Mapping Alcatraz

Eloise McMinn Mitchell, Flyability 

Digitising the notorious prison

ALCATRAZ is a tiny island off the coast of San Francisco. In the 1930s, it was considered the most fortified and secure prison in the world.

Escape from this location was virtually impossible, which explains why it has been used as a prison of sorts for almost its entire history, including during the American Civil War in the 1860s.

However, in the 1960s, Alcatraz was decommissioned as a prison. Then in 1972 it was added to the Golden Gate National Recreation Area and opened for public tours in 1973.

Since then it has been under the management of the National Parks Service. Offering access to areas not safe for human entry, including confined spaces, the Elios 3 drone system, was selected by the client, VCTO Labs, to be utilised for the dungeons of Alcatraz.

With a dream to digitise an entire National Park in the United States of America, of which there are 63 ranging in size and purpose, this virtual national park would be created as a scientific resource that could be used for managing the island, identifying maintenance needs, and accessing dangerous locations that are not possible to reach safely.

It could also be a potential tool for tourists, providing digital access to locations currently closed to the public, as well as creating a resource that can be viewed from afar for people who cannot visit the site.

Finally, the environment and buildings on Alcatraz face the risk of decay and damage.

With rising sea levels combined with over a million visitors per year, the island is under significant pressure and faces threats from both people and climate change. The digital version of Alcatraz could help detect these issues, plan responses and identify stress points.

This could also include creating a resource that could be used for change detection. It took nine months to secure the specific permits necessary for the project, including a drone permit as drones are typically not allowed in national parks.

Drone mapping and surveying

The next spot it was used was behind a barred door. It was a thick, jailhouse-like barrier that had been sealed for decades. This structure is one of the oldest parts of the island, dating back to the civil war.

Drone-based lidar specialists, drone-based photogrammetrists, terrestrial laser scanners, people who used SLAM, plus more were needed to get this project underway.

Over the course of three weeks, data from every inch of Alcatraz’s rocky island and the buildings around it was gathered.

Without infrastructure to house guests in this National Park, the team even had to sleep in old jail cells.

With the intention to digitise the entirety of the island from top to bottom, the drone was used as a safe way to collect the necessary data to get the full picture of Alcatraz.

It made things more simple in a potentially dangerous environment as it can fit into spaces as small as 50x50cm while gathering both lidar and visual data to inform a detailed analysis of even the most hard-toreach areas.

All of the island needed to be digitised, from the inside out, including several structures which are currently shut to the public, and some even restricted from staff accessing them due to the potential safety risks.

The powerhouse stack

The old powerhouse on the island is currently shut down and off-limits to the public. It used to be where they generated all the electricity for the island, and has several hazards inside it.

There are two oil-fed boilers, chimneys and heating, ventilation and air conditioning (HVAC) systems.

The infrastructure ranges in age, with some of it being 100 years old. It was not possible to laser scan from the ground, or fit a typical rotary drone into the space.

The drone was the only tool that could safely gather the lidar data in this space. They also flew up the smoke stack in the power house, pictured above.

Civil War era dungeon

This project will be a first for the US and set an exciting precedent for creating digital versions of National Parks that can be used for education, outreach, research and park maintenance.

The next spot it was used was behind a barred door. It was a thick, jailhouse-like barrier that had been sealed for decades.

This structure is one of the oldest parts of the island, dating back to the civil war.

No one goes behind that door due to risk of dangerous chemicals or materials, as indicated by signs on the door.

However, carefully exploring this section with the drone revealed a Civil War era dungeon and a 3D model of it was created.

This was the first time anyone had seen this space in decades and made the archaeological team very excited.

Cisterns inspection

Finally, an inspection was done on some old cisterns. No one had been able to safely enter or inspect them for a long time, and it was hoped that there was a solution. The cisterns were accessed via two manholes on the northside of the island, which are rarely used. The structures are two huge concrete boxes buried underground, and the space between the ceiling of the box and the stagnant water is a maximum of four feet (just over 1m). More information about the piping network in and out of the cisterns was needed as there was no existing records to go off therefore the drone gathered a clear image of the space.

Setting a precedent

This project will be a first for the US and set an exciting precedent for creating digital versions of National Parks that can be used for education, outreach, research and park maintenance. This use of a variety of tools to achieve the overarching goal also demonstrates the exciting advancements we have made with modern technology. 

Eloise McMinn Mitchell, Flyability

www.flyability.com

@fly_ability

All images courtesy of Flyability.