Extract Raster by Attributes
Overview
Extract Raster by Attributes filters and extracts cells from an input raster according to a user-defined logical expression. Each raster cell has a value, and the tool evaluates the condition cell by cell. Cells that match the condition can keep their original values or receive a specified value; cells that do not match are written as NoData or ignored, producing an output raster that contains only the target cells.
Use Cases
- Remote sensing and land-use analysis: extract cells whose land-use class value represents cropland for area statistics or temporal change analysis.
- Environmental quality assessment: extract areas where AQI or PM2.5 raster values are greater than 75 μg/m³ to locate pollution hotspots.
- Vegetation and ecological monitoring: extract high-vegetation-cover areas, such as NDVI > 0.4, for ecological assessment.
- Hydrology and meteorology analysis: extract rainfall areas greater than or equal to 100 mm for flood-risk analysis.
- Geohazard risk assessment: extract areas where slope values are greater than 30 degrees for landslide susceptibility analysis.
Parameters
| Parameter | Description | Notes |
|---|---|---|
| Input raster file | Source raster whose cells will be filtered by the logical condition | Supports single-band or multiband rasters, including common formats such as .tif (GeoTIFF), .img (ERDAS IMG), and .asc (ASCII Raster). The input should have valid spatial reference information. |
| Extraction method | Logical operator for the cell value, used to define the filtering condition | Common operators include greater than, less than, equal to, greater than or equal to, less than or equal to, and not equal to. Range conditions, such as 10 <= value <= 50, or logical combinations, such as value > 30 AND value < 80, may also be supported. |
| Extraction value | Numeric threshold used with the extraction method to define the value range | The value type should be consistent with the cell value type of the input raster. |
| Output path | Target directory for the result raster file | Ensure that the directory exists and is writable. Avoid Chinese characters, spaces, and special symbols in the path for better cross-platform compatibility. |
| Output file name | Full result raster file name, including extension | The extension determines the output format, such as .tif for GeoTIFF or .img for ERDAS IMG. Avoid spaces and special characters in the file name. |
Steps
-
Start the tool
Open Spatial Analysis Tools > Extraction Analysis, then double-click Extract Raster by Attributes to start the tool pane.
-
Select the input raster file
- Input raster file: enter
dem.tif.
- Input raster file: enter
-
Configure the extraction condition
- Extraction method: select Greater than.
- Extraction value: enter
1000.
-
Specify the output location
- Output path: set the output to
User Space/Toolbox/Spatial Analysis Tools. - Output file name: enter
attribute.tif.
- Output path: set the output to
-
Run the tool
- Click Run at the bottom of the pane and wait until the task list reports that the tool has succeeded.
Notes
- Logical expression check: validate expression syntax before running to avoid runtime errors. For multiband operations, make sure the band count matches the fields referenced in the expression.
- Data type: the input raster can be integer or floating point. Pay attention to type conversion during comparison.
- NoData and boundary values: NoData cells do not participate in calculation by default and remain NoData in the result. Convert NoData to valid values first if they need to participate in logical operations.
- Output format: GeoTIFF (
.tif) is recommended. Compression such as LZW or DEFLATE can reduce storage size.