Ask HN: What is the most impactful thing you've built?

I guess my most impactful project was a microprocessor-based weather station for siting wind energy systems and fruit frost prediction in the early 1980s. Turned out that one of my stations, being used by a frost predictor, was across the street from a rural drainage ditch in which a young child was discovered face down in the water. The frost predictor faxed temperature profiles for the previous several hours to the hospital, where doctors determined the child could be revived. She was.

I started an airplane turbulence forecasting website for nervous travelers back in 2005 (think - will it be bumpy when I take my flight from Chicago to New York tomorrow?). It started by repackaging government turbulence maps in an easy to use manner, and has evolved into a service where I handwrite forecasts of turbulence for your flight, and now offering automated turbulence forecasts.

It has been used by employees at nearly every airline, including dispatchers, flight attendants, captains, and I've gotten many emails saying it has allowed people to fly again, to take new jobs, and continue relationships because they know what to expect when they fly.

Site: www.turbulenceforecast.com

I was nominally the lead engineer on the first release of AdWords, though most of the actual code was written by Jeremy Chau. AdWords pretty much changed the world, though not, I think, for the better. :-(

If you want to know what I actually made by myself that I'm most proud of it would be this: https://graceofgodmovie.com/ (I am referring to the movie, not the web site.)

I created http://tetration.org which explores what lies beyond exponentiation. My life's work has been to extend the Ackermann function to the complex numbers and matrices. I believe my website lead to a renaissance in tetration research. The following Mathematica code replaces a thousand lines of earlier code. It computes the flows from maps. Combined with the historic three argument Ackermann function it allows the Ackermann function to the extended to the complex numbers.

order=10;

H[0]=0;

H[1]=f'[0]^t ;

Do[H[max]=First[r[t]/.RSolve[{r[0]==0,r[t]==Sum[Derivative[k][f][0]BellY[max,k,Table[H[j]/.t->t-1,{j,max}]],{k,2,max}]+ f'[0] r[t-1]},r[t],t]],{max,2,order}];

Schroeder=f'[0]^t z+Sum[1/k! H[k]z^k,{k,2,order}]

Abel=Limit[Schroeder,{f'[0]->1}]

I wrote a vaccine booking availability scraper that helped double digits of people get a COVID vaccine a few weeks sooner otherwise.

A temporary low resource form for people in Puerto Rico to send an SMS message out to family outside of PR after Hurricane Maria.

During Hurricane Maria most of Puerto Rico was offline. Slowly but surely, some people started having access to some online services. To this day, I don't know how, but I saw frequent posts in social media (Facebook and others) of people saying they could access spotty internet but SMS and making calls wasn't working, and asking people to let their family outside of Puerto Rico know that they were okay.

So I setup a site on glitch.com with real simple 2 field form. One for a phone number and another for a message to send. It was dead simple, no framework, no CSS, just little bits of vanilla HTML and JS, and a bit of backend code connected to Twilio. Some text on the top with instructions too. I was making it intentionally small so that a spotty connection wouldn't have a problem using it.

Any time I saw someone posting in social media asking for someone to reach out to their family, I posted a link. I also shared it in a slack where many from the PR diaspora where trying to contribute ways to help. Before I knew thousands of people were using it. I did some continuous monitoring to make sure nobody was using it for abuse, and making sure it was being used as intended. It would have been EXTREMELY easy for someone to abuse it if they wanted to.

No one abused it. Thousands used it as it was intended. Left it up for weeks, and I kept monitoring it to make sure it wasn't being abused. I eventually saw it had stopped being used entirely for two weeks and spun it down.

I saw some people posting about it afterwards being thankful they were able to receive messages from their family, and I'm happy I rushed through to write very sloppy high impact code.

Monodevelop, I think: https://www.monodevelop.com

It wasn't a planned thing. I had recently got injured playing football, so I was stuck at home, not being able to walk or drive. I started checking the #mono IRC channel (it was 2003 and internet was something you did over a 48k modem, when your home phone line was not needed). Some guys, lead by Miguel de Icaza, the founder of Gnome, were implementing a compiler of C# and a bytecode interpreter of .NET IL, and I was very curious about it. I kept downloading, compiling and trying things out.

Then one day Miguel wrote in the channel that it would be nice to have some graphical editor and that somebody could perhaps port SharpDevelop over to Linux, by replacing Windows.Forms by calls to GTK. I said that I'd give it a shot and... well, 10 days later we had a working editor and half a dozen of contributors.

https://tirania.org/blog/archive/2008/Mar-14.html

A long time ago I worked for one of the big medical journal publishing firms. (No, the other one.) I was one of the lead software developers, nominally in charge of the web application that served all of our licensed content to medical professionals and librarians all over the world. I was senior enough at that point that I attended regular planning meetings with the CEO and her team.

We were working on a new product, electronic access to textbooks. I'd built the entire system that takes the textbook XML we got from the content side, created indexes used by our search engine, and made it possible to efficiently display in the web application any text fragment from a full chapter down to a single sentence containing a search result.

The CEO called an emergency meeting: many of our library customers were government funded, and their funding required the library to receive a physical object in exchange for the licensing fee. They didn't want to have to store the physical textbooks and we didn't want the overhead of sending them textbooks. So the team starting talking about creating an entire new subdivision dedicated to the production, management, warehousing, and shipping of CD versions of the books, just so the customers could be given something physical.

I interjected: "If a CD is good enough, I can generate that using everything I've built already. I'm already converting the content to HTML for display in the app, so I can render the textbook out to a folder, one HTML page per chapter, with a table of contents and all of the images, and create an ISO image that the librarians can download using a link in the web application. Let them burn it themselves if they want a physical copy. They could also store the ISO locally so they still have that version if they let their license expire." That was a funding requirement as well.

So that's what we did. It took me a couple of days extra to implement that feature, and I saved the company a fortune compared to what they were considering doing.

I believe I got a $25 Starbucks card as a reward.

For 10 years until recently a statistics research system that was the primary tool for keeping granular measurements on the health of the US economy.

I've worked on numerous medical devices, many startups. From treating cancer, kidney disease, or providing tools for reconstructive surgery.

Nothing hits you in the feels than having customers thanking you for improving their quality of life, or a child thanking you for giving a parent more years of life.

We are two friends working on a native app to analyze videos using computer-vision [0]. We have been developing it for more than 2 years, to make sure it works in real-time for all CPUs. Not sure about impact but it is really cool to play and analyze videos in real time and help unlock some of the values stored in lot of video libraries. [0] https://ramanlabs.in/static/videointel.html

A whole bunch of labor agreements that extended our operations over thousands of new route miles. Got pretty much had what both labor and management really needed, got ratified by membership, worked decently in the real world.

I used Microsoft Word.