# Calculating the Z Value of the Surface at a Point

The Grids | Calculate | Point
Sample command samples Z values from a grid at any point. To perform
the operation, create a data file with X and Y coordinates for the points
you'd like to sample and click the Grids
| Calculate | Point Sample command.

## Example

Consider a grid file that ranges from zero to 10 in the X and Y dimensions,
and you want to determine the value of the surface at the points (1,3)
and (4,2) on the surface.

Open a new worksheet window with File
| New | Worksheet.

In column A, type the X coordinates for the
points you wish to find the Z value, e.g. type 1 in Row 1 and 4 in
Row 2. In column B, type in the Y coordinate, e.g. type 3 in Row 1
and 2 in Row 2. Add as many points as you want into the data file
by entering the coordinates for each point into a different row in
the data file.

Use the File
| Save As command and enter a name for the data file, for example
PointSample.dat. Click Save
and the XYZ data file is created.

Click the Point
Sample command.

Specify the Input
Grid, XY Data, and
Data Columns in the Point Sample dialog.

Click OK
and a worksheet is opened with the Z values from the points you entered.

See Also

Calculating
the Agreement between a Grid and the Original Data File

Grid
Residual