Contouring overview

The first step in extracting contours from your data is to interpolate the data onto a grid.

You can use the Contouring area submenu to create a grid mesh area for your data.

To set up the parameters for a new grid you can either use the PARAMETERS Layer Defaults function to set default values for the grid mesh parameters based on the spread of the data in a defined graphics layer, or you can directly enter the parameters using the PARAMETERS Edit Mesh function. The first approach is quick and easy, the second approach gives you more control.

If you chose to use the second approach, the recommended way to set up the parameters for a new grid is as follows:

(i) Use the 2D Grid function to overlay a 'graphics grid' on the initial data. Use this to visually estimate candidate values for the Grid Model origin and extents etc;

(ii) Use the PARAMETERS Edit Mesh function, and fill in the ENTER GRID MESH PARAMETERS form with the candidate values;

(iii) Applying the ENTER GRID MESH PARAMETERS form will display the grid coverage on the screen. The grid coverage is represented by 4 points showing the 4 corners of the grid mesh you have defined. These 4 points are stored in a closed clockwise segment in the graphics layer grid_coverage, and this layer can be saved to a string file. You may wish to type ZOOM ALL to get a better view of your data and grid coverage;

(iv) You will find that with some fine tuning with the PARAMETERS Edit Mesh function you will be able to easily create a grid with exactly the coverage you require BEFORE you commence any potentially lengthy interpolation or contouring calculations. You can also use the COVERAGE Create View and COVERAGE Delete View buttons to toggle on and off the view of the grid coverage;

(v) Only when you have visually confirmed that you have a grid you are happy with, do you then press the Process Grid function to begin interpolating into the grid and extracting contours.