RockWorks | Utilities | Grid |
Trend-Surface Analysis | Report
Use this program to determine regional trend for selected data in the main data sheet. This can help you to determine what trend order to select when creating a Trend Surface grid model, and it can help you to isolate regional anomalies by computing trend residuals. These tools are offered:
- Use the Trend Surface Analysis | Report command to perform a trend surface analysis on a selected Z-value column in the data sheet and to list the correlation and residuals for first through sixth order polynomials in a report. The completed report is loaded into a RockWare text window. You may save the report text to disk, print the report, or copy its contents to the Clipboard for pasting into other applications.
- Use the Trend Surface Analysis | Residuals command to perform a trend surface analysis on a selected z-value column and compute the residuals for a selected polynomial order, representing the difference between observed z-values and trend z-values. The residuals are stored in a data sheet column of the user’s choice. See Computing Trend Surface Residuals for details.
Menu Options
- Input Columns: Select the input data in the left pane of the window.
- X (Easting), Y (Northing): Select the columns in the data file that contain the X and Y coordinates for the sample sites.
- Z (elevation): Select the column that contains the data to be analyzed.
Step-by-Step Summary
- Access the RockWorks Utilities program tab.
- Enter/import your data into the datasheet. This tool requires that you have a data set displayed in the Utilities data sheet, containing multiple sample sites with X and Y coordinates and a Z value of some kind for which the trend surface will be computed.
- Select the Grid | Trend Surface Analysis | Report menu option.
- Enter the requested input settings, as described above.
- Click the Process button to continue.
The program will compute first through sixth order polynomials for the selected data, and display the completed report within a text tab in the Options window. Click here to see a sample report.
The report can be used to determine how well any of the trend surface models fit your data. The higher the correlation coefficient, the better the fit. This information can be helpful in determining whether there is much regional trend to your data. By isolating regional behavior, local anomalies can stand out.
This report can also be helpful if you are creating a trend surface map of your data, by providing correlation information. See Trend Surface Gridding for information about creating trend surface maps, and examples of different polynomials.
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