First, you need to get your mind wrapped around the fundamentals of navigation. Navigation is a lot more than just using an electronic chart display system. You won't learn it overnight, either. You must apply yourself. It is roughly the same level of involvement as
learning a new language.
I suggest three purchases right off the bat for your self schooling: a paper chart of your area, a kit of
instruments containing a pair of triangles with protractor marks, dividers, a quality eraser and pencils, and a globe.
Why a globe? It illustrates in a very clear way the relationship between Latitude and Longitude, and why a degree of Latitude is the same distance anywhere, but a degree of Longitude is not, even though your mercator chart seems to think so. It helps you to understand that a flat chart is an approximation of the real world. It helps you to understand the geometry involved in Rhumb Lines, Great Circles, etc.
The paper chart and charting tools will give you a much more intimate knowledge of how a chart works. It is concrete. Well, it is paper, but it is a real world thing that you can touch and feel and see, and mark with waypoints and course lines and bearings and such. It has no video
game vibe to it.
Do not confuse Navigation with Piloting. When you can use landmarks or bouys or daymarks or
water color or visible shoaling for determining where you are, you are piloting. When you are out of sight of land and using electronic or celestial means of determining position and comparing them to your DR track, you are navigating.
A good early purchase once you have a handle on charts, set and drift, variation/deviation, etc is a
sextant, either used and of good quality, or a new plastic one. Personally I would recommend a used Plath but many here will tell you that a plastic Davis
sextant is fine. My reason for going with a more professional grade instrument is that the instrument error in plastic sextants can be large enough to hide small computational or table lookup errors, and you will sometimes not know when you have made a mistake. With a more consistent instrument, small errors stand out like a smashed thumb.
The logical way to LEARN navigation is to learn the basics first. That means celestial. Do not let anybody mystify this for you. It is not black magic and does not require a genius level intellect to understand it. Start with the more primitive techniques. Before there were accurate chronometers and
radio time ticks, Longitude COULD be found, but the methods were a bit tedious and required considerable mathematical prowess to pull off. Latitude, OTOH, was pretty simple. At least is was pretty simple once a day. Well, three times a day if you were in the Northern Hemisphere and could shoot polaris. But a noon sun shot taken at Local Apparent Noon is a dead simple way to determine Latitude. Sailors of old would sail to a Latitude and follow it to a landfall, and rely only on DR for approximate Longitude for days or even weeks of
passage. And that reminds me... actually your DR is the most basic navigational tool, but that will become quite obvious as you study. Anyway, if you look at your globe and imagine a sun out there you will see how when the globe is turned so that a given point is most closely positioned under the sun, so that the sun is exactly North or South of the position, the height of the sun can tell you your Latitude. So this is obviously the first thing to learn as you dive into the big kid's pool. We call this taking LAN, and it simply means determining your Latitude at Local Apparent Noon, when the Sun is at its highest point. The sextant does nothing except measure the angle between the horizon, you, and the celestial body which in this case is the sun. So actually pretty simple, right? There are some refinements that make this actually work with a practical level of accuracy, but that is the gist of it.
A bit more involved is taking a sight of a body, be it Sun, Moon, Star, or Planet, and reducing it to al LOP, Line Of Position. Still not hard. Anyway at the time of the sight, your position is somewhere on that LOP. If two LOP's taken at the same time cross, your position is where they intersect. You can not, obviously, take two sights at exactly the same time, but you can advance or retard them to a specific fix time, and the intersection is your fix, for that time.
You might ask why one doesn't simply take a sight and solve it for Longitude, and that is a good question. Quite simply, the azimuth/intercept method of calculating and plotting an LOP is more universal and more accurate. When you understand the Celestial Triangle, you CAN directly calculate a Longitude, if you have accurate time. And if you do NOT have accurate time, you can find it, and your Longitude, through methods that take advantage of the different speed of the moon compared to the motion of the stars, to figure out what the time must have been when the observation was made. This is then compared to the time of your clock, and a correction can then be made, so that Longitude can be found. Longitude is directly related to time.
There are tons of
books on the subject. I just wanted to demystify a bit and illustrate how much you can do with just the distance above the horizon you observe a celestial body, and maybe an accurate time reference.
Celestial Navigation can be cumbersome at times, yes. But it is the basis upon which all Navigation is rooted. And it is the ultimate backup to electronic methods. The backup function alone is worth the time spent
learning it. Sattelite or Terrestrial Systems CAN be hacked or just fail, even though this has (seldom) happened. Your
electrical system CAN have a catastrophic failure leaving you in the dark and with no means of
charging your devices. And the
depth to which you will have learned geography/cartography/geometry will give you an entirely different perspective on what your little electronic gadget is telling you. If all you know is to turn on a
screen and follow the arrows, you are no navigator and you do not know navigation, and you are not properly prepared for an ocean voyage. Period. OTOH, if all you have onboard for determining your position is a sextant and tables, you are not being very prudent or practical. As long as it works, and
GPS and other systems pretty much always do, it is usually accurate, often within FEET, not miles. Sometimes that doesn't matter at all, and two mile accuracy is quite good enough. Sometimes it matters a lot, though if it is that critical, maybe you are skirting a bit too close to
danger. You should ideally be in pilotage mode by the time your position is that critical. Anyway, the complete navigator is comfortable with both Celestial and electronic navigation, and always keeps a DR track on a paper chart, paper plot sheet, or electronic chart display, preferably both paper and electronically. Small boats have little space for spreading out charts, but once you understand Navigation, you can easily and quickly construct a plot sheet for your Latitude on any size paper you like, even standard printer paper, and keep your DR on that. Your DR is your absolute fallback system. DR is Ded Reckoning, short for Deduced Reckoning. You take your course and speed and time and construct a track. Simple. When you have a fix, you can compare and see what your set and drift are, and correct for it. If for some reason you cannot get a fix, you have a fuzzy sort of idea of where you are and where you will be an hour or a day from now, and it is a lot better than just guessing.
The most basic universal law of Navigation is that you never rely solely on one means of determining your position. The prudent mariner simply does not do that.
What they said about oeSENC and OCPN. Good system, flexible, not
hardware dependant or OS dependant. You can run OCPN on your WinDOHs
desktop, your Ubuntu
laptop, your Android tablet or phablet. And it just works. Did I mention it is free? That should count for something, especially if you already feel bullied into dropping $400 on a used Plath sextant LOL! A pity the whole world doesn't recognize the public benefit of universal free charts. The thinking of most governemt hydrographic agencies is that the user should ultimately pay for the
service of surveying, compiling, and publishing charts, but it is IMHO in the public interest that mariners know where the hell they are, especially in relation to ecologically sensitive areas or
reefs where vessels can wreck and spill
oil, stuff like that. Well, I can't argue with governments that do not give me the
power to vote, so nothing I can do. The US does have free charts for all US waters and that is one thing that I can praise the powers that be for using common sense. Anyway, yeah you are kind of stuck with paying for your charts in Australian waters and you are just gonna have to suck it up.
CM93 is a valuable tool, but of course out of date and therefore unreliable in very near coastal or inshore waters. It is good for voyage planning. It is good for ocean passages well away from islands or reefs. It is widely available for download and yeah it is copyrighted, but because it is out of date and has limited utility, the owners don't seem to be going after folks who will after all, be exposed to the product and maybe become customers. It will also give you something to play around with while you learn to use electronic chart display systems such as OCPN, which plays this portfolio quite well.
GE2KAP is a great toolset. Sometimes a
Google Earth shot reveals shore and bottom structure that is not obvious on official charts. When you can create your own chart from such
images, you have another great tool at your disposal. As an example, look at the available chartage for San Pedro Entrance, through the
Belize Barrier Reef. There are no permanent markers showing the channel. Not on the charts, not in reality. Sometimes you can eyeball your way in pretty good. The channel is about 200' wide, for small boats, but there is a hard turn just inside the barrier reef, necessitated by another bit of reef, and if you turn too soon or too late, you are screwed. You can start in with the sun high and at your back, but find that once inside, you can't see the bottom very well, and there are a few deep
coral heads that will fool you and make you think it is time to turn NOW... A georeferenced Google Earth
satellite shot in OCPN is a valuable backup tool in shooting this inlet. (JUST DON"T STAY GLUED TO THAT SCREEN!!!!!!!!!!!!) And there are countless other spots where a God's eye view in full living color lend an extra perspective to the official charts. Also, if you find yourself with out of date and uncorrected charts, (Really... what yacht skippers actually update their charts with official corrections?) bars and banks can move. A lot. Especially when there has been a
hurricane or tsunami or similar catastrophe.
The crowdsourced movement has a lot of potential, but it hasn't really taken off in a big way yet. When EVERYONE pitches in with a system that automatically records hydrographic information and submits it to a central database, we will be on our way. Right now, we don't really have that. So data is spotty, and nearly useless. Right now for practical purposes I would say it is nothing more than a REALLY GREAT IDEA that I would love to see become a thing.