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FAQ: Why can't point data be linked to the point parameters of the Create Fishnet tool in Model Builder?

Question

Why can't point data be linked to the point parameters of the Create Fishnet tool in Model Builder?

Answer

There are three point parameters to the Create Fishnet tool:

  1. Origin coordinate
  2. Y-axis coordinate
  3. Opposite corner coordinate (optional)
In the tool dialog, these coordinate parameters are expressed as separate X and Y values. It is possible to enter values for these parameters manually in the tool dialog, but it is not possible to link a data item of point data type to the parameters in Model Builder. The model user interface allows links from point data items to be connected to the tool, but when the tool is opened, the link may not be honored.

The reason is that these parameters have been customized in the underlying code for the tool, and no data types are recognized for linking.

If a Template Extent data type is linked to the tool, the Origin and Y-axis coordinates are automatically populated from the extent values. The Y-axis coordinate then lies along the Y-axis of the extent range. It is not possible in Model Builder to assign a Y-axis coordinate not along the Y-axis of the extents, and there is no similar workaround for the Opposite Corner coordinate.

It is possible to specify these coordinates by calling the tool in Python. The data type accepted by the tool for point coordinate values is not a point data type, but rather a string consisting of <X coordinate value> <space> <Y coordinate value>. In this way, a Y-axis coordinate not along the extent boundaries can be entered. The same format applies to the Opposite corner coordinate, if supplied.

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