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Sampanviking
2011-Apr-13, 10:42 PM
Maps are a particular interest of mine and I have given quite a bit of thought to the problems of trying to map the Milky Way. I share these thoughts with you and hope they may be interest or even use.

Exploration and Map Making goes hand in hand, if for no other reason that it is the record of the exploration being carried out in the first place. Fortunately however the needs and benefits of accurate maps have their own imperative and so the expansion and improvement of maps and charts remain an important and ongoing human activity.

Cartographers are some of the first humans to “leave the planet” and maps already exist of other rocky planets and moons with a wealth of new worlds and improvements waiting to be undertaken.

The real challenge however must be to map the stars themselves. This is not by any stretch an easy task and throws up some very unique challenges.

Maps of the heavens are of course not new, but they are very basic and arguably not really maps or charts at all. The vast majority of our maps are the Stella Equivalents of standing on a hill and drawing a picture of the horizon. In effect they position the map maker at the apex of the view and look out in all directions They are correct but contain little useful information in a cartographic sense.

The more typical map we have today takes an overview of the centre and projects its image as a tableau around that point. The first question of course is where the centre of a map of the Galaxy should be and the obvious and correct answer should be the centre of the galaxy itself. This is fine in principle, but given the inability to detect and record accurately more than a small percentage of the stars in the galaxy, this is impractical and would produce maps of little value.

Clearly then we still need to concentrate our attention to those areas we know/can see best and reference our work to the position we know and understand best. This is of course means projecting maps of the starts in our proximity using the Sun as the Centre.

Every map should be orientated and Galactic maps should be no exception. Fortunately the milky way has two poles and a equator and so orientation is quite straight forward putting the viewer above the sun directly in line with the Galactic Centre.

There is also the matter of projection, which is always a problem for terrestrial cartographers who usually have been required to project a 3 dimensional globe onto a 2 dimensional rectangle. The problem for an Astro Cartographer will of course be very different and vary considerably based on the kind of information which the map attempts to present.

This of course is a good place to introduce the problems.

Mapmakers are one of the fairly rare form of scientist, whose raw product is intended for consumption and use by the layman rather than a fellow professional. This means that the vast majority of end users are only interested in the final product and wholly disinterested in how it was produced.

This means that a map has to be user friendly and Galactic Maps are going to be no exception. As human beings we love shapes and relate to them very easily. A map of the earth is instantly recognised at a high scale on account of the shape of the continents and even young children quickly can become good at recognising bits of Continental shape and relating them to the overall picture.

Our response to the Stars in no different and our first ever astronomical task was to pick out patterns in the Stars and name them. Most of us I am sure still navigate our casual star gazing by picking out the constellations. This of course only works because we are looking at a two dimensional representation of a three dimensional space and doing so from a fixed perspective. Any galactic map in the modern media is going to be three dimensional and with unlimited perspectives.

Shape also gives other benefits. The shape of the continents allows us to then zoom in and examine smaller areas in greater detail. One of the great advances of digital science is that you are no longer restricted to a map at just one scale. Now different maps at different scales are bundled together giving the full range in many places, from Global Atlas to local street map. If you get lost you just zoom out until you find a shape you recognise again.

Well the same principle must surely apply to the Galaxy and at the highest resolution it does. Fortunately the galaxy is an discreet object with noticeable structure, which is just what we as a species like. It’s a memorable shape, easily recognisable and not to difficult to differentiate from other Spirals (in representation), once you take the trouble to study it.

The problems really begin however once you try and add structure.

The most true and accurate form of representation is of course to record the co-ordinates of every single star in relation to the Galactic Centre. Sadly this is a task well beyond our abilities to observe and measure and so we would have to content ourselves with the Stars in our immediate vicinity centred; as previously stated, around the sun.

Such a map would be very accurate, but how does it rank in terms of its user friendliness? Not very well is the honest answer as a mass of countless points in a vast swathe would be a bewildering array of objects that would in all likelihood prove themselves un-navigable. Funnily enough of course a set of co-ordinates are the raw data that cartographers use to prepare maps and very early maps such as those by the Classic Egyptian Cartographer Ptolemy presented his navigational maps as books of co-ordinates rather than as graphic charts. The fact that this method of presentation has not stood the test of time, rather speaks for itself.

So we can produce a perfectly accurate map of star co-ordinates and also incorporate other local details of the star and any exo-planet system and it would be largely unusable.

Well you can start looking for a solution by going once again back to basics.

When we look at a map of the Earth we see not only shapes but also Geography and we give this Geography names, usually starting at a Continental level and then zooming in to nation states, provinces, counties, Cities etc etc, not to mention natural features of the landscape such as Mountains, Rivers and Hills. This naming process means that not only can we recognise shapes of Geography, we can also describe them succinctly and precisely. If we like shapes we love names and putting the two together is our most powerful navigational tool.

This means that we must consider issues of scale and appreciate that detail must mean different things at different levels of resolution. It also means that we must become better at defining the Geography of the local Galaxy and more used to using it.

Two main solutions present themselves, neither of which are perfect.

One – simply slice up the local galaxy as a three dimensional layer cake and deal with the individual and uniform sized sections.

Two – look for natural structure in the region as defined by the underlying gas and dust bubbles in which most stars are naturally grouped.

Solution one is probably the easiest to construct but is prone to the same problem as just preparing a vast star chart, as one section can easily become indistinguishable from another and ultimately overwhelm the senses of the end user. It’s also in a sense a bit like the European Imperial borders drawn for Africa. Useful bureaucratically, but taken without regard for the underlying geography itself.

Solution two can work well when there is good structure at that level of detail but is vulnerable to having vast swathes with little to distinguish it from any other.

Personally I see a solution that combines the key elements of both.

The basis of this geography would be to define regions of space by their distance from the sun using a set of concentric spheres, probably at about 10 parsec intervals and each layer given a specific name. Into these spheres I would overlay the natural structure of the galaxy and use it to determine discreet regions which again would be specifically named.

These simple actions reproduce in the Space around us, a Geography which is the equivalent of terrestrial continents and countries. It has visible and identifiable shape and it is named, which are the very factors which we recognise and respond to best.

It also does something else, it starts to promote the notion that we are not just an Island Solar System but part of a local group of stars which themselves relate to other nearby groups. This is important, as it is this that gives the geography context and meaning.

Once the rings and regions have been defined it will be possible to subdivide the larger areas into sections – the States or Provinces of Space and these too should be named to give them a sense of individual identity. Needless to say the name of the brightest star within any individual section, should be a prime candidate.

Finally within the sector there are the individual stars themselves – the cities of Space, which can then be presented with all the required or available level of detail.

This of course brings us back to the matter of the projection, or how the information is displayed. Is still not an easy question to answer and I suspect that multiple projections will need to be produced, to provide a variety of viewing experiences and ultimately, it will be the end user who determines through use and experience, which are the most useful and useable.

Not surprisingly, I am not the first person to have spent time wondering about these problems and some have already produced websites to showcase their solution. The best I have found to date is called 3D Galaxy May
http://www.3dgalaxymap.com/Galaxy/

This site bases its solution more about option 1 – many different sections and can be awkward to navigate, but does contain excellent graphics and plenty of good information.

I would be pleased to hear comments and suggestions on these matters and would also be interested in any other websites you know which have tried to solve the mapping problem.

Nereid
2011-Apr-14, 03:29 PM
Isn't any judgement on how user-friendly a (galactic) map is dependent on who the users are?

neilzero
2011-Apr-14, 03:44 PM
It would be expensive, but I think we can duplicate most of the visual features of the holideck of original Star Trek. Clear representation of a three dimensional star field is confusing on two dimensional paper or a computer monitor. ie I have little idea how far Barnard's star is from the Centauri system. Likely between 3 and 10 light years. Neil

Sampanviking
2011-Apr-15, 07:06 AM
The end user is going to be the ordinary guy, while the idea is to produce a graphic representation of the near galaxy (up to around 500 - 1000 lty away) which is as iconic and memorable as the classic Mercator Map of the Earth, which every school boy grows (or at least grew) up with in his Atlas.

This means producing an map system that not only can be used as a concise 3D computer model, but which can also be reduced to a 2D image for Atlases and Wall Charts.

The intended result is to give the sense a real sense of belonging and place in the local galaxy rather than as being an Island separate from it.

Reproducing Individual Stars at this scale is just not practical, but representing them through Clouds, Bubbles and original Nursery Groups etc will be. Another analogy is perhaps Island Archipelago's where we deal with large groups of Islands as a single entity etc. This means including the Sun with its local "archipelago" and building up the map progressively with the neighbouring ones.

kzb
2011-Apr-15, 03:55 PM
http://wise.ssl.berkeley.edu/index.html

WISE data preliminary release, "millions of new objects" ..go to it !!

Nereid
2011-Apr-15, 08:22 PM
The end user is going to be the ordinary guy, while the idea is to produce a graphic representation of the near galaxy (up to around 500 - 1000 lty away) which is as iconic and memorable as the classic Mercator Map of the Earth, which every school boy grows (or at least grew) up with in his Atlas.Apples and oranges?

The classic Mercator Map of the Earth is of a 2D surface; a graphic representation of the our region of the Milky Way (out to ~1 kly) would have to be 3D.

So perhaps you could start by asking what map/graphic of a 3D entity/region is iconic and memorable (at least to every school girl)?

Sampanviking
2011-Apr-16, 08:45 AM
Apples and Oranges ? Yes and No I suppose.

The World Atlas is of the 2D surface of a 3D sphere projected onto a 2D rectangle, which; although not easy, is a magnitude of difficulty less than projecting the 3D volume of a sphere in the same way.

Further, the Earth Surface is a finite quantity and while we can enhance the detail of the existing surface, no new surface is going to added on to what we already have.

Iconic in this instance may have to mean a memorable method of design/presentation rather than projection in the strictest sense, especially if the structure of the local bubble does not lend itself to memorability.

My best guess at this point would be a series of outfolding planer projections (probably compressed) to show sections through the key axial planes.

This would also reinforce the importance of designating different zones of distance from the sun, as; If you had these projections opening up around a central core, you would have the option to produce a series of charts which work rather like a Russian Doll, with all previously expanded space contained within the next central core.

Could be enough to transfix even the most truculent of school age hermaphrodites.

Hornblower
2011-Apr-17, 09:34 AM
The end user is going to be the ordinary guy, while the idea is to produce a graphic representation of the near galaxy (up to around 500 - 1000 lty away) which is as iconic and memorable as the classic Mercator Map of the Earth, which every school boy grows (or at least grew) up with in his Atlas.

This means producing an map system that not only can be used as a concise 3D computer model, but which can also be reduced to a 2D image for Atlases and Wall Charts.

The intended result is to give the sense a real sense of belonging and place in the local galaxy rather than as being an Island separate from it.

Reproducing Individual Stars at this scale is just not practical, but representing them through Clouds, Bubbles and original Nursery Groups etc will be. Another analogy is perhaps Island Archipelago's where we deal with large groups of Islands as a single entity etc. This means including the Sun with its local "archipelago" and building up the map progressively with the neighbouring ones.




Apples and Oranges ? Yes and No I suppose.

The World Atlas is of the 2D surface of a 3D sphere projected onto a 2D rectangle, which; although not easy, is a magnitude of difficulty less than projecting the 3D volume of a sphere in the same way.

Further, the Earth Surface is a finite quantity and while we can enhance the detail of the existing surface, no new surface is going to added on to what we already have.

Iconic in this instance may have to mean a memorable method of design/presentation rather than projection in the strictest sense, especially if the structure of the local bubble does not lend itself to memorability.

My best guess at this point would be a series of outfolding planer projections (probably compressed) to show sections through the key axial planes.

This would also reinforce the importance of designating different zones of distance from the sun, as; If you had these projections opening up around a central core, you would have the option to produce a series of charts which work rather like a Russian Doll, with all previously expanded space contained within the next central core.

Could be enough to transfix even the most truculent of school age hermaphrodites.


I cannot imagine an ordinary-guy end user, without special training, being able to make much visual sense out of a static display of side by side cross sections as you appear to be describing. These charts would not have the sort of straightforward visual correspondence to an actual view of the sky that a map of the streets around a tall building has with the view of the same streets as seen from the top of the building.

If I wished to transfix a bunch of potentially truculent youngsters, I would superimpose the cross sections in a computer to simulate the actual view from the original viewpoint. Then I would start moving the viewpoint around to drive home the 3D perspective effects.

For starters I would put up a display of the sky around Orion and introduce enough lateral motion to cause Sirius and Procyon to shift back and forth several degrees. That would cause Aldebaran to shift noticeably relative to the background Hyades stars, but leave the cluster otherwise little changed. The remote luminaries of Orion and Canis Major (other than Sirius) would remain nearly fixed. This would be a whizbang display that should appeal to many youngsters, and could be related visually with relative ease to what they would see when riding in a car past a nearby sparse forest with a remote mountain range in the background.

My next exercise would be to back up by about 100 light years. Now Sirius and Procyon would converge into Orion and fade with the increased distance. Aldebaran would do likewise to a lesser amount, the Hyades still less, and the Pleiades less than the Hyades. Orion, with its bright stars already several hundred light years away, would be shrunken and somewhat distorted, but still generally recognizable. Meanwhile, nearby stars which started behind us would enter the field of view from the sides. If we backed off in just the right direction, Barnard's Star might whiz by at close range.

Now let us go in a big circle around the core of M42. After a quarter of a revolution we would have a side view of Orion, and the pattern would be distorted beyond recognition. At the same time numerous lesser stars which had been too faint for naked eye viewing would be nearby bright features of the new sky.

Of course, trying to view every star in the galaxy this way would require a prohibitive amount of computer power, even if we could somehow measure the positions and distances of everything. My idea would be to map the larger scale features, and then add plausible ordinary stars with some sort of a random generator to give the viewer an idea of what the view would be like if they were real. The digital projector at the revamped Hayden Planetarium in New York does something along those lines.


snip...

The intended result is to give the sense a real sense of belonging and place in the local galaxy rather than as being an Island separate from it.

...snipI think my idea would accomplish that very nicely. Just include the Sun in the original scene, and watch it recede and fade as we dash away from it. That would put it in perspective.

Noclevername
2011-Apr-18, 12:57 PM
How about a Galactic Map App for their phones? That seems to be what they pay the most attention to these days. Make a game out of it: "Find your way through the Galaxy" or "Milky Way Scavenger Hunt" or something like that. Repetitive play could make them very familiar with local space.

Raydekk
2011-Apr-18, 07:32 PM
Great thread Sampanviking, I'm also fascinated by this subject. That's why I started working on the 3D Galaxy Map 2 years ago.



This of course only works because we are looking at a two dimensional representation of a three dimensional space and doing so from a fixed perspective. Any galactic map in the modern media is going to be three dimensional and with unlimited perspectives.

This means that a map has to be user friendly and Galactic Maps are going to be no exception. As human beings we love shapes and relate to them very easily. A map of the earth is instantly recognised at a high scale on account of the shape of the continents and even young children quickly can become good at recognising bits of Continental shape and relating them to the overall picture.


Agreed, the Galaxy map has to be 3D. While an Earth map can easily be understood in 2D, using colors to define its depth (mountains, plains, water), a 2D Galaxy Map is hard to comprehend.

Take http://upload.wikimedia.org/wikipedia/commons/8/89/236084main_MilkyWay-full-annotated.jpg for example. You have a nice view of the galaxy's shape, and you can distinguish the main features of the galaxy. But you cannot map all the stars in the galaxy like this. You won't be able to see the stars' depth. At best you can distinguish nebulae, gas bubbles, molecular clouds.



Well the same principle must surely apply to the Galaxy and at the highest resolution it does. Fortunately the galaxy is an discreet object with noticeable structure, which is just what we as a species like. It’s a memorable shape, easily recognisable and not to difficult to differentiate from other Spirals (in representation), once you take the trouble to study it.

When we look at a map of the Earth we see not only shapes but also Geography and we give this Geography names, usually starting at a Continental level and then zooming in to nation states, provinces, counties, Cities etc etc, not to mention natural features of the landscape such as Mountains, Rivers and Hills. This naming process means that not only can we recognise shapes of Geography, we can also describe them succinctly and precisely. If we like shapes we love names and putting the two together is our most powerful navigational tool.

This means that we must consider issues of scale and appreciate that detail must mean different things at different levels of resolution. It also means that we must become better at defining the Geography of the local Galaxy and more used to using it.


That's one of the first things I thought before working on the map. What is the best way to visualize the Milky Way Galaxy? Start from outside the galaxy, where you have all the major structures (the core, arms) and then take the user when the Solar System is. Before reaching the Solar System, show the user some of the nearby stars with a few characteristics like size(compared to the Sun) and spectrum. Having over 100.000 mapped stars from the HIP catalogue, showing them all at once would have been quite a visual mess. So splitting them in 10-parsec cubes seemed like a great idea, this way the most populated sector had around 80 stars. Even so, something was missing. Having the galaxy split into 10-parsec cubes resulted in a depth of around 370 cubes, still hard to comprehend where exactly our stellar neighbourhood was located. Including another layer of information in between these two scenes like inner arm structures (bubbles, molecular clouds) was the solution.



The basis of this geography would be to define regions of space by their distance from the sun using a set of concentric spheres, probably at about 10 parsec intervals and each layer given a specific name. Into these spheres I would overlay the natural structure of the galaxy and use it to determine discreet regions which again would be specifically named.

These simple actions reproduce in the Space around us, a Geography which is the equivalent of terrestrial continents and countries. It has visible and identifiable shape and it is named, which are the very factors which we recognise and respond to best.

It also does something else, it starts to promote the notion that we are not just an Island Solar System but part of a local group of stars which themselves relate to other nearby groups. This is important, as it is this that gives the geography context and meaning.

Once the rings and regions have been defined it will be possible to subdivide the larger areas into sections – the States or Provinces of Space and these too should be named to give them a sense of individual identity. Needless to say the name of the brightest star within any individual section, should be a prime candidate.

Finally within the sector there are the individual stars themselves – the cities of Space, which can then be presented with all the required or available level of detail.


While exploring the sectors it is very easy to get lost. While in the 10-parsec sector view, some additional structural information is necessary. First, I was thinking of giving the user the possibility to see adjacent sectors, but darkened(or blurred, to show that these specific stars are not part of the current sector), and a clear delimiter of the sector. Second, having the possibility to observe the "supersector" (for example if we are viewing sector(x,y,z)=(0,0,0), we zoom out and now the supersector contains every sector from (-1,-1,-1) to (1,1,1)). Not every star is shown in the supersector, everything below a certain size is hidden. Third, showing faint inner arm structures (bubbles, molecular clouds, nebulae, etc); this way while exploring the sectors you still know where is the current sector located in relation to the inner arm structures.

This is not doable in a web application (like 3DGalaxymap) - maybe only the supersector and the darkened adjacent sectors, but it is doable in a desktop application (like Celestia).



I would be pleased to hear comments and suggestions on these matters and would also be interested in any other websites you know which have tried to solve the mapping problem.


A few more things to take into consideration:

1. Web applications are very limited compared to desktop applications. Only a certain amount of polygons can be displayed on the screen in a web application. At best I'd say 2000 stars at once, but the framarate would probably be unbearable. That's why I had to split the map into different scenes.

2. Both web and desktop applications require a database. The database structure must be well thought, for example when migrating from the HIP database(100.000 stars) to the GAIA mission database(future mission - aim to map 1 billion stars) - the time to retrieve all the stars from the Solar System sector from 100k stars should be similar to the time to retrieve all the stars from the Solar System sector from 1 billion stars. There should be no significant degradation.

3. Even with 1 billion stars mapped, the galaxy's structure won't be distinguished. There is a middle way solution here. Generate a galaxy with dummy stars resembling the NASA artist's concept. Remove all the dummy stars from the sectors that have actual mapped stars(and some adjacent sectors as well). Give the user the possibility to see only the mapped stars, and compare that image to a generated artist's concept view of the galaxy.

4. It is imperative not to let the user to get lost in the application. Show markers, structures, something to help him/her understand the current position in space.

Raydekk

Sampanviking
2011-Apr-19, 09:53 AM
Thank you all for your responses and you have generated between you a lot of very valid points for discussion and as soon as work pressure relents for the Holidays, I will be very pleased to come back to them.

In the meantime however I must ask Raydekk, are you the creator and owner of the 3D Galaxy map site that I linked to in the OP?

Thanks

Raydekk
2011-Apr-19, 12:10 PM
Yes I am, you can check by sending me an email @ the address on the website (galaxy@3dgalaxymap.com)