Raster Calculator in ArcGIS Pro
Perform complex raster operations using a simple, intuitive interface.
Enter the name or path of the first raster layer. Supports spatial datasets.
Enter the name or path of the second raster layer (optional, for specific operations).
Enter the name or path of the third raster layer (optional, for specific operations).
Use layer names in brackets like [DEM]. Standard math operators (+, -, *, /) and logical operators (>, <, ==, !=) are supported. See documentation for more.
Name for the new raster layer created by the calculation.
Value to represent NoData in the output raster. Leave blank for default.
Calculation Summary
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What is the Raster Calculator in ArcGIS Pro?
The Raster Calculator in ArcGIS Pro is a powerful geoprocessing tool that allows users to perform mathematical and logical operations on raster datasets. It enables the creation of new raster layers by combining existing ones, applying complex formulas, or evaluating conditions. This tool is fundamental for various spatial analysis tasks, including suitability modeling, change detection, and data manipulation.
Geoscientists, environmental planners, urban developers, and researchers commonly use the Raster Calculator. Misunderstandings often arise regarding the input format (layer names vs. file paths), the specific syntax for expressions, and the interpretation of raster algebra operators. Unlike simple calculators, the Raster Calculator works with entire datasets (rasters) where each cell is processed based on the defined expression.
It’s essential to understand that this tool operates on cell-by-cell basis. For example, if you are adding two rasters, the value of the cell at row X, column Y in the output raster will be the sum of the values of the cells at row X, column Y in the input rasters. This allows for sophisticated raster algebra.
Raster Calculator Formula and Explanation
The core of the Raster Calculator is the expression you define. This expression dictates how input raster values are processed to produce output raster values. The general form involves referencing input rasters (by name or path) and applying mathematical or logical operators.
Common Operators and Functions:
- Arithmetic: +, -, *, / (addition, subtraction, multiplication, division)
- Logical: >, <, >=, <=, ==, != (greater than, less than, greater than or equal to, less than or equal to, equal to, not equal to)
- Boolean: AND, OR, NOT
- Conditional: CON(condition, true_value, false_value)
- Mathematical: SQRT(), EXP(), LN(), LOG(), SIN(), COS(), etc.
Formula Structure:
[InputRaster1] or [InputRaster1]
Variables Table:
| Variable/Input | Meaning | Unit | Typical Range/Type |
|---|---|---|---|
| Raster Layer A/B/C | Input raster dataset(s) being used in the calculation. | Cell Value Units (e.g., meters, degrees, counts, classification codes) | Raster Dataset / Layer Name |
| Formula Expression | The mathematical or logical expression defining the raster operation. | Unitless (defines relationship between cell values) | String (e.g., “[DEM] * 0.5”, “[Landcover] == 3”) |
| Output Raster Name | The name assigned to the newly generated raster layer. | N/A | String |
| NoData Value | A specific value assigned to cells that have no data. | Same as input cell value units. | Number (Integer or Float) |
Note: Units depend entirely on the input raster data (e.g., elevation in meters, temperature in Celsius, classification codes).
Practical Examples
Example 1: Reclassifying Elevation Data
Scenario: You have an elevation raster named ‘DEM.tif’ and want to create a new raster classifying areas below 100 meters as ‘Lowland’ (value 1) and areas 100 meters or above as ‘Highland’ (value 2).
Inputs:
- Raster Layer A:
DEM.tif - Formula Expression:
Con([DEM.tif] < 100, 1, 2) - Output Raster Name:
elevation_zones
Calculation: The `Con` function checks each cell. If its value in 'DEM.tif' is less than 100, it assigns 1; otherwise, it assigns 2.
Results:
- Output Raster Name:
elevation_zones - Status: Calculation Complete (simulated)
- Operation Type: Conditional Reclassification
- Formula Applied:
Con([DEM.tif] < 100, 1, 2)
Example 2: Calculating Slope from Elevation
Scenario: You have an elevation raster 'DEM_meters.tif' and want to calculate the slope in percent. The Raster Calculator can directly use the built-in `Slope` function.
Inputs:
- Raster Layer A:
DEM_meters.tif - Formula Expression:
Slope( "DEM_meters.tif", "PERCENT_RISE") - Output Raster Name:
slope_percent
Calculation: The `Slope` tool (a specific function callable within Raster Calculator) calculates the slope for each cell based on its neighborhood. "PERCENT_RISE" specifies the output unit.
Results:
- Output Raster Name:
slope_percent - Status: Calculation Complete (simulated)
- Operation Type: Slope Calculation
- Formula Applied:
Slope( "DEM_meters.tif", "PERCENT_RISE")
How to Use This Raster Calculator
- Identify Input Rasters: Determine which raster layers you need for your analysis. Note their exact names as they appear in your ArcGIS Pro project or their full file paths.
- Define the Formula: Construct your expression. Use brackets `[]` around raster names (e.g., `[DEM]`). Employ standard arithmetic (`+`, `-`, `*`, `/`) or logical operators (`>`, `<`, `==`). For complex operations, use built-in functions like `Con()`, `CellStatistics()`, `Slope()`, `Aspect()`, etc. Refer to the ArcGIS Pro documentation for a full list of available functions.
- Specify Output Name: Enter a descriptive name for the new raster layer that will be generated.
- Set NoData Value (Optional): If your input rasters have specific NoData values, or if you want to define one for the output, enter it here. Otherwise, leave it blank.
- Click 'Calculate': The tool will simulate the execution and provide a summary status. In ArcGIS Pro, this action would run the geoprocessing tool.
- Reset: Use the 'Reset' button to clear all input fields and start over.
- Copy Results: Click 'Copy Results' to copy the summary information (output name, status, operation type, formula) to your clipboard.
Unit Considerations: Always be mindful of the units of your input rasters. Adding a temperature raster (Celsius) to an elevation raster (meters) without proper conversion will produce meaningless results. Ensure your formula respects the units of the data.
Key Factors That Affect Raster Calculator Operations
- Raster Resolution (Cell Size): Finer resolutions capture more detail but increase processing time and file size. Operations involving neighborhood analysis (like slope) are highly sensitive to cell size.
- Coordinate System: Ensure all input rasters share a compatible coordinate system, especially for distance-based calculations. Projected coordinate systems are crucial for accurate measurements.
- Data Type: Input rasters can be integer or floating-point. Operations on different data types might lead to rounding or precision issues. Floating-point rasters offer higher precision.
- NoData Values: Incorrectly handling NoData values can lead to errors or skewed results. The Raster Calculator respects NoData cells, typically propagating them unless explicitly handled in the formula.
- Formula Complexity: Very complex formulas with many layers and functions can be computationally intensive and may require significant processing time and memory.
- ArcGIS Pro Version and Licensing: Specific tool availability or performance may vary slightly between ArcGIS Pro versions. Ensure you have the necessary license level (e.g., Standard or Advanced) for certain geoprocessing tools invoked via the calculator.
- Syntax Errors: Typos in layer names, incorrect operator usage, or missing brackets will prevent the formula from executing correctly.
Frequently Asked Questions (FAQ)
A: Yes, you can often reference layer files or layer names from the Contents pane. ArcGIS Pro is usually smart enough to find the underlying raster dataset.
A: By default, ArcGIS Pro will resample (mosaic, clip, or align) the rasters to a common cell size and extent before performing the calculation. This can be controlled in the geoprocessing environment settings, but be aware it can affect results.
A: You must manually convert one of the rasters or ensure your formula accounts for the difference. For example, if Raster A is in meters and Raster B is in feet, you might multiply Raster B by 0.3048 before using it in a calculation with Raster A.
A: While the Raster Calculator itself is primarily for cell-by-cell operations, you can use its output as input for other tools like Zonal Statistics as Table or Zonal Statistics. Some specific functions like `CellStatistics` can perform aggregations over specified areas.
A: The `CellStatistics` function calculates a statistic (e.g., MEAN, MEDIAN, SUM, MIN, MAX, RANGE, STD) for each cell location across multiple input rasters. For example, `CellStatistics(["R1", "R2", "R3"], "MEAN")` calculates the average value for each cell across R1, R2, and R3.
A: Yes, you can use a mask. You can either set a mask in the geoprocessing environment settings or incorporate a conditional statement into your formula, like `Con([DEM] > 100, [DEM] * 1.1, [DEM])`, to only modify cells meeting a certain condition.
A: In ArcGIS Pro, when you run the tool, you specify the output raster name and location. The result is automatically added to your map and geodatabase or folder.
A: It's best suited for cell-by-cell operations or predefined function applications. For complex model building involving multiple sequential steps, geoprocessing models or Python scripting (ArcPy) are often more efficient and manageable.