Rating Tables are mathematically modelled relationships between depth and discharge for a water body. Using DataSight's analysis tools, you can easily test the applicability of a pre-existing rating table to measured Gauging data. DataSight’s Regression module can be used to generate a Confidence chart for the analysis and validation of rating equations. The regression analysis can be performed on the Gauging data, the Conversion Table data or both, and you can then adjust the modelled relationship and save it. An additional review of a ratings table can be undertaken in the Calculations Tool, by executing two data conversions and calculating the difference between the two tables.

Use the Regression tool

You require:

• A pre-existing rating table, known as a Conversion Table within DataSight. Refer to Create a Conversion Table.
• The Conversion Table must also be assigned to a specific site.
• Gauging Data for that site. Refer to Add Gauging Data.

1. Open Regressions.
2. Click Conversion Table to select the Conversion Table for analysis. You will be presented with a list of available Conversion Tables in the database.
3. Select the Conversion Table you wish to use for analysis and click OK. Within the Regression Tool, the Conversion Table area will be populated with data from the selected Conversion Table and the Regression Chart area will display the Conversion Table graphically.
4. Click Gaugings to select the Gaugings for analysis.
5. Select individual Gaugings by checking the boxes against their rows. This will populate the Gauging Panel of the Regressions Window, allowing regressions to be carried out on those selected, and plot the Gaugings graphically in the Regression Chart.
6. Select Criteria to define the upper and lower boundaries of the result set produced during analysis, along with the required number of increments required for the result set.
7. Once you have selected the Conversion Table and Gaugings you wish to use, click Analyse to begin regression analysis. A list of the available Regression Models will be displayed.
8. Select the applicable Model, or select All Models, or create your own Model using the in-built regression models.
9. Click OK. DataSight will complete the regression analysis and display the results of each model graphically. In the right panel, details of the Regression Models will be displayed. A graphical representation of the model will be displayed in the Regression Chart window in the middle of the Regression Tool. The chart legend is standard, displaying the six different series viewable in the Regression Models panel. Model details are displayed at the bottom of the Models window (at the right). This includes the R2 value, p-Value, Standard Error and Sum of Squares information. Further details can be found by clicking the Details button.
10. Click on the Confidence Chart This shows the rating table as the zero point and the Gaugings as a percentage off the curve. The quality of the Gaugings is also represented by scaled error bars - the larger the error bars, the lower the quality of the gauging measurement. The Confidence chart is interactive. When you hover the mouse over a gauging, details regarding the gauging are listed.
11. Return to the Regression Chart Once you have analysed the relationship between the rating table and your measured Gauging Data, you may wish to create a new Rating Table.
12. Scroll through the regression models from the Models tab on the right to identify the curve that lines up suitably with the existing data points.
13. Select the Analyse Results panel to display the results of the selected model.
14. Highlight the values you wish to move across to the Output Table, right-click and select Copy Selected Into Output. Data in the Output Table is displayed in the Chart area in blue.
15. The Output Table will be displayed in the charting area and can be saved (as a DataSight Conversion Table) by clicking the Save button on the toolbar and entering the Conversion Table Name, the X and Y axis Labels, and the Period of Applicability. You can also assign the conversion table to a Site (Level 3).
16. Click OK to save the Conversion Table. The Conversion Table will then be available for interpolation and use with other datasets.
17. You can construct the one conversion table from consecutive data ranges that vary in their modelled relationships. In this instance, you need to reiterate the process of including/excluding data points from the analysis and once each section is modelled, copying that regression data to the Output table.

Use the Calculation tool

Additional review of the ratings is available via the Calculation Tool. By executing two data conversions, you are able to calculate the difference between the two tables.