Legends with Unique Values symbology

Updated

Simplify the representation of complex datasets by utilizing Surfer’s Unique Values symbology and automated Legends. Categorical data (such as lithology types, land use classifications, or environmental zones) requires distinct visual identifiers rather than a continuous color gradient. This workflow allows you to assign unique colors and patterns to specific attributes within your base layers, ensuring that your map remains both mathematically accurate and visually intuitive.

By integrating automated legends with unique value mapping, you can eliminate manual labeling and ensure your map's key updates instantly as your data changes. This guide covers the end-to-end process of defining categorical symbology and generating professional legends for your spatial projects.

Topics covered in this article:

Categorical Symbology Overview

Creating Base Layers with Unique Value Symbology

Generating and Customizing Automated Legends

Legend Troubleshooting & Optimization

Categorical Symbology Overview

Visualizing non-numeric data requires a categorical approach where each unique entry in your attribute table receives its own distinct symbol or fill. For example, a map of regional lithology might require unique colors for "Basalt," "Sandstone," and "Shale," while an environmental map might distinguish between "Wetlands" and "Industrial Zones."

The Unique Values symbology tool allows you to automatically scan your data for these keywords and assign them consistent visual properties. This overview explains how Surfer interprets your attribute table to create a cohesive visual language for your map, moving beyond simple color scales to true categorical classification.

Legend options include: 

  • Creating a name for the Unique Values attribute for use in the legend, and using the \name directive in the legend template
  • Option for displaying only the properties that are applied in the layer
  • Option for changing the line or symbol sample size in the legend
  • For polygons, putting the line style around the fill sample (aka patch), using the \linefill directive in the legend
  • Setting the alignment for the samples to be left, center, or right
  • Option for separating samples on different rows (e.g. if an attribute had both a polygon and polyline feature, they could be displayed on one row in the legend, or separated onto two rows)
LegendUniqueValues.png

Legends for unique values symbology that were once hard to read are now easy to understand!

Creating Base Layers with Unique Value Symbology

Setting up a base layer with unique values is the foundation of a clear geological or thematic map. Instead of manually coloring dozens of polygons or points, you can use the Symbology properties to bulk-assign colors based on a specific attribute column. The steps below walk you through selecting your data source, choosing the correct attribute field, and applying a color scheme that maximizes contrast between categories. Whether you are dealing with a handful of rock types or hundreds of parcel IDs, this automated workflow ensures your data is represented accurately and efficiently.

Creating Base Layers with Unique Value Symbology - Step-by-step

  1. Click Home | New Map | Base
  2. Navigate to the Surfer Samples file in the installation directory (by default ), select NV2010.GSB and click Open.
  3. Let's convert a couple of the polygons into polylines, just for the sake of this exercise.
    1. In the Contents window, expand the Base layer, click on the first Polygon in the list, hold the CTRL key down and click on the second polygon in the list.
    2. Right click over the selection and click Change To | Polyline.
  4. To apply the symbology, select the Base layer in the Contents window.
  5. In the Properties window, on the General page, click Edit Symbology.
  6. In the Symbology dialog, select Unique Values from the list on the left.
  7. Change the Attribute field to Secondary, and then click the Add All toobar button. All the counties of Nevada are added to the table.

  8. You can see the line, fill, symbol, value and name. Set any line and fill properties you wish (or just accept the defaults). The Value is the attribute value from the data. You cannot change this. However, you can change the Name. The Name is what will show in the legend, by default. The name may or may not be the same as the actual attribute value. Go ahead and change some of the names for some of the attributes.

    1. Symbology.png
  9. Once you are satisfied with the changes, click OK. The properties are applied to the map.

Generating and Customizing Automated Legends

A map is only as useful as its legend. When using unique values, Surfer can automatically generate a Legend that dynamically pulls its labels and symbols directly from your base layer's properties. This ensures that if you change a color or rename a category in your data, the legend updates instantly. This section covers how to add a legend to your plot, customize the label formatting, and organize the layout to handle large numbers of categories. Learn how to toggle visibility for specific classes and adjust legend scaling to ensure your final output is professional and easy to read.

Generating and Customizing Automated Legends (Step-by-step)

  1. Select the base layer and click Map Tools | Add to map | Legend.
  2. By default the legend is created below the map. Go ahead and click and drag to move it to the side of the map. You can see that by default:
    1. The line samples are in the same column as the fill samples (aka. patches)
    2. The names are displayed next to the samples instead of the attribute value for the symbology

    3. The line style is surrounding the fill sample for the polygons, instead of displaying next to it

      2. legend.png
  3. In the Contents window, select the Legend.
  4. In the Properties window, click the Layers tab. Here you can play with some of the other additions, such as the Line sample size and the Sample alignment. The symbol size and separating samples do not quite apply to this example.
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Golden Nugget : Please note when using Separate samples on different rows, you may need to adjust your Template to account for the changes.

For example, if the template was \linefill \symbol \name and you separated the samples, the name would just be next to the symbol. You would want to include the name for each properties on each row: \linefill \name \symbol \name

Legend Troubleshooting & Optimization

As datasets grow in complexity, managing the legend's visual footprint becomes essential. If your legend contains dozens of entries, use the following techniques to maintain clarity:

  • Hiding Unused Classes: If your base layer contains categories that are not present in the current map view, you can toggle their visibility in the Legend Properties to keep the key concise.

  • Renaming for Clarity: You don't need to change your raw data to have clean labels. Use the Label column in the Symbology dialog to create user-friendly names (e.g., change "UNIT_4B" to "Lower Limestone").

  • Column Layouts: For legends with many unique values, switch from a single vertical list to multiple columns within the Legend properties to save vertical space on your plot.

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Golden Nugget : Linking Legends to Multiple Layers. A single legend in Surfer can represent multiple layers. If you have a 3D Drillhole layer and a Base Map layer both using the same lithological keywords, you can "Sync" them to a single legend. This ensures that "Sandstone" is represented by the same color and symbol across your entire project, providing a unified visual experience.

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