ArcGIS Pro Tutorial: Create Fishnet or Sampling Grids in ArcGIS Pro
Credit: Youtube Channel “Terra Spatial”
You can see all the tutorials from here: Techgeo Academy.
Creating fishnet or sampling grids is a fundamental skill in GIS analysis that allows you to divide your study area into systematic rectangular cells for sampling, analysis, or visualization purposes. This comprehensive tutorial will guide you through the process of creating fishnet grids in ArcGIS Pro using multiple approaches.
Method 1: Using the Create Fishnet Tool
Step 1: Access the Create Fishnet Tool
To begin creating your fishnet grid, follow these steps:
- Open ArcGIS Pro and load your project
- Navigate to the Analysis tab in the ribbon
- Click on Tools to open the Geoprocessing pane
- Search for “Create Fishnet” in the search box
- Select the Create Fishnet tool from the results
Step 2: Configure Fishnet Parameters
The Create Fishnet tool requires several key parameters to be set:
- Output Feature Class: Specify the location and name for your new fishnet feature class
- Template Extent: Define the spatial extent of your fishnet grid
- Origin Coordinate: Set the starting point for your grid (bottom-left corner)
- Y-Axis Coordinate: Define the orientation (typically 0,1 for north-up grids)
- Cell Width: Specify the width of each grid cell
- Cell Height: Specify the height of each grid cell
- Number of Rows: Optional – specify if you want exact dimensions
- Number of Columns: Optional – specify if you want exact dimensions
Step 3: Set Advanced Options
Additional configuration options include:
- Geometry Type: Choose between POLYGON, POLYLINE, or POINT
- Template Dataset: Use an existing feature class to define extent
- Label Features: Create point features at the center of each cell
Step 4: Execute the Tool
After configuring all parameters:
- Review all settings carefully
- Click Run to execute the tool
- Monitor the progress in the Geoprocessing pane
- Once complete, the new fishnet layer will be added to your map
Method 2: Using a Template Dataset
For more precise control over your fishnet extent, you can use an existing feature class as a template:
- In the Create Fishnet tool, browse to your template dataset
- The tool will automatically calculate the extent based on the template
- Adjust cell size as needed for your analysis requirements
- Run the tool to generate your fishnet grid
Practical Tips and Best Practices
- Coordinate System Consistency: Ensure your fishnet uses the same coordinate system as your study area
- Cell Size Selection: Choose appropriate cell dimensions based on your analysis scale and requirements
- Performance Considerations: Large fishnets with many cells can impact performance; consider your hardware capabilities
- Boundary Handling: Cells may extend beyond your study area; use clip operations if necessary
- Label Points: Enable label features if you need centroids for sampling or analysis
Common Applications of Fishnet Grids
- Ecological Sampling: Systematic sampling of wildlife habitats or vegetation surveys
- Urban Planning: Grid-based analysis of land use or development patterns
- Environmental Monitoring: Regular monitoring of water quality or air pollution
- Agricultural Analysis: Field sampling or crop monitoring
- Statistical Analysis: Spatial aggregation of point data or demographic information
Frequently Asked Questions
What coordinate system should I use for my fishnet?
Your fishnet should use the same coordinate system as your study area or analysis requirements. For accurate measurements, use a projected coordinate system rather than geographic coordinates (latitude/longitude).
How do I create a fishnet that matches my study area exactly?
Use the “Template Dataset” option in the Create Fishnet tool and select your study area boundary as the template. This will ensure your fishnet extent matches your area of interest precisely.
Can I create irregularly shaped grids instead of rectangles?
The Create Fishnet tool specifically creates rectangular grids. For irregular shapes, you would need to use other tools like Thiessen polygons, hexagonal grids (using custom tools), or manually create custom polygon grids.
Why are my fishnet cells not square even though I set the same width and height?
This typically occurs due to coordinate system distortion. If you’re using a geographic coordinate system (degrees), equal degree measurements don’t translate to equal distances. Switch to a projected coordinate system for accurate square cells.
How can I limit my fishnet to only cover land areas?
Create your fishnet with a larger extent, then use the Clip tool to intersect it with your land boundary polygon. This will remove cells that fall outside your area of interest.
What’s the difference between polygon, polyline, and point fishnet outputs?
Polygon creates filled rectangular polygons, polyline creates the grid lines only, and point creates points at the intersection or center of would-be grid cells. Choose based on your analysis needs.
Is there a limit to how many cells I can create in a fishnet?
While there’s no hard limit, very large fishnets can cause performance issues and large file sizes. Consider your computer’s memory and your analysis requirements when determining grid size.
How do I create hexagonal grids instead of rectangular ones?
ArcGIS Pro doesn’t have a built-in hexagonal fishnet tool, but you can use third-party tools, create custom Python scripts, or use the “Create Hexagons” tool available in some extensions.
Conclusion
Creating fishnet grids in ArcGIS Pro is an essential skill for GIS professionals involved in systematic sampling, spatial analysis, and data organization. By mastering the Create Fishnet tool and understanding its various parameters, you can efficiently generate grids tailored to your specific analytical needs. Remember to consider coordinate systems, cell sizes, and performance implications when creating large grids, and always validate your results to ensure they meet your project requirements.
With practice and experimentation with different parameters, you’ll be able to quickly generate fishnet grids for a variety of applications, from environmental monitoring to urban planning and everything in between.
