Filtering the input data removes null values/ranges from the input data source and also implements data capping.
If you have huge dataset but you wish to perform interpolation on the selected data only, you can use data conditioning. The data conditioning and grouping are pre-processing options, which means they are configured before performing the interpolation to create raster data.
Gridding or interpolation is always performed on the numeric data. If you have your data in TAB file format, you can browse and identify the numeric columns on which you want to perform interpolation. After you select one or more columns for interpolation, you can apply filtering on the data in the selected column. You can then group the data for better analysis.
You can filter input data by clicking the 
button on the Create Raster dialog. Filtering the
input data enables you to clean the input data by removing invalid data from input dataset. You
can specify a null value or a range of invalid data, with upper and lower caps, to exclude the
specified data from the gridding process. The filtering only applies to valid input data. If any
of the fields in the input dataset for a given point (i.e., X, Y or the field values) has a null
(or missing) value then the entire point is discarded. Filtering data also allows you to clip the
input dataset.
For data filtering, you have the following options.
Output Bands
It shows the list of input data column you have selected for gridding. The output raster will have as many bands as the number of columns. It enables you to either apply same conditions for all bands or work on individual bands.
- Apply same Condition for All Bands - Select this option if you want to apply same data conditioning for all bands. Each column that you select for interpolation becomes a band in the output raster. When selected, same data conditioning is applied to all input data columns.
- If you clear this option, Output Band displays so that you can set data conditioning for individual bands. This allows you to control input data conditioning on a per band basis.
Data Conditioning Options
To apply data conditioning on your input data, you need to first select the data columns in your TAB file. The gridding is performed on the selected data only. If you have a multi-band raster, you can apply data conditioning either for all bands or individually for the selected band.
You can control input data conditioning on a per-band basis.
You can combine following options to meet your input data filtering need:
- Specify Invalid Data - Select this option to enter one or more value
that you want to ignore during the interpolation. You need to identify specific values from
input dataset that you want to replace with null value. For example, if you have a value -20 in
the input data and that you want to ignore and replace it with null.
- Specify Invalid Values - Here you can specify a list of values that you want to ignore. Click Insert Row to add a new row to enter your value. Click Delete Row to delete a row.
- Specify Invalid Ranges - Here you can specify a range of values that you want to ignore. The specified range will be replaced by null values. For example, if you have a range of values from 1 to 20 elevation heights in the input data and you want to ignore these values and replace them with null so that you can create a grid for all values greater than 20.
- Convert Null to background - Select this option to convert null values to background value.
- Cap to Maximum - Select this option to prevent outlier values in the dataset from being included in the gridding process. For example, a maximum cap value can be set for gold assays which occur in mineralization systems prone to nugget effects.
- Cap to Minimum - Select this option to remove very low values which may unduly influence the cell values in the output grid.
You can set data capping to remove very high or very low values to remove samples which may unduly influence the cell values in the output grid.
Click OK to go back to the main window.
Coordinate (spatial) Data Conditioning Options
Filtering of input dataset can also be done by clipping a region out of entire dataset. To perform spatial data conditioning, you can filter data based on the rectangle or polygon drawn on the map. The gridding will be performed on the selected data only.
- Clip Region - Select either Polygon or Rectangle from the list. You can also draw a rectangle on the map and select it.
- Action - Select either Retain Inside or Retain Outside from the list.
- Polygon - You can provide a TAB file of polygon(s) to clip the output raster to the polygon boundaries. You can specify whether to clip a region outside or inside the raster bounds. However, it does not support polygons with holes.