I’ve always been fascinated with the rasters NASA put out showcasing night time illumination all over the world (called NASA’s Black Marble). More recently, I came across John Nelson’s blog Adventures in Mapping, where he has a fantastic post on leveraging NASA’s Black Marble images to create a single map comparing images of night time illumination from 2012 and 2016 to highlight where lights have increased and decreased.
I just loved the dark imagery of the map and how the man-made illumination stood out, and wanted to try and recreate a little bit of that myself as I begin diving deeper into ArcPro.
While I got my start in GIS work learning how to map in ArcMap in grad school and later continued learning while using ArcMap in internships and ArcOnline on the job, ArcPro is a bit of a different beast and once I got used to it, an immense improvement over ArcMap.
The main tool used to find the difference between night light illumination in the 2012 and 2016 NASA images is using the Raster Function ‘Minus’ to take the difference in raster pixel values. From there, its a matter of fussing with the symbology and adding in touches of design and labelling. My personal and academic interest was doing a close up study of the Southeast Asia Region, and highlighting where light pixel values increased and decreased.
Since this was my first dive into creating a map in ArcPro for a personal project, I wanted to do something that I had an interest in and could finish in a reasonable amount of time.
The resulting map has some stylistic differences from John Nelson’s original, mainly in adding in borders and different shading to make the different countries stand out from each other and using clear font and label placement to ensure a reader with little knowledge of the region could understand what and where they were seeing night light changes happening. I can already see some changes I need to make, such as adding additional labelling where the main part of Malaysia is, and the major islands that are part of Indonesia, but overall I’m pretty happy with the results for now.
Now that I have an initial map done (exported from ArcPro and finished in Adobe Photoshop), I plan on doing some research on understanding the why behind where night lights changed pixel value. As night lights have been found in several studies to be a good proxy for economic activity, I imagine there could be some interesting things to delve into.
Follow up to this post coming soon!