ArcGIS Pro Tutorial: How to Use Raster Calculator in ArcGIS Pro for Spatial Analysis
Credit: Youtube Channel “Terra Spatial”
You can see all the tutorials from here: Techgeo Academy.
The Raster Calculator in ArcGIS Pro is a powerful tool that allows GIS professionals to perform complex spatial analysis by creating and executing mathematical expressions on raster datasets. This tutorial will guide you through the essential steps of using Raster Calculator for various spatial analysis tasks.
Prerequisites
- ArcGIS Pro installed and licensed
- Raster datasets loaded in your project
- Spatial Analyst extension enabled
- Basic understanding of raster data concepts
Accessing Raster Calculator
To open the Raster Calculator in ArcGIS Pro:
- Open your ArcGIS Pro project
- Navigate to the Analysis tab in the ribbon
- In the Geoprocessing group, click on Tools
- Search for “Raster Calculator” in the geoprocessing pane
- Alternatively, you can find it in Image Analysis window under the Raster Functions tab
Raster Calculator Interface Overview
The Raster Calculator window consists of several key components:
- Expression Box: Where you build your mathematical expressions
- Layers and Variables List: Shows available raster datasets
- Functions: Mathematical and logical functions for raster operations
- Output Raster: Specify the location and name for your result
- Environment Settings: Control processing extent and cell size
Basic Mathematical Operations
Raster Calculator supports fundamental mathematical operations:
- Addition: Con(“Raster1” + “Raster2”)
- Subtraction: Con(“Raster1” – “Raster2”)
- Multiplication: Con(“Raster1” * “Raster2”)
- Division: Con(“Raster1” / “Raster2”)
- Exponents: Con(“Raster1” ** 2)
Conditional Operations
Use conditional statements for advanced spatial analysis:
Basic Conditional Expression:
Con(("Elevation" > 1000), 1, 0)This expression assigns value 1 to cells where elevation exceeds 1000 meters, and 0 elsewhere.
Multiple Conditions:
Con(("Slope" < 10) & ("Aspect" >= 90) & ("Aspect" <= 270), 1, 0)This identifies areas with gentle slopes facing specific directions.
Practical Examples
Example 1: Normalized Difference Vegetation Index (NDVI)
(Float("NIR_Band") - Float("Red_Band")) / (Float("NIR_Band") + Float("Red_Band"))Example 2: Temperature Conversion
("Temperature_Fahrenheit" - 32) * 5/9Example 3: Weighted Overlay Analysis
("Slope" * 0.3) + ("Aspect" * 0.4) + ("Distance_to_Road" * 0.3)Best Practices and Tips
- Always ensure raster datasets have the same spatial reference system
- Use the Float() function to maintain decimal precision in calculations
- Set appropriate environment settings for processing extent and cell size
- Break complex expressions into smaller steps for easier debugging
- Use meaningful variable names for better expression readability
- Test expressions on small subsets of data before full processing
Common Functions in Raster Calculator
| Function | Description | Example |
|---|---|---|
| Con() | Conditional function | Con("Raster" > 100, 1, 0) |
| SetNull() | Set values to NoData | SetNull("Raster" < 0, "Raster") |
| IsNull() | Identify NoData cells | Con(IsNull("Raster"), 0, "Raster") |
| Float() | Convert to floating point | Float("Integer_Raster") |
| Int() | Convert to integer | Int("Float_Raster") |
Frequently Asked Questions
What is the syntax for using raster datasets in expressions?
Raster datasets should be enclosed in double quotes when used in Raster Calculator expressions. For example: "Elevation_Raster" or "Landuse_2020".
How do I handle NoData values in my calculations?
Use the SetNull() function to explicitly handle NoData values, or use IsNull() to identify and replace them. For example: Con(IsNull("Raster"), 0, "Raster") replaces NoData with 0.
Why am I getting an error about incompatible raster extents?
This occurs when input rasters have different spatial extents. Adjust the environment settings to set a common processing extent, or resample your rasters to match extents before calculation.
Can I use multiple conditional statements in one expression?
Yes, you can nest Con() functions or use logical operators (& for AND, | for OR) to create complex conditional expressions with multiple criteria.
How do I save my Raster Calculator expressions for future use?
Copy and paste your validated expressions into a text file or documentation. You can also save your entire ArcGIS Pro project which preserves the geoprocessing history including Raster Calculator operations.
What is the difference between Raster Calculator and Map Algebra?
Raster Calculator is a graphical interface tool that implements Map Algebra syntax. Map Algebra is the underlying mathematical framework, while Raster Calculator provides a user-friendly way to execute Map Algebra expressions.
How can I improve performance when working with large raster datasets?
Consider using appropriate pyramid levels, setting smaller processing extents, using smaller cell sizes only when necessary, and ensuring sufficient system memory. Also, break large processing areas into manageable chunks.
Conclusion
The Raster Calculator in ArcGIS Pro is an indispensable tool for GIS professionals performing spatial analysis. By mastering its capabilities, you can create sophisticated analytical models, perform complex mathematical operations on raster data, and generate meaningful insights from your spatial datasets. Remember to follow best practices, understand the functions available, and always validate your results for accuracy.
Regular practice with various datasets and expressions will enhance your proficiency with Raster Calculator, making it a powerful addition to your GIS toolkit for advanced spatial analysis tasks.
