Helmdar: 3D Scanning Brooklyn on Rollerblades

Summary

Helmdar: 3D Scanning Brooklyn on Rollerblades 2025 May 4 One of my favorite joys is exploring a city late at night on rollerblades. I’ve been doing it fairly regularly for about 10 years now, first in Boston and then in NYC. Every time day turns to night and back again a city takes a breath. At night people flow out or huddle up in buildings, leaving the streets clear for the people and machines that reset the urban environment for the next day. Garbage trucks lumber about, workers unload fresh stock at stores, repairs happen in subway tunnels and on roads. Without all the people it’s easier to see the naked form of the streets, buildings, and infrastructure. When you’re moving slow you spend more time taking in the details. When you’re moving fast the world becomes a blur. The world around you is a brush that paints into your perception, and the speed of the brush strokes helps set the style of the painting. I like rollerblading in particular because it gives those perceptual brush strokes a lot of range. You can quickly stop and soak in a detail, change direction, occupy a tight space, or fly downhill in a long straight line. Stickdar Some years ago I picked up a 2D LiDAR scanner (RPLidar A1) without a particular purpose in mind. As it spins it tells you its current angle and the distance to the environment in the direction it’s pointing. They’re often used in robot vacuums to map walls and other obstacles. One night in 2021 I put it on the end of a stick and carried it around with my laptop recording timestamped measurements from it. By putting each scan sweep on its own layer I could make visualizations like this: Taken outside my apartment at the time during heavy snowfall. You can see the path cut through the snow on the sidewalk, the apartment building wall, windows, cars along the sidewalk, and points on a tree. Walking along the perimeter wall outside New Lab. Just behind the character is scaffolding. There are rectangles from windows. And if I remember rig...