KyFromAbove Elevation Explorer

<p>The Elevation Explorer is optimized for mobile devices and allows you to view and download the highest and lowest elevations (and the highest above-ground object) within a specified area in your browser window. A green bounding box is placed over the map to indicate the current calculated extent. Check the edges of the bounding box because the elevations might be on the edge.</p><p><strong>How to use this application</strong></p><ol><li>Zoom and pan the map to your area of interest. The current window extent is used as the bounding box.</li><li>Select the desired base map from the <strong>Map Layers </strong>menu. Phase 1 and Phase 2 surfaces have a swipe user interface to compare the DSM and DEM.</li><li>Select a surface to calculate elevation and, optionally, <strong>Height</strong> mode from the toolbar. Note: To use Height mode, select a DSM surface.</li><li>Click <strong>Go</strong> to query elevation within the view.</li><li>At zoom &lt; 15, pre-computed spot elevations are used. At zoom ≥ 15, the raster surfaces are queried directly.</li><li>Results are placed on the map and saved to browser storage, where you can download them using the buttons found in the application's <strong>Info</strong> section.</li></ol><p><img src='https://nyc3.digitaloceanspaces.com/ballard/dgi/kygeonet/elevation-explorer-legend.jpg' alt='Legend' width='291' height='242' /></p><figure><img src='https://nyc3.digitaloceanspaces.com/ballard/dgi/kygeonet/elevation-explorer-hi-lo.jpg' width='2982' height='1742' alt='Example application showing high/low elevations in the state.' /></figure><p><strong>Browser storage</strong></p><p>Results are saved to browser storage automatically. A GeoJSON will contain the extent of each query as a polygon feature and the elevation and height values as point features. The <strong>Clear</strong> button on the main page will hide stored features (refreshing the page will show them again). The <strong>Clear Storage</strong> button in the <strong>Info</strong> section will permanently remove all stored features.</p><p><strong>Spot elevations (Zoom &lt; 15)</strong></p><p>At lower zoom levels, pre-computed spot elevations are used instead of querying the raster directly. The highest and lowest elevation points have been evaluated in each 5K grid cell statewide (Phase 2 DEM only). <span style='box-sizing:border-box; margin:0; padding:0; text-align:left;'>Enable those via the&nbsp;<strong>Spot Elevations</strong>&nbsp;checkbox, and use the&nbsp;<strong>Grid Lines</strong>&nbsp;checkbox to enable</span> the 5K grid layer.<br /><br />All grid cells that intersect the view are included. Because partial grid cells at the edges are counted, the highest or lowest point may fall outside the visible extent. The green footprint shows the full area that was evaluated. If no grid cells intersect the view, the raster is queried directly as a fallback. If the visible area exceeds 5 square miles, spot elevations are used even at zoom 15 and above. Zoom to level 15 or closer and keep the view under 5 sq mi to use all surfaces, height mode, and direct raster queries.</p><p><strong>Height Mode</strong></p><p>When enabled on a DSM surface, height is calculated as DSM − DEM (digital surface model elevation minus the digital elevation model elevation), representing the tallest object above ground within the bounding box. Available at zoom 15 and above.</p><p><strong>Analysis notes</strong></p><p>Elevation queries return two values: maximum and minimum elevations in the search area. If values are duplicated, only the first occurrence is displayed and saved. For example, searching for elevations over open, flat water should return the first elevation encountered. The same applies to height mode. Triangulation artifacts may occur near the shore and banks of water bodies in the DSM.</p>