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GPS is just great isn't it. We get an exact position anywhere in the world whenever we need it. Everyone knows, because it's often said, that it pinpoints us, gives us an exact position. Something we never had before.

Whoever invented it what a superb system they have given us. And I'm going to show you how good and clever it is. I will, but.....

Hang on, let's step back a bit.

First let's define 'pinpoint' and 'exact' for these are being used as accuracy terms and accuracy is a well defined concept but often very loosely used. Hey, I'm as guilty as anyone here. If it's good enough for you can it be called pinpoint? This could range from millimetres to kilometres.

Well Ok, but we've never had this accuracy before, have we? Yes we have. There are systems before GPS equally good, if not better.

So what's this all about?  As I said, I'm going to show you how good the system is. We wouldn't have it if it wasn't. I will show you how clever the design is to get you from where you are to where you want to go. As long as some things are understood. As with most things there are limitations and the nature of navigation systems, including those previous to GPS, means extra limitations due to the way and the environment they operate in.

Because it's 'known' to be so good I will suggest that many are complacent, over confident, with GPS and the satnav they have without understanding how it works and what the limits are.

You can see this in the GPS and satnav speak that's about. We've done pinpoint.

"I have GPS in my car". Yes you do. You also have a map and some software. You have an integrated navigation system running in a computer. It's called a satnav. There's a lot of stuff going on to put that dot on a map, as accurately as it can under the circumstances, and then get you to where you want to go.

"But GPS says I can go that way", Then why is everyone flashing you and honking horns?

Misconceptions, misbeliefs, over trusting?

Maybe the trust is because, let's face it, it's space stuff, rocket science and deep engineering. It is for those that make them. Out of my league here as I'm sure it is deep technology at their level. For us users there are basics to how they are of practical use that are not hard to get.

The aim here is to put it in perspective. We have a great system but it has difficulties in its operation. It works in a way to overcome those difficulties, to the best we can so far do. Knowing this you maybe even more impressed on how clever it is and also aware of when it's not so clever.

Bear in mind it was originally not for us but for military use. It is not a totally new idea but a development of existing systems. Where the advantage lies is that they made it global by putting it into space. They made it cheap enough to be more practical than existing systems and cheap enough now for the likes of us to get around accurately enough for our purposes. With the required due diligence. I don't think it's fair to blame the United States DoD if we drive into a river.

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 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! Can we really believe that these have happened? 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."

"Huh I dunno. 10m maybe"

"Based on what? Is that pinpoint then?"

"What? It's just very accurate."

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, 5 - 10 m is actually good and can reasonably be expected, but I'm saying that is not pinpoint.  We havn't agreed a definition yet.


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. Tech advances. 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 2019