Watch Los Angeles get built, one building at a time (1880–2026)

Extends the existing LA building footprint visualization to include county‑wide data, surrounding municipalities, ocean/land differentiation, and demolished‑building layers so users can see the city as it truly evolved over time.
Core value proposition: an interactive, static‑site map that lets anyone explore Los Angeles’ growth, decline, and redevelopment patterns with clear geographic context and toggleable styles.

Key	Value
Target Audience	Urban planners, historians, real‑estate professionals, and curious residents of Southern California
Core Feature	Unified 3D/2D map of LA County (city + incorporated towns) showing building footprints, heights, year built, and demolition status; ocean/land basemap; light/dark mode; time‑slider to animate construction/demolition from 1880 to present
Tech Stack	DuckDB (spatial join of assessor rolls & demolition permits), Tippecanoe → PMTiles, MapLibre GL JS with fill‑extrusion & hillshade layers, static hosting on Cloudflare R2/Pages
Difficulty	Medium
Monetization	Hobby

HN users noted the map “makes it nearly impossible to tell the ocean and the land apart” (sgt) and wished for “more data for a complete picture of the area” (slg); this project directly addresses those comments.
Adding demolition data would answer ZeWaka’s concern that “the older periods look extremely empty” and rustywasm’s note that “what was torn down … isn’t here.” The resulting visualization could spark discussion about urban renewal, gentrification, and policy impacts.

Aggregates and normalizes building permit data (new construction, alterations, demolitions) from LA City/County APIs, providing per‑address timelines that show when a structure was built, modified, or removed.
Core value proposition: gives homeowners, researchers, and developers a clear, queryable history of any parcel’s evolution, enabling fact‑checking, investment analysis, and preservation research.

Key	Value
Target Audience	Homebuyers, real‑estate analysts, preservationists, journalists, GIS enthusiasts
Core Feature	Searchable address → interactive timeline (Gantt/map overlay) of permit events; ability to filter by permit type, view scanned documents, and export CSV/JSON; optional LLM‑based extraction for unstructured PDF permits
Tech Stack	Python/FastAPI backend, PostgreSQL + PostGIS for spatial data, Apache Airflow for periodic API pulls, LLM (e.g., Llama 3) for PDF parsing, React/TypeScript frontend with Chart.js or TimelineJS, deployed on Fly.io or Vercel
Difficulty	High
Monetization	Revenue-ready: Freemium (free basic lookups, paid API access & bulk exports)

Commenters like tcdent described extracting permits via LLMs and expressed interest in “incorporating more granularity of the history of properties over time”; PermitLens productizes that effort.
Providing permit‑based demolition data would satisfy rustywasm’s wish to show “what was torn down, burned, destroyed” and enable users to validate claims about lost neighborhoods (e.g., Venice canals, Palm‑era buildings).
The tool could become a go‑to resource for journalists and policy analysts studying housing supply and urban change.

Web tool that lets California homeowners input purchase year, original purchase price, current market value, and any exemptions to compute their effective property tax rate under Prop 13, compare it to a market‑based tax, and explore deferral or equity‑loan options to access trapped equity.
Core value proposition: demystifies the financial effects of Prop 13, highlights potential savings or costs from reform, and provides actionable pathways for homeowners to leverage their home equity without selling.

Key	Value
Target Audience	California homeowners, real‑estate advisors, financial planners, policy advocates
Core Feature	Input form → instant tax‑burden comparison, visual chart of tax paid vs. market tax over time, scenario sliders for Prop 13 reform (e.g., reassessment on sale, adjustable rate), integrated links to state postponement programs and HELOC calculators
Tech Stack	SvelteKit frontend, Node.js API, optional Firebase Firestore for saved scenarios, hosted on Netlify/Vercel
Difficulty	Low
Monetization	Hobby (could add premium “tax‑planning report” upsell)

The discussion thread is filled with Prop 13 critiques (e.g., “Prop 13 massively distorts the real estate market” – tikhonj) and mentions of postponement programs; this calculator directly addresses those pain points.
By giving users concrete numbers, the tool can fuel informed debates in comment sections and help individuals decide whether to pursue property‑tax deferral, sell, or leverage equity—topics that generated strong engagement.

🚀 Project Ideas