on December 28, 2022

Displaying composite raster in colors other than RGB in ArcMap?

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Ditch the Default: Making Your Rasters Pop with Custom Colors in ArcMap

Okay, so you’re staring at a composite raster in ArcMap. Chances are, it’s decked out in the usual Red-Green-Blue (RGB), right? But here’s the thing: ArcMap can do so much more than just that basic color scheme. Whether you’re knee-deep in scientific analysis, crafting a thematic map that tells a story, or simply want a more eye-catching visual, diving into custom colors is where the real magic happens. Forget the standard – let’s unlock the full potential of your raster symbology!

First things first, let’s get on the same page about how ArcMap sees raster data. Think of rasters as a grid, like a digital checkerboard. Each square (or cell) holds a value – maybe it’s elevation, temperature, what kind of ground cover is there… you name it. Now, when you’re dealing with a multi-band raster, ArcMap automatically assigns each band to a primary color: Red, Green, or Blue. That’s how you get that composite image. But trust me, that’s just scratching the surface.

So, how do we break free from the RGB chains? ArcMap gives you a few cool tools to play with:

  • Band Swapping: This is the simplest trick in the book, but it can make a HUGE difference. Basically, you’re just re-wiring which band controls which color. Want Band 1 to show up as blue instead of red? No problem! Maybe Band 2 would look better as brown, and Band 3 as green? Go for it! This is awesome for highlighting specific spectral signatures in your imagery. I remember one time I was working with some satellite imagery of farmland, and by tweaking the band combination, I could instantly see which fields were the healthiest. To do this, in the Layer Properties, head to the Symbology tab and pick “RGB Composite.” You’ll see where you can manually assign each band to a Red, Green, or Blue channel. Easy peasy.

  • Color Maps: Painting by Numbers (But Way Cooler): Think of color maps as associating specific colors with specific data values. This is perfect for single-band rasters or when you’ve got distinct categories in your data. Imagine a land cover map where “forest” is green, “water” is blue, and “urban” is gray. ArcMap lets you create and import these color map files (.clr) to bring your vision to life. You can whip up a .clr file straight from the Raster Properties dialog box. To use them, jump to the Symbology tab and choose either “Unique Values” or “Classified.”

  • Stretched Renderer + Color Ramps: Smooth Gradients for the Win: For those continuous raster datasets – things like elevation or temperature – the “Stretched” renderer and color ramps are your best friends. Color ramps are basically gradients of colors that smoothly transition across your data’s range. ArcMap comes loaded with some built-in ramps, but the real fun starts when you create your own using the Style Manager. I’ve spent hours tweaking color ramps to get just the right look for elevation maps. It’s addictive! To get started, in the Symbology tab, select “Stretched.” Then, pick a color ramp from the dropdown or right-click the ramp and hit “Properties” to customize it.

  • Raster Attribute Tables: Data-Driven Colors: Now, if your raster has a value attribute table attached, you can actually use the data in that table to drive your colors. It’s like saying, “Hey ArcMap, color these pixels based on the values in this column!” This is super powerful for thematic mapping. In the Symbology tab, click either “Unique Values” or “Classified,” then use the “Value Field” dropdown to pick the column you want to use.

    • Speaking of creating your own color ramps, let me give you the lowdown:

  • Go to Customize > Style Manager.
  • Expand your personal profile.
  • Click on that “Color Ramps” folder.
  • Right-click in the right panel, choose “New,” and then “Multi-part Color Ramp.”
  • Add Algorithmic Color Ramps and double-click each to pick your exact colors.
  • Give your masterpiece a name and close the Style Manager.

    • Now, a quick word on picking the right colors. It’s not just about what looks pretty!

    • Know Your Data: Pick colors that make sense for what you’re showing. Think sequential colors for continuous data, diverging colors for data with a critical midpoint.
    • Color Brewer is Your Friend: Seriously, check out colorbrewer2.org. It’s got palettes designed to be colorblind-safe and visually appealing.
    • Think About Your Audience: Make sure your colors are easy to understand for whoever’s looking at your map.
    • Contrast is Key: Make sure there’s enough contrast so that different features stand out.

    Bottom line? Ditching the default RGB and diving into custom colors is a game-changer in ArcMap. By mastering these symbology options and getting creative with color ramps, you can transform your rasters into powerful visual stories. So go ahead, experiment, and unleash your inner cartographer!

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