Mobile phone GPS navigation – basics

Mobile phone GPS navigation – basics

Updated: 11/11/2019.

This is a work in progress – I’m translating the original article from Serbocroatian when I find the time – chapter by chapter. It will be finished. New articles will follow.

The main purpose of this article is to enable the reader to use other people’s routes, as well as to create their own navigation routes and to be able to “explore the unknown” by themselves. With the final goal to help people gain more confidence when hiking, or cycling in forests, or mountains, explore new areas. Not necessarily relying solely on GPS and technology.

This is a work in progress. Any additions, or suggestions on how to make it clear, comprehensive, yet as simple to read/follow as possible are more than welcome. Text you are about to read is a result of over a decade of experience with hiking and using all sorts of GPS navigation gadgets. The authors have done their best to offer a “digested” version – easy to understand, so that you can do it all by yourself with minimum effort. This, first version, took days, but it will be improved further, mostly in terms of making it more simple.

Contents:

  1. Introduction
    1.1. Basic idea
    1.2. Advice
    1.3. Beginning – what is our goal
  2. Basic terms
    2.1. Map
    ….2.1.1. Vector and raster maps
    ….2.1.2. Online and Offline maps
    2.2. Track and Route, Waypoint (POI, Landmark, Placemark, Midpoint), gpx and kml(kmz) file formats, Overlay and Layer
    ….2.2.1. About words (and how to further complicate in order to explain)
    ….2.2.2. Track
    ….2.2.3. Route
    ….2.2.4. Overlay and Layer
    ….2.2.5. Waypont (POI, Landmark, Placemark, Midpoint)
    ….2.2.6. File list in a folder, and view inside the database


1. Introduction

1.1. Basic idea

The basic idea of this manual is to, in as little steps as possible, set the base for planning a hike and its tracking on a mobile phone (smartphone). A base that can later be expanded in many different ways. It is written with the best intentions and I hope it will be helpful, but don’t blame the manual, or its author, or the place where you’ve found it in case you get lost in the woods.

For a start I hop you won’t get lost in the manual so at the beginning I gave a brief overview of the route that we’ll follow together (contents). Well go through this together and stop at several important and, I hope, interesting points. Through our hike, we’ll gather breadcrumbs of knowledge that will eventually, give a clear, full image.

If you are reading this on paper, feel free to underline things. That track will help you if you get back to this hike.

On our hike we’ll see a network of other paths that lead to broadening the knowledge, which we’ll only “touch” or cross roads with, but won’t be following this time, but we know they exist and can be explored.


1.2. Advice

This text turned out a bit longer than was planned and I’ll first like to give you one piece of advice for your and mine sake: don’t be afraid.

This advice is for you because everything you’ve really wanted to understand – you’ve managed, didn’t you?

But also for me, because it is an excuse that if you don’t make it to the end of this text, it’s not for my poor explaining, but because of you.

This manual will have two parts. First is theoretical and I hope it will give you the base for better understanding of everything that will later be demonstrated through a complete example. In the first part I tried to explain things in a way I would like to have had it explained to myself before I had figured it all out.

At the same time, I’ll try to make the example in the second part such that it can be done even without fully understanding the first part, for those that get discourage for any text longer than an average Tweet.


1.3. Beginning – what is our goal

I wish to take a hike through an area I’ve never been before. I’ve just got good will and a mobile phone.

  1. How to find and pick which route to take?
  2. Kow to translate that desire to a file I can transfer to a mobile phone?
  3. Which smartphone application should I use?
  4. I’d like to have, within the application, some map where I can see the terrain and my prepared route and, if possible, a network of routes that are at my disposal if I wish to make the hike a bit longer, or shorter than my initial plan.
  5. I’d like to, while I’m walking, see my current position, but also to see the track of where I’m coming from and be able to later record that and show it to the others.


2. Basic terms

2.1. Map

2.1.1. Vector and raster maps

Map will be the background that we’ll always have shown in our application and, depending on its quality (in terms of information) we’ll have more, or fewer details in it.

There are two types of maps: vector and raster.

Vector map is placed within a file inside which everything we need is written in a “mathematical” way. The size of that file is drastically smaller compared to a “raster set” that we would need to cover the same area – and I’ll explain why.

The word “mathematical” is used in a sense that when we zoom a part of the map, wanting to see a smaller area, but with more details, it contains all that’s needed to show this new level of details inside the one file where everything is written in a form of “mathematical formulas” in the map calculates what it will draw on our screen, while the image is always sharp.

Raster map is an image. It can really be a photo, like satellite photos of the earth, or it can be drawn. We’ll mostly use drawn maps on the terrain, but the process of zooming in and the reason why the term “raster set” was used above will be explained using satellite photographs.

Disregard physics for a while and imagine we are in a balloon that flies high above the Earth. Then imagine the Earth as a flat board. And we take a photograph of the entire, flat, Earth. Our photo will have as many pixels as the resolution of our mobile phone camera has. As long as we want to look at the earth as a whole, the picture will look nice.

Raster picture of the entire Earth
Raster picture of the entire Earth
Picture 1

However, if we want to see one part a bit better, closer, say Europe, what we can do is make one part of the entire Earth photo enhanced so that only Europe fits the screen. This, of course, will make the image very blurry if we want to zoom in further, to show Serbia for example – and even worse if we just want to show Fruška Gora mountain (near Novi Sad).

"Magnified" ("zoomed in") section of picture 1, showing Serbia and its neighbourhood
“Magnified” (“zoomed in”) section of picture 1, showing Serbia and its neighbourhood
Picture 2

Other option would be to put the balloon a bit lower and take a photo of only Europe. We would have a picture with the same resolution as the first one (as the camera resolution dictates), but now it covers only Europe, so it’s nice and sharp when we are looking Europe only. Zooming in to see Serbia and Fruška Gora would make the picture a bit less horrible, but still blurry.

So, the smaller area we wish to see in detail, we must go down, lower and take a photo of the same resolution, but covering a smaller area.

Zoom 1 - picture of the same resolution as picture 1, but showing a smaller area - nice and sharp
Zoom 1 – picture of the same resolution as picture 1, but showing a smaller area – nice and sharp
Picture 3

The task done by an application that shows us a map will not be to zoom in on the one, starting picture of the entire Earth, but to show us an image ideal for our desired level of zoom.

A small digression: what would be tempting, as an idea, would be to assemble all the images of Earth taken from the smallest height, into one huge image and then be able to zoom in as much as we like, but that image would be so large that, due to its size and the time needed for an application to process it, the image would be useless.

Let’s call the view of the entire Earth: Zoom 0. Zoom level that shows Europe and Asia will be Zoom 1.

So, for the entire Earth we need one photo. When we go to Zoom 1 level, the entire Earth will consist of 4 photos taken from a lower height (altitude).

When we go to Zoom 2, each of the 4 photos will be replaced with 4 new photos with more details. So, for Zoom 2 level we’ll have 16 images, while for Zoom 4 level we’ll have 256 photos in order to cover the entire surface of the Earth (at the desired level of Zoom).

Each additional zoom level divides the given picture into 4 smaller ones
Each additional zoom level divides the given picture into 4 smaller ones
Picture 4

Maps usually have a maximum level of Zoom 18. For our needs level of Zoom 16 will be enough (minimum 15, maximum 17). What this means exactly will be explained in the chapter about Offline and Online maps.

And here’s one deliberately imprecise and oversimplified comparison:

Vector map of the entire Earth would take all the memory of a smartphone and its processor would be just fast enough to process it (zoom in and out).

In order to download all the layers of a raster image for the entire Earth (i.e. millions of smaller images from various areas on all the 18 Zoom levels), it would take 1000 times larger memory, but the processor could be 1000 times slower because, to remove one small image and replace it with another is not a difficult task (that is why we’ll always download only the map parts that are of interest).

If we had one raster image of the entire Earth, it would take half the space than having it divided per levels of zoom, but also 1000 times faster processor because it is very difficult to process such a large image (so that option is out of question).

Map that we’ll use in our example will be drawn, not satellite image (or balloon one), but the principle is the same.

2.1.2. Online and Offline maps

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