The x-y-z Axis System
For finite-difference models (MODFLOW-2000,
MODFLOW-2000 GWT, MODFLOW-96, MOC3D, and MT3DMS), the x-y-z axis system is not
explicitly defined by the models. Model Viewer defines the axes as follows:
- The positive x axis is oriented along a row of cells and points in the direction of increasing
column numbers, as defined in MODFLOW. (See figure below.)
- The positive y axis is oriented along a column of cells and points in the direction of decreasing
row numbers, as defined in MODFLOW. (See figure below.)
- The positive z axis points vertically upward.

For the finite-element model SUTRA, Model Viewer uses
the same the x, y, and z axis system as that defined in the input data.
- For ease of spatial reference and orientation,
Model Viewer normalizes the x, y, and z coordinates with respect to the bounding box. (Normalized coordinates are used to specify the positions of
cropping planes and the axes symbol.)
- The bounding box is the smallest box that contains all active cells.
The edges of the bounding box are aligned with the x-y-z axis system.
- The x, y, and z coordinates take on 0 or 1 at the
corners of the bounding box, as shown below.
