Is this a viable world river system?

[Porklet]

I have tried to create a realistic river system for the world I am working on based on the information I got from the Sticky post "How to get you rivers in the right place" by Ryan K. I think I have done that, but I wondered if some more experienced map makers might take a look at my work. The map is 6,000 miles by 6,000 miles and is representative, at this point. The rivers shown are major river systems. I have included the 30th parallel in order to show the dry/arid zones and the wet zones to the north.

The area marked "A" is an experiment. I don't know if it can function this way. The south side of the mountain chain is in a rain shadow. The rivers flowing out of it are from the substantial snow melt cascading out of the valleys south. There are a few elevated mountain lakes, and the system then flows in to an expansive and very dry savannah. I intended for the map to show a varying flow river system collecting in a dry lake bed, filling, and evaporating seasonally (much like the African savannah without the torrential storms). I am wondering if that situation is realistic, and, if so, is it clear on as presented on the map?

Thanks for any help.

[Hai-Etlik]

That river looks fine. There are plenty of 'endorheic' lakes like the Caspian Sea, Great Salt Lake, etc, and there are also rivers that simply spread out into an inland flood plain and evaporate like the Okavango.

The long river in the northeast though seems to be following along a raised area of hills (though it's hard to interpret without contours) Those huge lakes up in the mountains without much of a catchment area feel a bit off too.

Overall, you've got the basic idea.

As a bonus bit of criticism, you've got a problem with your projection. You seem to be using a Equidistant Cylindrical projection (Parallels are all evenly spaced and vertical distances are all to scale.) However, that would produce severe distortion at the higher latitudes.

Take a look at the map of Earth here: http://en.wikipedia.org/wiki/Equirectangular_projection

See how the parallels (Horizontal grid lines) are evenly spaced, but horizontal distance gets stretched out more and more as you move away from the equator.

Along the N 60° parallel near the top of your map, distances are only half what they are at the equator (So the map is only 3000 miles wide at 60°). And at the very top, which appears to be about N 75°, it's just a little over one quarter the width at the equator, 1553 miles wide. Even at just N 30° the map is 5196 miles wide. There's no way to have a square 6000 miles on a side on the surface of a sphere 3820 miles in radius.

Unfortunately there's no easy solution or rule of thumb. All projections cause distortion. If you are most concerned with shape, don't care much about distance, and aren't worried about the poles, Mercator is your best bet. It stretches in BOTH directions as you move away from the equator which means things tend to stay the same shape.

My recommendation would be to move the N 60° line upward and call it a Mercator map. You'd be able to retain '6000 miles' along the equator, but away from the equator the scale would change.

You can get a graticule (Grid) for a Mercator map here: http://www.cartographersguild.com/sh...ector-Template

[Porklet]

That river looks fine. There are plenty of 'endorheic' lakes like the Caspian Sea, Great Salt Lake, etc, and there are also rivers that simply spread out into an inland flood plain and evaporate like the Okavango.

The long river in the northeast though seems to be following along a raised area of hills (though it's hard to interpret without contours) Those huge lakes up in the mountains without much of a catchment area feel a bit off too.

Overall, you've got the basic idea.

If the river you are referring to is to the right of the forest,then it's flowing between the raised hills and the raised elevation from the mountains to the east. I am not fond of that river. It was one of the first ones I attempted, and I had already considered removing it altogether or redesigning it.

Are you referring to the lakes in the hills north of site "A"?

[Porklet]

As a bonus bit of criticism, you've got a problem with your projection. You seem to be using a Equidistant Cylindrical projection (Parallels are all evenly spaced and vertical distances are all to scale.) However, that would produce severe distortion at the higher latitudes.

Take a look at the map of Earth here: http://en.wikipedia.org/wiki/Equirectangular_projection

See how the parallels (Horizontal grid lines) are evenly spaced, but horizontal distance gets stretched out more and more as you move away from the equator.

Along the N 60° parallel near the top of your map, distances are only half what they are at the equator (So the map is only 3000 miles wide at 60°). And at the very top, which appears to be about N 75°, it's just a little over one quarter the width at the equator, 1553 miles wide. Even at just N 30° the map is 5196 miles wide. There's no way to have a square 6000 miles on a side on the surface of a sphere 3820 miles in radius.

Unfortunately there's no easy solution or rule of thumb. All projections cause distortion. If you are most concerned with shape, don't care much about distance, and aren't worried about the poles, Mercator is your best bet. It stretches in BOTH directions as you move away from the equator which means things tend to stay the same shape.

My recommendation would be to move the N 60° line upward and call it a Mercator map. You'd be able to retain '6000 miles' along the equator, but away from the equator the scale would change.

You can get a graticule (Grid) for a Mercator map here: http://www.cartographersguild.com/sh...ector-Template

That had not even occurred to me. This is my first map that wasn't drawn on graph paper. I have downloaded your svg file for use with GIMP. I have two days off so I will try to post something soon. Thanks for all of the help.

EDIT:
I have added my Mercator work thus far. Am I doing this right? I had to move it south in order for the equator to match my earlier works. The relative latitudes are going to change a lot about the world I thought I was building.

[Hai-Etlik]

EDIT:
I have added my Mercator work thus far. Am I doing this right? I had to move it south in order for the equator to match my earlier works. The relative latitudes are going to change a lot about the world I thought I was building.

I'd say you've got it quite a bit too small.

I would suggest you try to line up the equator with where you had the equator before, and the N 30° meridian (The second one up from the equator) with where you had it before. All the others will be different, but as those were apparently the ones you were focusing on, it makes sense to keep them same.

To simplify it, I've chopped out the part of the graticule you need to do that:

[waldronate]

Imm not sure that a Mercator projection would be a particularly good choice because of the rather extreme distortion heading northward. A simpler cylindrical projection might work, as might something like a Mollweide projection. I pulled out my elderly and creaky ReprojectImage program ( http://www.ridgenet.net/~jslayton/ReprojectImage.zip - although something like Hugin or any number of other image reprojection programs would also work here) and used a Mollweide projection on the basic image. Pulling back onto a sphere gives the last screenshot. If you have a flat map that you're starting from and aren't terribly worried about some distortion, then I really recommend picking a projection that will keep the latitudes at a slight expense of longitudes (unless it's absolutely critical that some points be exactly north or south of others).

As far as the river that you were asking about, two real-world examples are the Okavango delta in Africa ( http://en.wikipedia.org/wiki/Okavango_Delta ) and what was Tulare Lake in California's central valley ( http://en.wikipedia.org/wiki/Tulare_Lake ). Both had annual floods that spread out over many, many square miles and revert to grassland and/or marshes after that passes. Neither one has a whole lot of rainfall in the actual areas that flood, but collect rain from elsewhere.

[Hai-Etlik]

Imm not sure that a Mercator projection would be a particularly good choice because of the rather extreme distortion heading northward. A simpler cylindrical projection might work, as might something like a Mollweide projection.

Yes, Normal Mercator really isn't the best option for a continent map, but I suggested it as it's far and away the simplest option that can be implemented without needing additional software. If I were trying to map a continent this size and shape for general reference, I'd probably use a Chamberlain Trimetric projection but that's well beyond what I want to throw at a newbie.

[Porklet]

Yes, Normal Mercator really isn't the best option for a continent map, but I suggested it as it's far and away the simplest option that can be implemented without needing additional software. If I were trying to map a continent this size and shape for general reference, I'd probably use a Chamberlain Trimetric projection but that's well beyond what I want to throw at a newbie.

I have implemented your Mercator fix, see below. Do I understand this correctly? Every line north of the Equator is 15 degrees on the globe, or am I wrong? Thanks for the help.



Is there something I could do with the scale to make Mercator work better? I want the mechanics of the world to be believable, and I want environments in the tropics and near arctic without creating a massive world system. The idea was born years ago on notebook paper, portrait style. The map was only recently changed to fit in a square. What if I altered the scale to 6,000 x 3,000, or vice versa now that I think about it? Would that alleviate some of the distortion near the poles?

I am beginning to understand the use of the Reproject software by waldronate, but if I can use Mercator to establish the world system in its final form I want to go ahead and do that. Then I can play around with other aspects.

I saw an episode of "The West Wing" where C.J. had a meeting with the Cartographers for Social Equality. They maintained that the Mercator map was Euro-centrist and did not give adequate props to the southern hemisphere. They showed the Peterson (or Pederson or Pedersen) Projection and it freaked C.J. out. I thought they were exaggerating just to be funny, but apparently they weren't fooling around. I am beginning to understand why C.J. was freaking.

[Hai-Etlik]

I have implemented your Mercator fix, see below. Do I understand this correctly? Every line north of the Equator is 15 degrees on the globe, or am I wrong? Thanks for the help.

Yes, all the lines are at 15° increments, so the dark lines are 0° and the next line is 15° then 30° and so on.

Is there something I could do with the scale to make Mercator work better? I want the mechanics of the world to be believable, and I want environments in the tropics and near arctic without creating a massive world system. The idea was born years ago on notebook paper, portrait style. The map was only recently changed to fit in a square. What if I altered the scale to 6,000 x 3,000, or vice versa now that I think about it? Would that alleviate some of the distortion near the poles?

The "best" solution would probably be to make a rough world map, as in the WHOLE world with your continent where you want it. Then reproject it to a projection suitable for a map of JUST the continent like say, Lambert Conformal Conic, or Chamberlain Trimetric then refine it. Unfortunately, that would mean throwing out your existing map except as a reference.

As to the scale. For a map this size, there is no consistent scale. It's just not possible. Certain projections do manage consistency for particular cases. Equidistant Cylindrical has a consistent scale for measurements north-south and along the equator. Equidistant Azimuthal has a consistent scale for measurements from a single point. Covering a smaller area does help, but you want to cover the equator to the arctic which rather constrains you to being big. You could make the map less wide which would help. If the continent were shaped more like South America, for instance.

If you go with my Mercator option as is, you get equator to subarctic (A bit shy of 60°). I could adjust it to cover true arctic if you don't mind the 30° parallel moving down a bit.

With Waldonrate's Mollweide option, you do reach the arctic easily.

Another option is a conic like this Equidistant Conic:



Like your original map, it spans from S 15° to N 75° and preserves north-south distances. It also preserves east-west distances at N 15° and N 60° (the 'Standard Parallels' for this conic). As before the graticule is spaced at 15° intervals.

Unlike the previous options Waldronate and I have suggested, this is a projection specifically created for this continent.

I am beginning to understand the use of the Reproject software by waldronate, but if I can use Mercator to establish the world system in its final form I want to go ahead and do that. Then I can play around with other aspects.

I saw an episode of "The West Wing" where C.J. had a meeting with the Cartographers for Social Equality. They maintained that the Mercator map was Euro-centrist and did not give adequate props to the southern hemisphere. They showed the Peterson (or Pederson or Pedersen) Projection and it freaked C.J. out. I thought they were exaggerating just to be funny, but apparently they weren't fooling around. I am beginning to understand why C.J. was freaking.

The Equal Area Cylindrical projection (Aka. Gall-Peters which I think is what they are talking about) is a projection for the whole world that preserves areas, but massively distorts shapes and directions.

The equal area thing was a big issue for some a while back, but it's pretty much been dealt with. Mercator was initially designed for marine navigation by dead reckoning. A navigator needs to know which direction Greenland is, not how big it is relative to Africa. Equal Area projections are great if you need to know how big something is, but useless for anything else. Compromise projections like Robinson and Winkel Tripel ended up winning out as the projections of choice for world reference maps as they balance the various distortions out rather than trying to eliminate just one at the expense of the others. Mercator is making something of a comeback in web maps since it lets you easily "zoom in" while retaining shapes and directions.

[Porklet]

The "best" solution would probably be to make a rough world map, as in the WHOLE world with your continent where you want it. Then reproject it to a projection suitable for a map of JUST the continent like say, Lambert Conformal Conic, or Chamberlain Trimetric then refine it. Unfortunately, that would mean throwing out your existing map except as a reference.

As to the scale. For a map this size, there is no consistent scale. It's just not possible. Certain projections do manage consistency for particular cases. Equidistant Cylindrical has a consistent scale for measurements north-south and along the equator. Equidistant Azimuthal has a consistent scale for measurements from a single point. Covering a smaller area does help, but you want to cover the equator to the arctic which rather constrains you to being big. You could make the map less wide which would help. If the continent were shaped more like South America, for instance.

If I were to continue with this map as pictured below (with your new graphics thank you very much). Could I at a later date use it as a reference to then make it a part of a larger global map? I don't envision ever taking that step, but it would be nice to have that option. I had originally thought that the planet I would be working on would be half the dimensions of our earth. That would've made the 6,000 by 6,000 map roughly half of the planet. That seems like a bit much. I would prefer to leave the rest of the planet alone for now. I suppose the longitude shown on the image below would give me the relative percentage of the global map covered in my continental map.

I am satisfied with knowing the relative global positions of the locations on the map so that I can interpret things such as climate, relative temperatures, and celestial events such as the midnight sun. If I have to alter the scale at different latitudes that's okay with me. It's a work in progress.

Speaking of scale: What does happen to scale closer to the poles? I know the scale is reduced, but is it uniform based on the degrees from the equator? Is their an equation that can be used to convert distance from point to point? I assume scale at the equator is 1:1, or is the center point arbitrary? I have already noticed that some locales that were directly north of others are now far off to the east/west. It's unsettling, but north/south relationships are inconsequential.

I apologize if I am being dense. With the graphic that you gave me, along with waldronate's projections in a previous post, it's beginning to become clear. I should have made my world flat. Just kidding. I can see the map I have made as a spherical domain for the first time.

The only logistical issue I have is moving the island chain (area "A") so that its midpoint lies on the 65th parrallel (which I assume is north of the line just above it). Ugh, South America, huh?