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How to symbolize & label Lidar raster layer in legend? What is 0-255?

Bud

ArcGIS Pro 3.4.2

A while back, I made a map that had a greyscale Lidar DTM raster in it, and included the Lidar layer in the legend.

When I look back at the map, I'm wondering if the 0-255 label in the legend is perhaps not very useful. Does 0-255 pertain to color values, not elevation values? Would it have better to somehow show what colors pertain to corresponding elevations?

What's the proper way to show a Lidar raster in a legend? Or is it better to leave it out of the legend? It’s been roughly 10-15 years since I made a proper PDF map, so I’m rusty.

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DanielFox1

Hi @Bud

Bit depth capacity for raster dataset pixels

The bit depth (pixel depth) of a pixel determines the range of values that a particular raster file can store, which is based on the formula 2n (where n is the bit depth). For example, an 8-bit raster can have 256 unique values that range from 0 to 255.

https://community.avid.com/forums/t/88124.aspx#:~:text=Digital%20component%20video%20(YCrCb)%20is,data%20is%200%2D1024).

You should be able to right click the layer and alter the symbology of the layer.

Imagery appearance

Raster bands

I hope the above documentation provides some further context to Imagery for you.

Bud

@DanielFox1 Thanks. Do you get the sense people usually leave rasters out of the legend, since the bit gradient isn’t very useful in terms if interpreting the map and knowing what a given raster color/value represents?

DanielFox1

Hi @Bud

Including a legend in your map to show the elevation of your Digital Terrain Model (DTM) is a great idea! It helps viewers understand the elevation changes and makes the map more informative. Here are some steps to create a legend for your DTM:

Choose a Color Scheme: Select a gradient or colour ramp that represents different elevation levels. Common choices are shades of green to brown or blue to red.
Define Elevation Ranges: Determine the elevation ranges that each colour represents. For example, 0-100 meters, 100-200 meters, etc.
Label Clearly: Ensure the legend is clearly labelled with elevation values and units (e.g., meters or feet).
Position the Legend: Place the legend in a visible but unobtrusive part of the map, such as the bottom corner.

Bud

Thanks. I’m planning to submit an idea: “Raster legend labels: Make raster values (like elevation) the default, not the color bit numbers”. Does that idea make sense? Like I mentioned, I’m rusty with rasters and cartography.

Bud

@DanielFox1 Also, another idea:

“Continuous raster symbology in map, but discrete color swatches as legend”

Map:

Legend:

Image source: https://gis.stackexchange.com/questions/388154/how-to-get-back-discrete-raster-legend-symbols-in-qgis-3-16

Does that idea make sense?

Edit: @JesseWickizer Do you see any obvious issues with this draft idea before I post it publicly? Thanks.

Bud

Idea: Raster legend labels — Make raster values like elevation the default, not the color bit numbers

Jesse Wickizer

@Bud you can do something similar with stretch raster symbology by using the Advanced Labeling settings.

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