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I am trying to represent trade flows on a world map where the size and direction of arrows indicate the exports/imports of a given country.

This type of map is commonly found in magazines and newspapers. However, I find it extremely difficult to make.

Is there any function in ArcGIS for Desktop or any free software that would help me in making it?

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I'm quite sure magazines use vector graphic editors (like Inkscape) to produce their images. –  underdark Jan 9 '11 at 15:18
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I love the idea, expressed by implication, that ArcGIS is free software! –  whuber Jan 10 '11 at 2:53

7 Answers 7

up vote 7 down vote accepted

This question (Representation of network flows) on network flows might be of interest.

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In December 2012, Esri has published a tool for generating flow maps. It is written in Python and available for ArcGIS Desktop users. And there is a ArcGIS Blogs post on generating flow maps with the links to the tool, some more information, and test data for the tool. I believe this is the kind of tool you would use to generate trade flows, too.

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+1 Thanks for this link. I've been looking for this for a while now. –  Aaron Apr 12 '13 at 19:03
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No problem. I believe this type of tools released by Esri should be somehow pooled to one place where it would be easy to browse them and search for. I miss ArcScripts :) –  Alex Tereshenkov Apr 12 '13 at 19:05

you can try the method that i used in ArcGIS: Create a line layer from a point layer and csv data file.

one question regarding the lines: you are representing the world and all the lines converge or diverge from a given country, right? brasil, as in your case, has trading relations with a bunch of countries and it will be difficult to distinguish all the arrows.

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I am trying to solve such trouble by having arrows of differing sizes representing different quantities. As the map will only focus on single product, I am sure it won't become too convoluted. –  relima Jan 9 '11 at 21:19

There seems to be multiple ways of looking at this. Either the lines are simple representations of numbers based on the records in points as graphics which would be good for one off maps, alternatively they are representations of value based on an attribute Value of a line. I would suggest creating a line Feature Class from all locations to all other locations, and then assign a separate unique ID for each line. Then you can create a join between your trade attribute Data and your linear feature data. The last stage is then to symbolise the lines based on the Quantities in your joined table. Then you can assign arrow size, directions and line information to each of the lines and customise.

Hope this helps, I am sure there are other ways as well, CDB

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Clearly a bit delayed, but this question: How to make radial flow map showing curved lines over short distances links to a great article by Esri called Creating radial flow maps with ArcGIS that will help answer your question.

Using the techniques described in the article, you can use the XY to Line tool in order to create your curved map. I put together a very custom ModelBuilder tool (custom to my needs) that would create the O-D table, populate the XY values of the source points, and then use the XY to Line tool to generate the Arcs. It involved a lot of "Add Field", "Add Join", "Point Distance", and "Calculate Field" functions, but it turned out very well, aside from arcs crossing the 180 degree line. Next step would be to try to force the arcs to stay "in frame" only (for example, from North America to Asia, crossing over the Atlantic instead of the shorter distance over the Pacific).

Flow map from ArcGIS

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I realize this post is old but I'm sure many others have the same question, most likely in creating a simple flow map for a school project or paper. If you are looking for a simple trade flow map you might be surprised by the ease and effectiveness of using powerpoint. It's much easier to create really nice arched arrows in powerpoint than it is in Illustrator and certainly easier than in ArcMap. Obviously if you are looking for something more in depth and the actual widths of the arrows needs to accurately represent your export numbers than this would not be your best option.

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