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With the continuing commercial development of SatNav systems for vehicles and hand held devices the user community among the general population is rapidly increasing. There is a requirement for more awareness of how these devices work.

Many have a strong belief in the accuracy of GPS and the maps that are supplied to manufacturers of SatNav systems. This belief is well founded for nowadays GPS has a high reliability. However GPS and the maps are not without fault. As with any technical development there are issues and problems that can occur both while in use and in development.

When I hear some people talk about GPS I feel that they do not really know much about their satnav system. The freely used term 'I have a GPS' is without regard to the GPS bit only being a part of a complete integrated system with all the different parts needing the other. It is as though most believe, because GPS is space stuff, that understanding is beyond them. This is not the case. GPS technology is deeply engineering, but, the essential principles can be well understood with only a slightly above basic knowledge. The same applies to the navigation and mapping principles that all go together to get you, in your car, from A to B, or Z. When it comes down to general principles this technology is not the rocket science that it would first seem to be.

GPS systems have varying accuracy, according to make and cost and also whether moving or stationary. Further degradation in accuracy can occur depending on your location and present circumstance of use. Setting up the complete nav system at the manufacturer end also has its problems, for the end result requires a map on a flat screen. The process of going from round earth to flat has its difficulties. Then there is the issue of keeping maps updated as changes in road systems occur.

These systems are a fantastic technology but they do have limitations. Being lost or just misplaced can carry a risk factor with severe consequences in some harsher environments. I guess we have all heard some examples of, shall we say, the dafter misidentifications through using car satnav.

To this end this site presents the downloadable 100 page with many diagrams guide:


The SatNav Users Guide to Navigation and Mapping Using GPS



It's a clickable link but you may need to read on to see if you think it's useful for you. There is a buying info click link at the end of this page.

The Guide provides information on how these systems work covering aspects of GPS, how we go from round to flat and allow for our local area, how digital maps are made and how they are used to navigate along roads from A to Z.

It is intended for the SatNav user who wants to know more about how GPS, navigation and mapping combine together to give us these systems. It is a behind the scenes information and awareness for those with an interest in understanding more about what is involved, the difficulties encountered and some misconceptions that are around. It is not a guide to particular systems or how to use them individually. It will not, directly, help you to not get lost. There are other books for not getting lost, involving map and compass. It will help you to understand where things can go wrong, how to notice them and correct them, or at least to know not to rely on it for the moment. It will also give you an edge over those who think they know but really don't.

So, this technology is fantastic, but, it is designed and built by humans. Mistakes and errors are human nature. Do not fall for others' human nature. You can help yourself to avoid this by understanding how systems work.

You input your destination correctly, but, the software misinterprets or glitches and calculates an inappropriate route. The map may be not updated. If followed blindly, unchecked, it may not be disasterous, but is likely to lose you time, fuel, patience and, perhaps, temper.

Blind following has been done, hence those weird and strange incidents of bridges that really are not there. Jetties that are roads across oceans! OK, obvious (to most) extremes, but, some errors may not be so obvious. Armed with information you are better qualified to look out for them. You can develop a feel for when things can go wrong and check. Stand back and take a broader look, or, resort to a paper map. As an overview they are still valid. Some may be more up to date than satnav maps.

Does it look right?

The technology does not anticipate for peoples' sense and appropriate judgment. This is for you to do.

Knowing more about how the systems work can help you avoid the patience and temper situations.

Knowing the complexities involved, even just basic knowledge, in getting these systems into operation will aid you to understand how errors and faults can arise and instil in you that 'Does it look right?' mode.

I have always believed that you can say you are good at something if you know what you don't know. 100 pages cannot cover everything of all the included subjects. It will give you enough understanding of what is generally going on for your SatNav use and where to dig deeper if you wish. It is not the full story, each section could be a book in its own right. It does cover slightly more than what many consider the basics. It will certainly give you an advantage over others who claim to know or to have the best system. For anyone about to embark on a course of study I would class it useful as a first year graduate starter information.

I say 'slightly above basics' and not 'deep rocket science', however, complete explanation is difficult if the technical is largely avoided. This is the nature of the game, for nature is cruel. To get a reasonable grasp of understanding, nature requires us to think in 3D and adds awkward irregularities on top. Nevertheless, it's the sort of subject that full deep understanding is maybe only required by those who are paid to do it. The info here will leave you with a good grasp and awareness of the concepts that will help you understand these systems more and put you ahead of many.

These misconceptions about GPS and SatNav maps, well they may lead you astray. It may be likely that some salespersons have these misconceptions and general uncertainty about some details.

'How does it work?'

'It gives you an exact position any where in the world.'

'Exact, really, anywhere? Ok so how accurate?'

'Very accurate.'

'Give me a figure.'


'Based on what?'

'What? It's just accurate to 5m.'

You can beat him. If he cannot answer your accurately guided questions, maybe you can get a discount. This guide will give you the information.

Remember though, the salesperson may also have read it.

Another accuracy item. I often hear about pinpoint accuracy. Now what does that mean? To me pinpoint is less than 1mm, er, like maybe the point of a pin or needle. Yes, a very expensive and sophisticated GPS receiver can achieve this if left standing in one place for 24 hours plus. No doubt about it though, 5m is actually good and can reasonably be expected, but 5m is not pinpoint.

The topics covered:

1. What GPS Is. The 3 segments.

2. How GPS Works. Positioning method, the signal, its codes, time and error sources.

3. Augmentation Systems. Methods to further increase accuracy.

4. What Does Accuracy Mean? Well, what does it mean, really?

5. From Round to Flat: Projections and Datums. What they are and how and why they are used. Datums is the correct spelling.

6. Making Digital Maps. How satnav maps started. Map structures and databases. How the system gives route navigation instructions.

Appendices. Some of us who went into this as a line of work unfortunately realised too late just how horrible the sums are. Formulae and further explanations of some aspects are included for greater awareness but are separated and shoved into appendices. For the brave.

Snips from each section are in a pdf preview. This also acts as a test to ensure you have Adobe Reader on your computer. In the, nowadays, unlikely event you do not have Adobe Reader, here is the free download link.

The guide has been put together from my knowledge in the field as a navigator, surveyor and mapper, offshore, coastal and onshore. It is backed up by research in some specific areas to update myself. I have found a lot of free content on the internet. As with many technical topics it requires much digging to find what you think you want, and then, is the info reliable? Again, knowing what you don't know. This, you can also say of this guide. I may not have explained the exact techniques used within Section 6, for example. These would be company secrets so I couldn't tell you even if I knew the detail because I worked for them, which I do not. The principles are there. Again, for those interested this guide saves you the search time.

The content is reasonably technical. Whereas I have attempted easy explanations in ways not done by any conventional methods I have so far come across, it may in the end not be for some. For the $7.99 I am asking for the Guide there is a 60 day refund period.



For further buying information press the compass rose below to start navigating

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John Maris 10 May 2016


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