Watch: 35,000? 55,000? Data scientist uses drone to estimate hīkoi crowd

A data scientist has used drone footage to calculate an estimate of how many people joined yesterday’s hīkoi, saying he believes at least 40,000 people took to the streets but that the actual number could be much higher.
Caleb Moses, who is studying in Canada, watched the protest from afar yesterday and said as a Māori man he was proud to see the turnout.
The former Stats NZ statistical analyst has qualifications in pure mathematics, has worked for Dragonfly Data Science and is currently doing a PhD in computer science focusing on AI (artificial intelligence) and language technology – especially for low-resource languages such as te reo Māori.
He used two separate methods to estimate the crowd size, with his first estimate coming to at least 83,000 people.
Moses believed his second estimate on crowd size might be more accurate, though he said it still didn’t account for people already at Parliament or those who showed up after the initial hīkoi.
“The first one was a traffic cam timelapse where the crowd was moving through Manners St,” he said.
He used a video editor to try to reverse the timelapse and estimate how long it took people to pass through the area and what the crowd density was.
He noted people had to pack tightly together to move through Manners St, and there was some uncertainty about the frame rate of the video, which he felt might throw the estimate off somewhat.
His second method involved having a friend, Greg Thomas, bring a drone and fly it over the length of the hīkoi. Moses then analysed the footage to determine the length of space taken up by protesters, drew the pattern on a map and calculated the estimated crowd density, along with the area of the march.
“We found the total space taken up by the party from Waitangi Park was about two hectares or 20,000 square metres,” he said.
Moses estimated a density of two people per square metre.
This calculation gave him an estimate of at least 40,000 people, but he believed it could be closer to 50,000 attending the protest in total when factoring in people arriving later or those who were at Parliament from the start.
He made that assumption based on an 80/20 model, guessing 80% of protesters were in the hīkoi group and 20% were not.
The adjusted 50,000 estimate was “still a lower bound”.
Either way, he believed the number was more than 40,000 “and probably by a lot”.
Moses described himself as “proud Ngāpuhi”.
“I’m very proud of what my people organised. It seems that the hīkoi went very well and was very successful. There wasn’t so much as a scrap of rubbish on the ground [afterwards].”
He said his auntie in Wainuiomata spent the evening after the protest providing massages for sore, tired whānau.
“It was a really great example of everyone coming together and showing some solidarity, and that people still care about the Treaty of Waitangi these days.”
Estimates about the hīkoi size have varied widely, ranging from about 20,000 to 100,000.
One official estimate widely used by media was provided by the police, who put out a statement yesterday giving a figure of 42,000.
The Herald asked the police how this number was reached, but the response did not provide hard methodology.
“Police use venue capacity planning figures to estimate crowd size and consider comparisons with known reference points from previous events,” a spokesman said. “We will also collaborate with partners to strengthen our numbers estimates.”
Melissa Nightingale is a Wellington-based reporter who covers crime, justice and news in the capital. She joined the Herald in 2016 and has worked as a journalist for 10 years.