary systems that receive satellite signals and improve their accuracy for use in civilian handheld satnavs. These Satellite-Based Aug- mentation Systems (SBAS) use a network of ground-based stations in fixed locations to calculate the locally-received errors. Corrections are transmitted to the satellites which then broadcast the corrected signals to handheld satnavs
   •   WAAS (Wide Area Augmentation System) which covers the United States and Canada
   •   EGNOS (European Geostationary Navigation Overlay Service) which covers Europe and the British Isles and extends for hundreds of miles into the Atlantic and as far north as Greenland
   
6  WAAS, EGNOS, GLONASS and BDS are compatible systems. Providing that your handheld satnav is either WAAS or EGNOS-enabled then accuracy is likely to be as good as 1·5 metres for 99 per cent of the time. Note that most handheld satnavs are manufactured by American companies which means that when setting one up for the first time you can normally only specify WAAS in the menu option. However, when specifying WAAS in European countries you will automatically be tuned to EGNOS.

ianj37

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Re: Handheld satnavs and GNSS
« Reply #1 on: August 22, 2015, 12:01:54 PM »
Hello Hugh

Obviously I can't help with this as it was me that raised the query, but excellent news about the sales of your book!

For anyone joining this topic my point was that whilst I accept that many of the 'newer' models of handheld satnavs (e.g. Garmin GPSMap 64) can get GLOSNASS my Garmin GPSMap 62s (still many around) can't and as mention of GLOSNASS is suspiciously absent from the spec of my SatMap Active 12 (current model) I suspect that this also can't pick it up.

Ian

Hugh Westacott

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Re: Handheld satnavs and GNSS
« Reply #2 on: August 24, 2015, 06:50:34 AM »
Thanks for that, Ian.

I'm coming round to the view that the easiest way to deal with the problem you have raised is to alter the passage in red to read

Note that signals from all four systems are compatible and can, depending on their age and level of sophistication, be received by satnavs, smartphones etc. Other countries are also developing navigation satellite systems.


Hugh

Lost Soul

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Re: Handheld satnavs and GNSS
« Reply #3 on: August 24, 2015, 10:18:52 AM »
Hi Hugh,

The subject of compatibility and interoperability of Sat Navs and the various satellite constellations has been the subject of some debate at various time on this forum.   I think your proposed note is about right.  Might I suggest that you try and elicit a response from Captain Paranoia.  He seems to have extensive knowledge on these matters.

Congratulations on your sales figures.

Regards

Lost Soul.

Hugh Westacott

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Re: Handheld satnavs and GNSS
« Reply #4 on: August 24, 2015, 11:25:36 AM »
Thanks, LS!

I have to admit that I have struggled with this chapter because it is an aspect of walking about which I know very little.

Also, it is the one subject that is dynamic and constantly developing and thus does not readily lend itself to book format. So all I can do is to discuss the subject in general terms. I’m glad that Ian pointed out that I was being too prescriptive and I’m pleased that it now seems about right.

I’ve contacted CP but I guess he’s on holiday in some exotic location.

Best wishes

Hugh
For a preview of the 5th edition of my book The Walker’s Handbook; Everything you Need to Know about Walking in the British Isles click here. Then click on ‘Reviews of The Walker’s Handbook' in the Navigation panel to the right of the illustration of the cover. 
 


Hugh Westacott

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Re: Handheld satnavs and GNSS
« Reply #5 on: August 24, 2015, 02:26:18 PM »
Thanks to whoever was responsible for resurrecting this thread!

Hugh

Lost Soul

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Re: Handheld satnavs and GNSS
« Reply #6 on: August 25, 2015, 12:57:18 PM »
Hi Hugh,

Your link to the book reviews, "here", doesn't work.

LS

captain paranoia

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Re: Handheld satnavs and GNSS
« Reply #7 on: August 25, 2015, 08:42:04 PM »
Here are my comments.

> The Global Navigation Satellite System (GNSS) refers to the system of circulating satellites

There isn't a single GNSS; there are a number of systems, each of which uses a different signal and data protocol. They are designed not to interfere with each other.

> Note that signals from all four systems are compatible and can be received by most satnavs, smartphones etc.

As above, the different systems are not interoperable, and need a receiver capable of receiving and interpreting each of the systems. The receiver will be able to combine all signals it can can receive into a single fix.

GPS and GLONASS are the two systems most commonly available on smartphones. Expect BDS to grow in use due to Chinese dominance in consumer electronics manufacture, and their rapid constellation launch programme.

> WAAS, EGNOS, GLONASS and BDS are compatible systems.

WAAS and EGNOS provide corrections for GPS only. They can not be used to correct BDS or GLONASS.

> Providing that your handheld satnav is either WAAS or EGNOS-enabled then accuracy is likely to be as good as 1·5 metres for 99 per cent of the time

For a free-space environment. SBAS knows nothing about a local, ground-based environment, and so cannot be used to correct for multipath or reflection errors. These can cause significant position errors (10s - 100s of metres) in mountainous and high rise urban environments. Outdoor users must remain vigilant for these errors.

Hope this helps.

captain paranoia

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Re: Handheld satnavs and GNSS
« Reply #8 on: August 25, 2015, 08:44:22 PM »
> for the 2nd impression, I'm taking the opportunity to correct one major factual and elementary error, and a couple of typos.

I missed this. Send me a doc or PDF of the chapter and I'll cast a more considered eye over it.

Hugh Westacott

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Re: Handheld satnavs and GNSS
« Reply #9 on: August 26, 2015, 05:57:40 AM »
Thanks, LS!

I hope that this provides the correct link to the reviews.

 For a preview of the 5th edition of my book The Walker’s Handbook; Everything you Need to Know about Walking in the British Isles click on http://walkwithwestacott.com. Then click on ‘Reviews of The Walker’s Handbook' in the Navigation panel to the right of the illustration of the cover.

Hugh

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Re: Handheld satnavs and GNSS
« Reply #10 on: August 26, 2015, 10:06:12 AM »
Hi Hugh,

Thanks, useful reviews you seem to have hit the nail on the head.

LS