Question: “Roughly how high is this location?” Good for: site familiarity, map notes, pre-visit planning.

1. Search an address/place or click the map.
2. Read the main elevation value (toggle meters/feet as needed).
3. Check Method / Dataset / Resolution in the Source panel.
4. If you need more confidence, enable one cross-check provider (not all).
5. Use Copy summary to paste into an email/ticket with provenance.

• Recommended sources: same-origin API baseline + (optional) EPQS cross-check in the U.S.
• Watch for: Unknown vertical reference. Use as best-available only.

Question: “Is this location plausibly below (or near) a flood/SLR threshold?” This is not a hydrodynamic model, but it helps with fast screening.

1. Sample your point of interest (POI).
2. Sample 4–8 nearby points (25–100 m around the POI) to understand micro-topography and DEM smoothing.
3. Check validation: if it says CHECK, treat the result as uncertain and investigate why.
4. Prefer higher-resolution/bare-earth sources when available.
5. Document the vertical reference expectations of your threshold (e.g., NAVD88 vs unknown).

• Recommended sources: USGS 3DEP-derived products when working in the U.S.; treat global DEMs cautiously for sub-meter decisions.
• Watch for: comparing a modeled water surface to elevations from a different datum/geoid.
• Tip: in very flat areas, small differences can come from interpolation, datum, or vegetation/buildings in a DSM.

Question: “Does this spot appear higher/lower than the surrounding area?” Useful for sanity checks and field interpretation.

1. Sample the point of interest.
2. Sample 8–12 points along likely flow paths (toward ditches, culverts, canals, shoreline).
3. Look at differences, not just absolute elevation.
4. If results are noisy, increase the spacing (e.g., 50–200 m) to reduce pixel-to-pixel jitter.

• Recommended sources: DTM/bare-earth DEMs where possible (LiDAR/3DEP), not DSM.
• Watch for: bridges and overpasses (some DEMs burn water/roads; others don’t).

Question: “How does elevation change along a line?” Elevation Explorer’s History sparkline is a quick visual for repeated samples.

1. Click points along your route/transect in order (start → end).
2. Use the Profile toggle in the History card to show the sparkline.
3. Export CSV for analysis in GIS, Python, or Excel.

• Recommended sources: stay on one dataset for the entire transect when possible (mixing sources can create artificial steps).
• Watch for: mismatched units or toggling providers mid-profile.

Question: “Why does my GNSS device/phone disagree with this app?”

1. Confirm your GNSS device output reference: orthometric height vs ellipsoidal height.
2. In the app, check Vertical reference and notes.
3. Compare multiple nearby points (GNSS positions drift; DEMs are gridded).
4. If the difference is large (many meters), suspect datum/geoid mismatch first.

• Recommended sources: use the datum guide to understand conversions; for deliverables, use surveyed control.

Goal: integrate elevation lookup into an app without fighting CORS or public rate limits.

• Prefer server-side calls (same-origin API) for reliability and consistent headers/caching.
• Batch and cache aggressively for bulk sampling (tiles/COGs when possible).
• Always store provenance: dataset name, resolution, vertical reference, timestamp.