You may ask yourself, how did he make that beautiful map?

Building the Alaska topography map

Greg Fiske

February 17, 2023

The origin of any map is to have a reason to make the map in the first place. I was originally asked to make some maps of Alaska climate change hazards for the Arctic Report Card. Those maps went a different direction, but I decided to make best use of the data gathered for a general use map.

Let's zoom in to a small portion of Alaska, the region just east of Anchorage, and examine some data details.

As with any map, we start with getting the base layers correct.

Alaska has such beautiful topography it made sense to put some effort into making it a strong component of the map.

This is a standard off the shelf hillshade.

Same as it ever was...

Seeking a better route, I decided to follow a Nelson style ambient occlusion approach. The first step was to create some downsampled versions of our DEM data. This slide shows a 10x10 coarsened version of the Alaska 3DEP 200m DEM.

Step 2: downsampled 20x20

Step 3: downsampled to 50x50.

All of these steps are easily coded in your software/platform of choice.

In Earth Engine, for example: _{outImage = inImage.FocalMean(50,'circle','pixels')}

Or python in ArcGIS: _{outImage = FocalStatistics(inImage, "Circle 50 CELL", "MEAN", "DATA", 90)}

Next a hillshade is created on all the downsampled layers. Here's the 10x10

_{outImage = ee.Terrain.hillshade(inImage,315,45);}

A 20x20 version is also created and cumulatively blended with the previous.

Same with a 50x50 version. The changes are subtle, but excellent.

Then we do the same with Slope. Here's the 10x10

_{outImage = ee.Terrain.slope(inImage)}

20x20

50x50

Water dissolving and water removing.

Now the secret ingredient: A standard Sky Model Hillshade really brings out the valleys (check out this link to learn about this technique in either ArcGIS or QGIS software). Additionally, there's a pretty great description of Sky Model hillshades here .

And you may ask yourself, "Well, how did I get here? "

Answer: I baked all these layers together using blending options and we end up with something pretty spectacular.

Recall where we started.... roll back and forth a bit to compare.

Simultaneously, I had been working on this Alaska-wide cloud free Sentinel2 image mosaic.

Dark image mosaics like this have a purpose, they're good for fancy web pics and fundamental to our remote sensing analyses... but they're entirely unsuited for annotation or place labeling.

Those who are local may have noticed a slice of this map hanging around the Woodwell offices.

Or cameo appearances in Woodwell print media...

So the final stage was to combine all of these ingredients into one decorative, yet realistic, display. I used color-burn blending to add the true color mosaic to the hillshaded background (Photoshop, Blender, ArcGIS Pro, your choice, they all work). It definitely took some experimentation but the results are spectacular. Am I right, am I wrong?

So why go through all this just for a map?

Firstly, the results have proven to be both effective and multipurpose.

Whether we're decorating our walls, creating conference posters, puzzles, web or print material... A nice map always makes a great addition.

Secondly, it's no secret that we're in the Attention Economy.

Defined: "... The term reflects an acknowledgement that the human capacity for attention is limited and that the content and events vying for that attention far exceed that capacity ( source )." A pretty map often stands out... Inviting readers to learn more about your topic.

Lastly, maps are loved.

Maps invoke conversation and inspire story telling. This map is only one small feature in a large and growing arsenal of map products. Stay tuned for more.