Visualizing Streams WITH TAPERED LINES

CARTOGRAPHY Henri Saijos, Jul 21st, 2014

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Modern cartography is usually based on somewhat static and structured digital GIS data. With contemporar techniques, to achieve a cartographically acceptable result with stream tapering and splined stream labels would need a lot of time and work. In this article we are presenting an easy way to visualize a simple stream network using a tapering technique and editable label elements provided by Mapnor Cartographer ArcGIS Extension.

Tapering Streams

Tapering streams is a common cartographic technique to visualize a natural river network and the direction of water flow. The general idea is use gradually decreased line width to mimic that in general streams tends to get shallower when moving to headwaters. In simpliest way tapering can be done using a line network with flow attribute and graduated line width renderer. Anyhow, tapering inside a single feature is enabling even more realistic result. This can be achieved easily by using a Mapnor Cartographer and Tapered Lines drawing type. Combined this with static river and stream classes, a cartographer can easily create a realistic branching network that tapers from a tricle at the headwaters and expands to a torrent at the outlet.

To create a stream network, first thing is to classify data to applicable classes. In our example we are using only two classes. One with a static width symbol to a major rivers and the other for a tapered minors. After classifying data and setting a simple line symbol and width, we change the minor class style to a Tapered Lines style.

Classifying data and setting styles.

With Tapered Lines class there is only couple of parameters needs to be considered: Tapering steps and a line width range. The base line width specifies a starting point line width, which normally is a bit smaller or same than a connected major river width. This width is then gradually decreased using a specified steps value until the minimal width value is reached. The step lengths are calculated individually for each stream to achieve a natural and realistic result.


Minor river changed to a tapered style

Note that tapering direction depends on the line digitizing order. In a case that lines are digitized agaist the stream flow direction this direction can be reversed by default.

Labeling Streams

To label streams we can use standard annotation functionality. Anyway, in this example we are using a new element type provided by Mapnor Cartographer: Spline Label. Like all cartographic elements it is always tied to a feature and cannot exist without the host. With this element it is important to specify a default values in optimal way to minimize a need for an overrides. With spline label, generalize and smooth properties are essential to achieve a decent and smooth labels. Default location within each line can be set to a static location within a line or location can be automatically opmimized using an various parameters. The default location, can be of course overridden, by setting the element to editable.


River name spline label in default and optimized location.

Result

Using some helper parametes like visibility expression we can easily limit the map label count and not label shorter lines. When all defaults set and after a short cartographic editing session with drag and drop labels to their optimal locations, we have created a realistic river branching network. Tapered streams with splined name labels all within a single layer, which can be easily saved to a layer file or copied to another map as a default.

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