CODEWITHSUNDEEP
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Switters
Switters

Reputation: 119

Calculating distance and determining units of measure in Netlogo using GIS extension

I'm using GIS extension in Netlogo to import shapefiles, then creating turtles from attributes of the shapefile. I'm using the distance primitive to calculate the distance between turtles. I know Netlogo does converts the shapefile to netlogo space, so the distances wouldn't be reported the same b/w GIS and Netlogo. For example, in GIS distance between turtle A and B is 49550 meters. In Netlogo, it's 0.2038. Is there a way to determine what the units of measure are in Netlogo? Is the conversion always the same or does it depend on the projection? Thanks for any assistance.

Upvotes: 1

Views: 378

Answers (2)

JenB
JenB

Reputation: 17678

The distance in a NetLogo model is entirely arbitrary. You are deciding the unit of distance implicitly when you import a GIS real-world structure into whatever number of patches there are in the NetLogo world. In your case, the easiest way to work out the conversion factor is likely to be to find a few points on your GIS and get their xcor and ycor. From your question, haven't you already done this? You have said that 0.2038 is 49550m.

There will also be problems coming out of the projection - if your model covers a large real world area, then the mismatch between the surface of a sphere and a flat model will mean the distance conversion is different at different locations.

Upvotes: 3

Hannah H.
Hannah H.

Reputation: 276

Maybe this helps. I found a model here, which is also trying to work with space.

I quote: "Grid cell size does not represent an absolute spatial unit (e.g. meters); instead, the size of grid cells is only meaningful with respect to the step size of individuals which can vary with user input."

Upvotes: 1

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