Finding Trade Routes?

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Assuming I have a resource that I can't trade internally, is there any way to find out what other nations I might be able to trade it with, aside from one by one openning the diplomacy window?

Edit: Also, I find that sometimes, I can trade over sea, and other times not at all... do I need a navy stationed to allow trading, or is there another trick?

And, I know that certain improvements can increase the distance that you can trade from, but is there any way to know what distance you can trade from, without trying to trade with each province nearby? Is there a formula to this?

Thanks in advance for helping me with these important geostrategic questions.

Man, I love this game. I love the fact that I am fighting for every inch of my empire, always. Rome: Total War was a great game, but it was too easy to steamroll your enemy and capture all their territory at once. In this game, I feel like you have to make a much more sober assessment about going to war, and what you can get out of it. Epic!

 

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If you click on the trade map, it shows you what trade routes are active for all nations/empires.

Sometimes I can't trade between two provinces, but it's not always clear to me why that is.

 

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Coastal provinces can trade with any other coastal province and any contiguous inland provinces.

Inland provinces can only trade with contiguous provinces.

A province may not trade for the same good with more than one other province. e.g., If Roma is getting wheat from Samnium, it cannot also get wheat from Apulia.

I suspect that road networks are going to allow trade with noncontiguous provinces, but I don't know exactly how because my people haven't discovered roads yet.

 

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A stone province cannot trade with another stone province. A province receiving stone cannot receive from another stone province. A coastal province can trade with any other coastal province. Landlocked provinces can only trade with neighbor provinces (unless a road network is connected between the target and destination).

From what I've experienced, it's best to fill as many trade slots as possible in your landlocked provinces before you begin with the coastal provinces. Maximizing the number of trade routes is more important than maximizing quality, of course there are other reasons too (like gaining population and civ value, etc.)

 

[unmerged(102510)]

For coastal routes, sometimes when I try to negotiate trade with an AI faction, I see "no trade route available" -- does just mean that the province I would be trading with is inland somewhere else?

Also, is it just me, or do I tend to earn a lot more money for foreign trade routes. Wouldn't it make sense to maximize these, assuming I did not need the related bonus? (E,G, greece has a lot of Iron, why not try to trade the coastal iron to someone far away?)

One more thought -- the inland rule you mention -- I guess that makes requesting trade access pointless until you have roads, correct?