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NetLogo Models Library:
Code Examples/Extensions Examples/gis

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GIS Gradient Example

Note: If you download the NetLogo application, every model in the Models Library is included.

WHAT IS IT?

This model was built to test and demonstrate the functionality of the GIS NetLogo extension. It simulates raindrops flowing downhill over the Earth's surface.

HOW IT WORKS

This model loads a raster file of surface elevation for a small area near Cincinnati, Ohio. It uses a combination of the gis:convolve primitive and simple NetLogo code to compute the slope (vertical angle) and aspect (horizontal angle) of the earth surface using the surface elevation data. Then it simulates raindrops flowing downhill over that surface by having turtles constantly reorient themselves in the direction of the aspect while moving forward at a constant rate.

HOW TO USE IT

Press the setup button, then press the go button. You may press any of the "display-..." buttons at any time; they don't affect the functioning of the model.

EXTENDING THE MODEL

It could be interesting to extend the model so that the "raindrop" turtles flow more quickly over steeper terrain. You could also add land cover information, and adjust the speed with which the turtles flow based on the land cover.

RELATED MODELS

The other GIS code example, GIS General Examples, provides a greater variety of examples of how to use the GIS extension.

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