### 2D Grids

Certain series (i.e. Color Grid, Contour, Surface, Triangle Surface, Tower, Water Fall, and 3D Points) with three series components - Position, Depth,  and Value - require that the data in the Position and Depth components form a special two-dimensional grid, or 2D grid. For these series, the 2D grid must be built on the xz plane of the graph with the x values and z values associated with the Position and Depth series components, respectively.

The easiest way to setup a 2D grid is to use the Setup 2D Grid sub menu on the Data menu (which is also the context menu of the active data table or data sequence). This sub menu contains two menu commands: Rectangular Grid and Circular Grid. Selecting either one opens the 2D Rectangular/Circular Grid dialog box with which the corresponding 2D grid can be set up on the active data table or the current data table of the active data sequence.

Selecting the Rectangular Grid menu command sets ups a 2D rectangular grid on two data-table columns: one is used to contain the x values (the data in the Position series component) and is called the X grid; the other is used to contain the z values (the data in the Depth series component) and is called the Z gird. Both grids are equally spaced. The start, end, and step values of each grid can be customized with the 2D Rectangular/Circular Grid dialog box. Color Grid, Contour, Surface, Tower, Water Fall, and 3D Points use 2D rectangular grids.

Selecting the Circular Grid menu command sets ups a 2D circular grid on two data-table columns. In a 2D circular grid, the grid points are equally spaced in the two dimensions of the polar coordinate system: the radial dimension (denoted as r) and the angular dimension (denoted as q). The start, end, and step values of the grid points in these two dimensions can be customized with the 2D Rectangular/Circular Grid dialog box with the limitation that the start and end values of the angular dimension are fixed to 0 and 2p (360°), respectively. The polar coordinates of the grid points are then transformed into coordinates in the xz plane using the following formulas:

x = rcosq                                    (1)

z = rsinq                                     (2)

It is obvious that the grid points generated this way locate on a set of equally spaced  concentric circles about the origin of the xz plane. Triangle Surface uses 2D circular grid.