What exactly do the parameters of fishnet mean?

AmandaHalperin

I'm doing some coding in Python with ArcPy with fishnets, and I'm trying to understand more about the tool.

Specifically, the documentation refers to: 

origin_coord	The starting pivot point of the fishnet.	Point
y_axis_coord	The Y-axis coordinate is used to orient the fishnet. The fishnet is rotated by the same angle as defined by the line connecting the origin and the y-axis coordinate.	Point

I'm having trouble understanding, visually, what the origin coordinate is and what the y_axis_coord is. How does this work?

Secondly, I'd like to be able to specify the extent of the fishnet using latitude and longitude, which is an option (I think):

template (Optional)

Specify the extent of the fishnet. The extent can be entered by specifying the coordinates or using a template dataset. Left—XMin value Right—XMax value Bottom—YMin value Top—YMax value

Extent

How does this option interact with the required parameters of origin_coord and y_axis_coord?

DavidPike

origin_coord is the bottom left corner of your intended output fishnet grid.

y_axis_coord is used to orient the fishnet output.  If you want a 'normal' rectangular fishnet you would just take the same x value of the origin_coord and add 1 unit of measure to the y value of the same origin_coord.

you would set a geographic coordinate system output for the fishnet as an environment setting:

env.outputCoordinateSystem = arcpy.SpatialReference([WKID])

and doing the same with the y_axis_coord as per a planimetric CRS you would have the grid formed of lines of lat long, seen as 'rectangular' in the plate carree/equirectangular proj.

Not used it myself but I think the extent would set the maximum bounding extent of the output if the corner_coord is not specified.