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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 pinpoint 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 in my car" seems to be 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 with many diagrams guide:


The SatNav Users Guide to Navigation and Mapping Using GPS


For the satnav user to learn more about GPS, navigation and mapping 

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.


What the Guide Does

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 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.

There is quite a lot involved and the book covers it in a fair amount of detail. However, some of you may not want the whole detail so the pdf, which is the main idea, comes in two forms as a Basic book and an Advanced book. The Advanced is also available to download as reader formats. You can download your choice or all of them.


Error Alert!

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 and, perhaps, patience.

Blind following has been done, hence falling for 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.


Does it look right?

You can develop a feel for when things can go wrong and check. Stand back and take a broader look, maybe even look at a paper map. As an overview they are still valid. And remember, the Mark I eyeball is still a valid aid.

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

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.


Knowing What You Don't Know

I have always believed that you can say you are good at something if you know what you don't know. The book cannot cover everything of all the included subjects but 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.


Nature is Cruel

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, and 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, remove the misconceptions that abound and put you ahead of many.


In the Shop

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 pinpoint position any where in the world."

"Exact pinpoint, really, anywhere? Ok so how accurate?"

"Very accurate."

"Give me a figure."

"5 m."

"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.


Now, About that Pinpoint

We often hear about that 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.


Who Am I to Say?

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. This is stuff I need to know for the set up of the job and to make sure it runs to spec. I have had to hold up a survey saying "the nav is being naughty". Mind you, my expensive kit helps by giving me red warnings. I don't think many satnavs tell you GPS is 50m out.


Buying and Refund

Remember the book comes as two pdf versions, Basic and Advanced  and two reader formats. All for the one purchase. Whereas I have attempted easy explanations in ways not done by any conventional methods I have so far come across, it may still in the end not be for some. For the $14.75 I am asking for the Guide there is a 60 day refund period.


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

I wish you the joy of everyday not being lost.

John Maris 10 May 2016