To convert vector data to raster data in ArcMap, you will primarily use the "To Raster" toolset found within the Conversion Tools toolbox.
Here's a breakdown of the process:
1. Accessing the To Raster Toolset:
- Open ArcMap.
- Navigate to the "ArcToolbox" window. If it's not visible, go to "Geoprocessing" in the main menu and select "ArcToolbox."
- Expand the "Conversion Tools" toolbox.
- Expand the "To Raster" toolset. This is where you'll find the various tools designed for vector-to-raster conversion.
2. Choosing the Appropriate Tool:
The "To Raster" toolset offers several tools, each tailored to specific vector data types and conversion needs. Here are the most commonly used:
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Feature to Raster: This is a general-purpose tool suitable for converting point, line, or polygon features to a raster dataset. You'll need to specify which attribute field from the vector data you want to use as the cell values in the raster.
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Polygon to Raster: Specifically designed for converting polygon features to a raster dataset. Similar to "Feature to Raster," you select an attribute field to determine the cell values. This tool is optimized for polygon data.
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Point to Raster: Designed for converting point features to a raster dataset. Again, you'll select an attribute field from the point features to determine the cell values in the output raster.
3. Using the Selected Tool:
Let's use "Feature to Raster" as an example:
- Double-click the "Feature to Raster" tool to open its dialog box.
- Input features: Select the vector layer you want to convert.
- Field: Choose the attribute field from the vector layer that will determine the cell values in the raster. This field must be numeric.
- Output raster dataset: Specify the location and name for your output raster file. Ensure you include the file extension (e.g., "output.tif").
- Cellsize: Define the cell size (resolution) of the output raster. A smaller cell size will result in a finer resolution (more detailed) raster, but also a larger file size. Consider the scale of your analysis and the desired level of detail.
- Optional settings: The dialog provides options for assigning a cell assignment type or priority. These settings are typically not crucial for general conversions but may be relevant in specific cases where multiple features fall within the same raster cell.
- Click "OK" to run the tool.
4. Important Considerations:
- Cell Size: Choosing an appropriate cell size is critical. A cell size that is too large may result in the loss of important details from the vector data. A cell size that is too small may create an unnecessarily large raster dataset.
- Attribute Field: The choice of attribute field directly impacts the resulting raster's values. Select the field that represents the information you want to visualize or analyze in raster format.
- NoData Values: Areas where no vector features exist will be assigned a NoData value in the resulting raster. You can control the NoData value during the conversion process in some tools.
- Coordinate System: Ensure your input vector data and the ArcMap data frame are using the same coordinate system to avoid potential alignment issues.
- Data type of field: The chosen field should be a numeric type. Otherwise the tool could fail or produce unexpected results.
Example Scenario:
Imagine you have a shapefile of soil types (polygons) and an attribute field called "Suitability" that rates the suitability of each soil type for agriculture on a scale of 1 to 5. You would use the "Polygon to Raster" tool, selecting the soil type shapefile as the input, "Suitability" as the field, and defining an appropriate cell size. The resulting raster would then represent the spatial distribution of agricultural suitability, with each cell's value corresponding to the "Suitability" rating of the soil type in that location.
