Question: What does distance mean in NetLogo ?

[vidus...@gmail.com]

Hi All 

I have a confusion about distance in NetLogo. 

In my understanding, NetlLogo distance calculates distance between the patch centre of start patch to the centre of destination patch. So when agent moves, the distance is one patch distance (please correct me if I have misunderstood this).

In my model, environment is created by importing 3km * 3km forage availability raster using GIS extension. Based on the patches forage value agent selects and then move to a suitable patch and updates distance travelled by taking sum of distance travelled every time step. 

My question is - If the world is resized to match the raster extent, is this distance a distance in km ? If not, how to convert that ? 

Thank you

Kind Regards

Vidushi   

[Wade Schuette]

I suspect that Netlogo reported distances are always in Netlogo coordinates, so a distance of 1 is 1 patch.

I suspect you can compute the exact relationship for a small region of the Earth ( flat earth approximation ) from looking at

the ratios in

gis:set-transformation gis-envelope netlogo-envelope

Regardless I'd double check my work by finding two points in your map that you know the kilometer distance

between and seeing if your multiplicative factor times the NetLogo reported distance is the same number.

Or conversely, figure out the factor by using the ratio of the distance in real world between those two points

and the distance reported in NetLogo between them.

Of course, if the section of the world you are mapping is large enough that curvature of the earth matters,

so you're into spherical geometry you'd have to figure out the latitude and longitude of each point and

some subroutine that computes the great-circle distance between those two points.

Wade

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[Michael Tamillow]

Both turtles and patches inherit from "agents". The description for distance is:

distance agent 

Reports the distance from this agent to the given turtle or patch.

The distance to or from a patch is measured from the center of the patch. Turtles and patches use the wrapped distance (around the edges of the world) if wrapping is allowed by the topology and the wrapped distance is shorter.

ask turtles [ show max-one-of turtles [distance myself] ]
;; each turtle prints the turtle farthest from itself

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[Vidushi Patel]

Thank you All that helped clarify my confusion. 

Thank you for the suggestion Wade. I will check with the known points to make sure I am using the right distance. 

Kind Regards

Vidushi

Vidushi