Define extents for contouring
This function allows you to use the data in a defined graphics layer to set default values for the parameters that define your grid mesh. You will find this function very useful for quickly and easily producing a grid mesh which covers the spread of your data.
To run this function: Choose Surfaces > Contouring > Contouring area > Define extents, or...
First you enter the name of the graphics layer that contains your data. You then hit the Calculate button and the function calculates default values of the Y and X step sizes for the grid mesh based on the data in the graphics layer, and displays the values in the Y grid step size and X grid step size fields. If you prefer you can type your own values directly into these fields.
Layer containing data
In this field enter the name of the graphics layer containing the data that you wish to grid. The field browser gives you a pick list of the available graphics layers (the field default is the current working layer).
Y grid step size
Enter the Y (northing) step size for the grid mesh. You can get default values for the step sizes based on the data in the layer you have defined by hitting the Calculate button.
X grid step size
Enter the X (easting) step size for the grid mesh. You can get default values for the step sizes based on the data in the layer you have defined by hitting the Calculate button.
Selecting Apply in the ENTER DATA/MESH OPTIONS form displays the ENTER GRID MESH PARAMETERS form. This form displays the grid mesh parameters as they have been set by the function. If you are happy with the default values simply select Apply in the ENTER GRID MESH PARAMETERS form, or you may edit the values if you wish.
Warnings
There are no points in the chosen data layer
The graphics layer you have defined contains no points, therefore default values cannot be calculated.
Grid step length must be above 0.001
You have violated the lower bound for the grid step lengths. Reenter a higher value.
Result
Once the function is completed the 4 points representing the 4 corners of the grid coverage are displayed in a closed clockwise segment on the screen in the graphics layer grid_coverage. You may wish to type ZOOM ALL to get a better view of the original data and the grid coverage.