Dark Skies: Light Pollution in San Diego...
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Dark Skies: Light Pollution in San Diego County Oliver Abbitt, Mariel Nelson, Grace Treffinger December 9, 2016 Client: Reuben H. Fleet Science Center and Planetarium Light pollution, or excess articifial light, is one of the most pervasive forms of environmental alteration by humans and obstructs visibility of the night sky from Earth’s surface. According to NOAA (2016), about 80% of Americans can no longer see the Milky Way. Using a light pollution dataset from the NOAA Earth Observation Group, we identify the most suitable locations for people to look at the night sky in urban San Diego County. The analysis provides information for use in an exhibit at the Fleet Science Center to make astronomy education more accessible and improve quality of life for as many interested residents as possible. Surface Analysis A 10 meter digital elevation model (DEM) was used to determine slope, aspect and peaks within the county. Slope allowed locations to be assessed based on accessibilty, with steep slopes being less favorable. Next, aspect was measured, with any slope facing northeast, east, or southeast considered positive because they faced away from coastal San Diego, the area’s main source of light pollution. Finally, peaks and hills were considered favorable viewing spots. These topographic highs were identified by inverting the DEM, isolating the lowest points using the “Sinks” tool in the ArcMap Hydrology toolset, and then re-inverting. Radiance (nw/cm2/sr) 2010 Census Tracts >32 16-32 8-16 4-8 2-4 1-2 0.5-1 0.25-0.5 <0.25 0 10 20 5 Miles Brightness, San Diego County Author: Oliver Abbitt, Dec 5, 2016 Projection and Dat u m: NAD83 California State Plane Zone VI, Feet Source: NOAA Earth Observation Group and SanGIS.org Slope Aspect Peaks Suitability Analysis Our suitability analysis was used to combine radiance values with other data about San Diego County to identify the most and least suitable places to view the night sky. Because the Fleet Science Center is geared toward students and people of all ages and abilities, we assumed that the best locations would be close to transportation routes and comfortable to access. We combined data from our surface model, NOAA, and SanGIS to produce a composite map of the constraints and opportunities for seeing stars in the San Diego County region, identifying points with minimal interference from light- and noise-generating objects. Opportunities Low radiance (<0.25-4 nw/cm2/sr weight 5 to 1) Public use areas (weight 5) Peaks (weight 3) Transit stops (buffer 2500 ft weight 1) Bike routes (buffer 1000 ft weight 1) Non-highway roads (Euclidean distance 2500 ft weight 3, 5000 ft weight 2) Less cloudy climate (interior and transitional zones weight 1) Low slope (0-10 degrees weight 2, 10-20 degrees weight 1) Aspect away from light pollution (E weight 2, NE and SE weight 1) Weather stations, educational value (buffer 5000 ft weight 1) Constraints High radiance (8->32 nw/cm2/sr weight -1 to -3) Airport noise and approach or “impact” zones (weight -2) Freeways (buffer 5000 ft weight -2) Highways (buffer 1000 ft weight -1) Evironmentally sensitive locations (weight -1) High slopes (30-90 degrees weight -2) Cell phone towers incorporated (buffer 1000 ft weight -1) Cell phone towers unincorporated (buffer 1000 ft weight -1) Cloudy climate (marine and coastal zones weight -2) National Forests (more trees, less sky visibility weight -1) Nighttime Brightness, San Diego County Author: Oliver Abbitt, December 5, 2016 Projection and Datum: NAD83 California State Plane Zone VI, Feet Source: NOAA Earth Observation Group and SanGIS.org Author: Oliver Abbitt, December 5, 2016 Projection and Datum: NAD83 California State Plane Zone VI, Feet Source: NOAA Earth Observation Group and SanGIS.org Suitability 2010 Census Tracts Total Weight -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 0 10 20 5 Miles Location Suitability for Stargazing Author: Mariel Nelson, December 5, 2016 Projection and Datum: NAD83 California State Plane Zone VI, Feet Source: NOAA Earth Observation Group and SanGIS.org Conclusions Location 7, which is also the highest peak in the City of San Diego, served the greatest population. Points with the highest suitability (15-19) were not close enough to highly populated areas be included in the final list of chosen facilities. Points that also satisfied the requirement of being easily accessible by car had medium-high viewing suitability (13-14). A logical next step of this project for the Fleet Science Center would be to analyze the zip codes where visitors live and compare this to the suitable locations, selecting some to focus on and potentially create an exhibit around. Comparison between accessibility and demographic data could also provide insightful results about who can more easily see a clear night sky, with applicable data about how to educate different student groups about space in a relatable way. The NOAA data had approximately 1500 foot grid resolution and the SanGIS vector data was converted during processing to 30 foot grid resolution. Viewing Locations Suitability Population Served 1 14 6,313 2 13 30,473 3 13 62,401 4 13 17,479 5 13 18,284 6 13 16,043 7 13 222,529 8 13 7,509 9 13 27,557 10 13 29,984 Optimal Stargazing Locations Network Analysis The location-allocation analysis was used to determine the ten most suitable viewing points that serve the largest population, where facilities were suitable points for viewing stars with weight >13 and demand points were the 2010 tract centroids weighted by population. We chose to maximize attendance in order to identify the ten most suitable viewing locations by travel time, no more than 20 minutes away. The resulting locations are accessible to 438,572 people in San Diego County. The table below shows the population served by each viewing location and the suitability (higher suitability being a better viewing location). Author: Grace Treffinger, December 5, 2016 Projection and Datum: NAD83 California State Plane Zone VI, Feet Source: NOAA Earth Observation Group and SanGIS.org, Constrained Network of San Diego by John Radke Ideal Viewing Locations Identify Population Served Radiance
Transcript of Dark Skies: Light Pollution in San Diego...
Dark Skies: Light Pollution in San Diego County
Oliver Abbitt, Mariel Nelson, Grace TreffingerDecember 9, 2016
Client: Reuben H. Fleet Science Center and Planetarium
Light pollution, or excess articifial light, is one of the most pervasive forms of environmental alteration by humans and obstructs visibility of the night sky from Earth’s surface. According to NOAA (2016), about 80% of Americans can no longer see the Milky Way.
Using a light pollution dataset from the NOAA Earth Observation Group, we identify the most suitable locations for people to look at the night sky in urban San Diego County. The analysis provides information for use in an exhibit at the Fleet Science Center to make astronomy education more accessible and improve quality of life for as many interested residents as possible.
Surface Analysis
A 10 meter digital elevation model (DEM) was used to determine slope, aspect and peaks within the county. Slope allowed locations to be assessed based on accessibilty, with steep slopes being less favorable. Next, aspect was measured, with any slope facing northeast, east, or southeast considered positive because they faced away from coastal San Diego, the area’s main source of light pollution. Finally, peaks and hills were considered favorable viewing spots. These topographic highs were identified by inverting the DEM, isolating the lowest points using the “Sinks” tool in the ArcMap Hydrology toolset, and then re-inverting.
Radiance (nw/cm2/sr)2010 Census Tracts
>32
16-32
8-16
4-8
2-4
1-2
0.5-1
0.25-0.5
<0.25
0 10 205 Miles
Brightness, San Diego County
Author: Oliver Abbitt, Dec 5, 2016Projection and Datu m: NAD83 California State Plane Zone VI, Feet
Source: NOAA Earth Observation Group and SanGIS.org
Slope
Aspect
Peaks
Suitability Analysis
Our suitability analysis was used to combine radiance values with other data about San Diego County to identify the most and least suitable places to view the night sky. Because the Fleet Science Center is geared toward students and people of all ages and abilities, we assumed that the best locations would be close to transportation routes and comfortable to access. We combined data from our surface model, NOAA, and SanGIS to produce a composite map of the constraints and opportunities for seeing stars in the San Diego County region, identifying points with minimal interference from light- and noise-generating objects.
Opportunities
Low radiance (<0.25-4 nw/cm2/sr weight 5 to 1)Public use areas (weight 5)Peaks (weight 3)Transit stops (buffer 2500 ft weight 1)Bike routes (buffer 1000 ft weight 1) Non-highway roads (Euclidean distance 2500 ft weight 3, 5000 ft weight 2)Less cloudy climate (interior and transitional zones weight 1)Low slope (0-10 degrees weight 2, 10-20 degrees weight 1)Aspect away from light pollution (E weight 2, NE and SE weight 1)Weather stations, educational value (buffer 5000 ft weight 1)
Constraints
High radiance (8->32 nw/cm2/sr weight -1 to -3)Airport noise and approach or “impact” zones (weight -2)Freeways (buffer 5000 ft weight -2)Highways (buffer 1000 ft weight -1)Evironmentally sensitive locations (weight -1)High slopes (30-90 degrees weight -2)Cell phone towers incorporated (buffer 1000 ft weight -1)Cell phone towers unincorporated (buffer 1000 ft weight -1)Cloudy climate (marine and coastal zones weight -2)National Forests (more trees, less sky visibility weight -1)
Nighttime Brightness, San Diego County
Author: Oliver Abbitt, December 5, 2016Projection and Datum: NAD83 California State Plane Zone VI, FeetSource: NOAA Earth Observation Group and SanGIS.org
Author: Oliver Abbitt, December 5, 2016Projection and Datum: NAD83 California State Plane Zone VI, FeetSource: NOAA Earth Observation Group and SanGIS.org
Suitability2010 Census Tracts
Total Weight-9
-8
-7
-6
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
0 10 205 Miles
Location Suitability for Stargazing
Author: Mariel Nelson, December 5, 2016Projection and Datum: NAD83 California State Plane Zone VI, FeetSource: NOAA Earth Observation Group and SanGIS.org
Conclusions
Location 7, which is also the highest peak in the City of San Diego, served the greatest population. Points with the highest suitability (15-19) were not close enough to highly populated areas be included in the final list of chosen facilities. Points that also satisfied the requirement of being easily accessible by car had medium-high viewing suitability (13-14). A logical next step of this project for the Fleet Science Center would be to analyze the zip codes where visitors live and compare this to the suitable locations, selecting some to focus on and potentially create an exhibit around. Comparison between accessibility and demographic data could also provide insightful results about who can more easily see a clear night sky, with applicable data about how to educate different student groups about space in a relatable way. The NOAA data had approximately 1500 foot grid resolution and the SanGIS vector data was converted during processing to 30 foot grid resolution.
Viewing Locations Suitability Population Served1 14 6,3132 13 30,4733 13 62,4014 13 17,4795 13 18,2846 13 16,0437 13 222,5298 13 7,5099 13 27,557
10 13 29,984
Optimal Stargazing Locations
Network Analysis
The location-allocation analysis was used to determine the ten most suitable viewing points that serve the largest population, where facilities were suitable points for viewing stars with weight >13 and demand points were the 2010 tract centroids weighted by population. We chose to maximize attendance in order to identify the ten most suitable viewing locations by travel time, no more than 20 minutes away. The resulting locations are accessible to 438,572 people in San Diego County. The table below shows the population served by each viewing location and the suitability (higher suitability being a better viewing location).
Author: Grace Treffinger, December 5, 2016Projection and Datum: NAD83 California State Plane Zone VI, FeetSource: NOAA Earth Observation Group and SanGIS.org, Constrained Network of San Diego by John Radke
Ideal Viewing
LocationsIdentify
Population Served
Radiance
