Show HN: Every mountain, building and tree shadow mapped for any date and time

Original Article ↗ Hacker News Discussion ↗

A web app that visualizes shadows from terrain, buildings, and trees for any place, date, and time is drawing praise for its usefulness in planning everything from solar panel placement and photography to home buying and parking. Users find the interface fast and insightful but note that accuracy varies widely by location, depending on data sources like OpenStreetMap and LiDAR, with missing or outdated trees, simplified building heights, and uneven coverage in rural or less-mapped regions. Many see strong potential for real estate, solar, and navigation use cases, while calling for clearer accuracy indicators and better ways to trial the premium data.

Overall Reception

  • Many commenters find the tool impressive, fast, and visually striking, calling it useful, even “sublime” and “moving.”
  • Others emphasize that it’s an approximation and warn against over‑trusting it, especially in poorly mapped areas.

Practical Use Cases

  • Planning shade/sun:
    • Where to park cars to stay cool in summer.
    • Picking shaded or sunny walking routes (summer vs winter).
    • Choosing stadium seats, lunch spots, or park benches.
  • Real estate and home use:
    • Evaluating sun exposure for house hunting and rentals.
    • Showing how new high‑rises block sun for existing homes.
    • Placing gardens, planter beds, and outdoor spaces.
  • Solar and energy:
    • Rough estimation of solar panel viability and shading over seasons.
    • Interest in RV/boondocking solar generation planning.
  • Photography:
    • Planning light/shadow for outdoor shots and “Manhattanhenge”-style events.

Accuracy, Coverage, and Data Quality

  • Mixed reports:
    • Some users see tree lines, forests, and building shadows matching reality very well, including historical vegetation.
    • Others report:
      • Missing large forests or most local trees.
      • Entire wooded areas or buildings absent or wrong.
      • Excessive shadows from small hills, or steep terrain timing errors.
  • “Every mountain, building and tree” is viewed as marketing overreach; many highlight incomplete coverage, especially outside well‑mapped regions.
  • Premium vs free:
    • Premium (about $2) reportedly adds more detailed tree and shadow data for some, but others still find inaccuracies.
    • Several want a way to trial full data on familiar locations before paying.
  • Data sources mentioned: OpenStreetMap (limited building heights), public LiDAR, “indirect” and crowdsourced sources; roof shapes are noted as missing.

Technical and UX Notes

  • Shadows from terrain work even where no buildings/trees are mapped.
  • Features praised: annual sunlight/hours-in-sun layers, ability to scrub date/time, canopy vs “below canopy” modes.
  • Issues raised:
    • Shadows vanish at lower zoom levels when buildings aren’t rendered.
    • DST handling looks confusing; local-time behavior is debated.
    • No visible “accuracy index” or data-age indicator by region.

Related Tools and Ideas

  • Several related apps and sites are mentioned for sun angles, shadow mapping, and solar planning.
  • Desired extensions include: shade-aware routing, perspective/visibility views, WISP/antenna planning, and crowd-sourced photogrammetry to refine heights.