Open to Sky

By Bhavana Priya B & Rashi Desadla IAAC (Institute for Advanced Architecture of Catalonia)

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Overview

Open to Sky maps sky visibility in New York City along pedestrian routes between public parks, overlaid with the Heat Vulnerability Index (HVI) — a neighbourhood-level measure of the likelihood of heat-related mortality.

High-rise density reduces sky visibility, intensifying the urban heat island effect, which directly correlates with higher HVI scores in those neighbourhoods.

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Core Concepts

Sky Visibility In a 2D orthogonal view of a city, what is not a building is sky. Sky visibility is therefore the inverse of building footprint and height — taller, denser buildings mean less sky.

Isovist Radius The visibility radius of the isovist at any point along the walk is a function of the average height of the buildings closest to the viewer's position on the shortest path between parks.

Heat Vulnerability Index (HVI) An index of the likelihood of someone from a neighbourhood to die due to excessive heat exposure. Visualised as circles on the map where the radius represents HVI intensity for each zip code.

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Data Pipeline

Source	Data
OpenStreetMap (OSM)	Buildings, streets, parks (extracted via bounding box)
NYC Open Data	Heat Vulnerability Index by zip code
Data.gov (USA)	2020 cartographic boundary shapefile with zip codes
QGIS	Joined zip codes to geo-coordinates
OpenAI	Generated CSV correlating zip codes to lat/long

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Workflow (Pseudocode)

1. Extract buildings, parks, streets from OSM using bounding box coordinates
2. Retrieve building heights and remap → invert to get sky visibility
3. Establish parks as start/end points and compute shortest walk between them
4. Find buildings closest to each point on the shortest walk → derive isovist radius
5. Generate isovist path and isovist boundary along the route
6. Load HVI CSV (zip code + HVI + lat/long) → project as points onto map
7. Draw circles per zip code where radius = HVI intensity

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Output

A map of lower Manhattan showing:

• Red line — shortest pedestrian route between public parks
• HVI circles — overlaid per zip code, radius proportional to heat vulnerability
• Isovist boundary — sky visibility envelope along the walk route

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Data Sources

1. OpenStreetMap
2. QGIS
3. NYC Heat Vulnerability Index Rankings
4. 2020 ZIP Code Tabulation Areas — Data.gov
5. OpenAI — used to generate a CSV correlating zip codes from (3) to geo-coordinates from (4)