Fill NoData by IDW Interpolation
Overview
Inverse distance weighting (IDW) estimates unknown values from nearby known points, with closer points contributing more strongly. It is suitable for converting discrete observations into a continuous raster surface or filling raster gaps from nearby valid samples.
Use Cases
- Convert monitoring stations, sample points, or observation points into a continuous raster surface.
- Prepare spatially continuous inputs for temperature, rainfall, or pollutant-concentration analysis.
- Generate a regular grid before zonal statistics, threshold extraction, or map production.
Parameters
| Parameter | Description | Notes |
|---|---|---|
| Input vector file | Vector file containing interpolation points | Required |
| Interpolation field | Numeric field used for interpolation | Required |
| Power | Distance-decay power. Higher values increase the influence of nearby points | Required; default: 2.0 |
| Smoothing parameter | Smoothing parameter. 0 means no smoothing | Required; default: 0.0 |
| Search radius 1 | Search radius in the X direction. 0 means automatic calculation | Required; default: 0.0 |
| Search radius 2 | Search radius in the Y direction. 0 means automatic calculation | Required; default: 0.0 |
| Rotation angle | Rotation angle of the search area in degrees; counterclockwise is positive | Required; default: 0.0 |
| Maximum search points | Maximum number of search points. 0 means unlimited | Required; default: 0 |
| Minimum search points | Minimum number of search points. 0 means unlimited | Required; default: 0 |
| Include all touched pixels | Controls whether all touched pixels are included | Optional; default: False |
| Invert pixel selection | Controls whether pixel selection is inverted | Optional; default: False |
| Interpolation area | Coordinate system, resolution, and extent settings for the output raster | Optional |
| Output raster file | Output raster file | Required |
Steps
- Start the tool: Open Geoprocessing Toolbox → Spatial Analysis Tools > Raster Synthesis > Fill NoData, then start the Fill NoData by IDW Interpolation tool pane.
- Prepare input: Select the Input vector file, Interpolation field, and Interpolation area, then confirm that the data is complete and readable.
- Set core parameters: Configure Interpolation field, Power, Smoothing parameter, and search settings based on the analysis goal.
- Set output: Specify the Output raster file and confirm that the output path, format, and naming rules meet downstream requirements.
- Run and inspect the result: Click Run, then check whether the output value range, distribution, and raster extent meet expectations.
Notes
- IDW is sensitive to point distribution and outliers. Check source data before interpolation.
- Use a projected coordinate system when distance parameters are used; avoid treating longitude and latitude as planar distances.
- Sparse or unevenly distributed samples can reduce the reliability of the continuous surface.