Haitians abroad relied on reports from their relatives on the web
Minutes after the earthquake, as phone lines collapsed, Haitians tried to discover the fate of relatives and friends by using the web and social networks.
"I don't know how, but most of the network infrastructure survived," said Reynold Guerrier, a network engineer at the Haitian Association for the Development of Information and Communication Technology (AHTIC).
Mr Guerrier said they still needed diesel to run their data centre, and he has been using the web to ask aid organisations for help.
But as many were e-mailing, Twittering and checking Facebook, thousands of volunteers joined forces to build a tool to help those in need - a combination of web and mobile phone technologies, traditional media and the voices of people on the ground.
maps reports sent by people in Haiti.
They can use mobile phones and the web to inform about structural risks, lack of water and food, and missing persons.
"We translate it, map it, and structure the data," said Ushahidi co-founder Erik Hersman.
"Then we pass it on to organisations on the ground which can then work with the specific needs reported by the people."
HOW THE MAP WORKS
People in Haiti can send their message to text number 4636 or through the website
The message is translated and formatted by a volunteer
The volunteer asks for more information and verifies it
The report is mapped
Aid agencies can take this message directly and act on it
Ushahidi made an agreement with local mobile phone operator Digicel and created a short code to which people could text their message.
That message is received by "situation rooms" set up in Boston and Washington. A third one will be set up in Geneva to provide 24-hour cover.
About 10,000 Haitians have volunteered to translate messages from Creole to English and ask for more information if needed.
Other volunteers and experts try to verify the information and put it into the map. This is crowdsourcing on a big scale.
Patrick Meier, director of crisis mapping at Ushahidi, told the BBC: "We had a Skype chat between a volunteer here in Boston and someone on the tarmac of Port-au-Prince airport asking for GPS co-ordinates for the most obscure addresses."
But how do you get Haitians who don't have access to the web to know about the map? By the most traditional media: radio.
Ushahidi worked with InSTEDD, an organisation that helps humanitarian collaboration through technology innovation. They visited local radio stations and tried to get the word around that Haitians could use the text short code 4636 to send their reports.
This is not the first crisis in which Ushahidi has operated.
The first map was created in the violent aftermath of the Kenyan elections in 2007.
"We saw that it worked and thought that, if it worked in Africa, it would work elsewhere," said Mr Hersman.
On the field
Haitians can report on the lack of water
Organisations in the field can use the information and redirect help to those in need. Internet access, though, is an obstacle.
"We are collaborating with the map and making sure that the information is correct," said Karina Brisby, head of digital campaigns at Oxfam.
"But the lack of good internet access hasn't allowed us access to the map, so we are relying on more traditional forms of information like the UN cluster system and satellite phones. The map supplements that information."
She believes that because internet access is not widespread in Haiti, many rely on their mobile phones.
She thinks this is why mobile phones are crucial during a crisis and why some organisations worked around the clock to set up new mobile phone masts as soon as possible.
"We wouldn't get any help"
Joel Dresse was in the US when the earthquake struck and travelled back to Haiti to rejoin his family and children.
He says he got the news from friends and relatives who were in Haiti by looking at Facebook, but added: "Internet access is getting sporadic now. I will probably have to go to the Dominican Republic border to buy some diesel for our generator."
For the few who can use the web, social networks did become a good way to communicate.
Yael Talleyrand, a 16-year-old in Jacmel, Haiti, said she used Twitter to "reassure people that some buildings were still up or that their family was okay".
"Also, no-one thought Jacmel was hit and if we didn't do something for people to know, we simply wouldn't get any help at all," she added.