Troubleshooting elevation results

This page helps users and developers interpret common issues: mismatched elevations, unknown datums, rate limits, and API errors.

1) “The elevation changed when I turned on more providers”

• By default, the app uses the same-origin API as the baseline.
• When you enable Run all third-party providers, you’re adding best-effort cross-checks.
• Those sources can disagree due to DEM resolution and vertical reference differences.

2) “Validation says CHECK / providers disagree”

3) “Units are confusing (meters vs feet)”

• Use the Toggle units button to switch display units.
• The API returns both valueMeters and valueFeet when available.

4) “Vertical reference says UNKNOWN”

• This usually means the upstream service did not declare a vertical datum/geoid in a way we can reliably parse.
• It does not mean the elevation is unusable — it means the vertical reference is not guaranteed.
• See: Vertical datum guide

5) “I got rate limited / blocked”

• Keep third-party providers off unless needed (they are rate-limited and sometimes block browsers).
• The same-origin API includes caching and basic rate limiting to reduce upstream load.
• If you need high-volume sampling, use raster catalogs + a server-side sampler.

6) “The map loads but elevation calls fail (CORS / Failed to fetch)”

• Try the same-origin endpoint first: it avoids browser CORS issues.
• Some networks block certain public APIs. Try another provider or test from a different network.
• Open your browser DevTools → Network tab → inspect the failed request.

Debug links

• API health
  /elevation/api/elevation.php?health=1
  Shows enabled providers, CORS policy, and security headers.
• Sample + debug
  /elevation/api/elevation.php?lat=29.0283&lon=-81.3031&debug=1
  Includes cache hints and (when enabled) post-processing diagnostics.