Flow maps room a type of object map provided in cartography to show the movement of objects between different areas. These types of maps can display things prefer the activity of goods throughout space, the number of animal species in a details migration pattern, as well as traffic volume and stream flow. They can likewise show both qualitative and quantitative data. Circulation maps usually represent the motion of goods, weather phenomena, people and also other living things with line symbols of various widths. Thus, the use of currently on a flow map is similar to the usage of graduated symbols on other types of thematic maps (Chang, 2012).

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When appropriately designed, flow maps space beneficial due to the fact that they allow cartographers, GIS analysts and map users alike to easily see the distinctions in magnitude of a wide range of item across room with very small map clutter (Phan, et al). This in turn allows businesses to watch where the bulk of their assets are going, commuters come see web traffic patterns, and meteorologists to check out wind patterns.

This write-up provides a straightforward overview of circulation maps and a description of just how they work. It additionally describes the three different varieties of circulation maps and also explains the characteristics and also components that a great flow map. Lastly it presents several examples of different species of flow maps.

How circulation Maps Work

Flow maps typically use present to present the activity of people and also goods between various locations. The lines are varied in broad to represent the amount of flow (Sathyaprasad). Thus if there is a an extremely wide line reflecting traffic top top one California roadway and also a really thin line reflecting traffic ~ above another, the road with the more comprehensive line is typically the one that contains an ext traffic.

Because the activity of goods and also people space usually shown lines, most circulation maps are produced with vector, instead of raster, based data so that they can display movement consistently over the Earth’s surface (Buckley). In vector based flow maps, the vectors room points or present that organize information around the direction and magnitude that item the is moving (Buckley). The points and lines have the right to then it is in overlaid onto a map to show the movement throughout a provided area.

Vectors have the right to be symbolized in a flow map with various orientations, point size, and also line size or broad to display direction and magnitude. For example, circulation maps showing an international wind patterns regularly have lines through arrows ~ above them. The point of the arrow shows the direction of motion (straight, circular, curved, etc.), when the width of the line shows the wind’s intensity.

Although most circulation maps use vector data, ArcGIS has actually recently introduced a device for distributive circulation maps (discussed in the following section) that uses raster data. The Distributive flow Lines device (DFLT) is a spatial analyst device in ArcGIS that generates distributive flow lines native one source to countless different location points. The DFLT is completely raster based until the finish when it creates a vector based circulation line feature class to be provided on circulation maps (Bgerit). Part ArcGIS individuals say this raster based tool is optimal because it enables for an ext control end the circulation lines and also it decreases processing time (Bgerit).

Another vital thing come note about flow maps is that they can use and display both qualitative and quantitative data. Because that qualitative data the maps usually display screen symbols of uniform width the just show movement with arrows (McGraw-Hill). This data is a connection of some sort and also it is not based on magnitude. Quantitative circulation mapping supplies lines and symbols of different widths and sizes come show alters in magnitude between areas.

Types of circulation Maps

When feather at and creating circulation maps the is important to keep in mind that there room three an easy categories for the maps. These room radial, network and also distributive. Radial flow maps present relationships in between one resource and countless destinations and use different lines radiating the end from a starting point to show movement. Network circulation maps present the quantity of flow over an existing network (Sathyaprasad). These species of flow maps most typically show transportation and communication networks. Distributive circulation maps room maps that show relationships between a solitary source and also many destinations choose a radial circulation map. These maps are different however, since they frequently have a large, single line created from one source and the forks into many smaller lines when they reach your destination.


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Charles Joseph Minard created this circulation map the French alcohol exports because that 1864. Source: Mediawiki Commons, publicly domain.

In addition to these three map categories, flow maps can likewise be still or animated. The classic printed wind, traffic and other maps showing the activity of products across an are are still yet computers now enable interactive, animated circulation maps that can show things like wind rate during and after a hurricane for instance (Buckley).


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Dynamic Wind Map by Fernanda Viégas and Martin Wattenberg that the site Hint.FM

What makes a great Flow Map?

Whether radial, network or distributive all great flow maps should have actually the complying with characteristics and also components as explained by Doantam Phan et al. In their paper, “Flow Map Layout”:

Intelligent Distortion: Some flow maps attribute distortion to show the movement of goods. As such it is vital that any intended distortion not readjust the definition of the map.Merging of Edges that Share Destinations: If over there are numerous lines going to the same location it is crucial that your edges be an unified to mitigate map clutter.Intelligent edge Routing: In some instances branches or lines on flow maps will route themselves through the center of the map. This deserve to obscure the various other lines so they have the right to be routed come the sheet of the map for this reason that every one of the data can be conveniently seen.Layering and also Branching Structure: Some flow maps have actually a common set of nodes. In these situations layering of their lines functions well to alleviate map clutter.Linear or Logarithmic screen Widths: circulation maps deserve to use both linear and also logarithmic display widths. The is vital to choose the correct one to best show the data.

Example of circulation Mapping

Because circulation maps can use a wide variety of data over there are additionally many different projects in a plethora of fields that deserve to use this mapping technique. Business geographers deserve to for example, use circulation mapping to examine the amount of charcoal exports from a details country. Hydrologists have the right to monitor stream circulation for a specific state or region. City planners and transportation geographers can use flow mapping to research traffic patterns and the volume of cars on certain roadways to identify the best places for brand-new businesses and/or residential developments.

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Map of voting cardinals showing where they arrived to the Vatican from. Map: Caitlin Dempsey

To learn an ext about circulation maps and also to exercise making them with a selection exercises because that ArcGIS, visit the ArcGIS – flow Mapspage ~ above ArcGIS.com.

References

ArcGIS. (n.d.). ArcGIS – circulation Maps. Re-cover from: http://www.arcgis.com/home/group.html?id=62918569d92344efa8b50bf3df5e8f25 (21 march 2014).

Buckley, Aileen. (April 2013). “Go through the Flow.” ArcWatch: GIS News, Views and also Insights. Retrieved from: http://www.esri.com/esri-news/arcwatch/0413/go-with-the-flow (21 march 2014).

Chang, Kang-tsung. (2012). Introduction to geographical Information Systems. McGraw-Hill: brand-new York, sixth Edition.

McGraw-Hill. (n.d.). Mapping practice – thematic Mapper: The circulation Map. Retrieved from: http://highered.mcgraw-hill.com/sites/dl/free/0072943823/599982/Flow_Mapping.pdf (21 march 2014).

Phan, Doantam, Ling Xiao, Ron Yeh, pat Hanrahan, and also Terry Winograd. (n.d.). “Flow Map Layout.” Stanford University. Retrieved from: http://graphics.stanford.edu/papers/flow_map_layout/flow_map_layout.pdf (21 in march 2014).

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Wikipedia.org. (6 November 2013). Flow Map – Wikipedia, the free Encyclopedia. Re-cover from: http://en.wikipedia.org/wiki/Flow_map (21 march 2014).