Mapping the Subjective
Finding Sunsets with GIS.
Several days ago was the 25th annual GIS Day, a perfect time to recognize how GIS and modern geospatial technology has shaped the world and how we map it. It's become so central to contemporary scientific discourse that it's hard to overstate the miscellany of applications and analyses it empowers.
From using mapping technologies to discover lost civilizations (Handwerk, 2022) to keeping humanity informed and prepared for climate change (Kamel Boulos and Wilson, 2023), the uses for GIS within academia are well understood and appreciated. However, many are surprised to learn GIS can be used for personal and creative endeavors as well. John Nelson is an excellent example of how GIS fuels innovation in modern cartography and it doesn't take more than a few seconds of browsing ESRI's map gallery to recognize just how neat personal maps can be (like my favorite cataloging the journeys of Mittens ). This story map uses Suitability Modelling within ArcGIS Pro to determine the best locations within and nearby Hungry Mother State Park for viewing a sunset.
To start the analysis, we have to consider what goes into making a spot suitable for viewing a sunset. The conditions I arrived at are:
- Close to a road or hiking trail
- On relatively flat ground
- Provides a good view of the sun setting (i.e. it's not blocked by mountains or trees)
- Overlooks the surrounding countryside
Of course, there's a lot more that goes into watching a pretty sunset other than those 4 things but I figured they're the best place to start.
From The National Map , LIDAR data were downloaded for Hungry Mother and the immediate surrounding area.
The LIDAR points were processed into a Digital Elevation Model (DEM), showing bare earth elevation -
and a Digital Surface Model (DSM), showing elevation of surface features.
Hill shade was generated using the DEM and the position of the sun on November 20th, 2024, at an hour before sunset.
This layer specifies which areas would likely have the best views of the sun setting as golden hour begins.
To identify areas where trees or buildings block the view facing the sun, a new raster was derived where each cell was the max value of cells 250 units leftward in the DSM, representing the maximum height within 100m.
6 feet was added to the DEM and subtracted by the created raster. Positive values were extracted, representing areas where a 6'0 person can see at least 100m leftward with no obstructions.
(The vertical strip on the left represents areas where all values were positive due to NoData values 100m leftward and was excluded from the suitability model's extent.)
Slope was calculated from the DEM to identify flatter areas.
Road and trail data were accessed from OpenStreetMap using the OSMNX Python package.
A distance accumulation raster was created from road and trail data with slope raster surface costs.
A suitability model was created using each layer and weighted in the following order of preference:
- Unobstructed views 100m leftward
- Proximity to roads or hiking trails
- Hill shade
- Elevation
- Slope
The resulting suitability map is symbolized to show the most suitable areas as dark green and the least suitable as dark red.
Any dark green areas satisfy all the stated criteria for suitable sunset viewing locations (Though important to note, most dark green areas are on private property).
This analysis used LIDAR points and data from OpenStreetMap to create a suitability model for viewing sunsets near Hungry Mother State Park. Though, hopefully beyond that, it's an example of how GIS is an adaptable tool for more than just scientific endeavors. From tracking beloved neighborhood cats to discovering lost civilizations to finding a new place to watch sunsets, the entire world is waiting to be mapped.
Below is a series of photographs I've taken throughout the years near and within Hungry Mother overlayed on top of the suitability map.
Molly's Knob
Boat Ramp
CC Camp Trail
Mitchel Valley Summer
Overlook of Marion
A Hillside of Flowers
The Dam
Mitchell Valley Cows
A Saharan Sunset
Towards Tazewell at Dusk
A Snowy Overlook
References
Esri Map Gallery | Maps Created by Our Global User Community. (2024). Esri.com. https://mapgallery.esri.com/
Handwerk, B. (2022, May 25). Lost Cities of the Amazon Discovered From the Air. Smithsonian Magazine. https://www.smithsonianmag.com/science-nature/lost-cities-of-the-amazon-discovered-from-the-air-180980142/
Kamel Boulos, M. N., & Wilson, J. P. (2023). Geospatial techniques for monitoring and mitigating climate change and its effects on human health. International Journal of Health Geographics, 22(1). https://doi.org/10.1186/s12942-023-00324-9
Moore, J. (2018). Esri Map Gallery | Maps Created by Our Global User Community. Esri.com. https://mapgallery.esri.com/submission-detail/26305
Nelson, J. (n.d.). John Nelson Maps. YouTube. https://www.youtube.com/channel/UCpdwmy5JTFNUkKknxHH9Dsg
USGS. (n.d.). TNM Download v2. Apps.nationalmap.gov. https://apps.nationalmap.gov/downloader/
Virginia Department of Wildlife Resources. (2024). Hungry Mother State Park. Dwr.virginia.gov. https://dwr.virginia.gov/vbwt/sites/hungry-mother-state-park/