Age-based opacity for heatmap

Author: zstadler

Styles/OSM_traces.json

@@ -19,7 +19,23 @@
       "paint": {
         "line-color": "yellow",
         "line-width": {"stops": [[8, 1], [10, 2.5]]},
-        "line-opacity": 0.6
+        "line-opacity": [
+          "interpolate",
+          ["linear"],
+          [
+            "-",
+            ["+", 2023, ["/", 5, 12]],
+            [
+              "+",
+              ["to-number", ["slice", ["get", "start_time"], 0, 4]],
+              ["/", ["to-number", ["slice", ["get", "start_time"], 5, 7]], 12]
+            ]
+          ],
+          0,
+          0.6,
+          3,
+          0.1
+        ]
       }
     },
     {
@@ -33,7 +49,23 @@
         "line-color": "rgba(0, 128, 0, 1)",
         "line-blur": 0,
         "line-width": {"stops": [[8, 0.2], [10, 1]]},
-        "line-opacity": 0.6
+        "line-opacity": [
+          "interpolate",
+          ["linear"],
+          [
+            "-",
+            ["+", 2023, ["/", 5, 12]],
+            [
+              "+",
+              ["to-number", ["slice", ["get", "start_time"], 0, 4]],
+              ["/", ["to-number", ["slice", ["get", "start_time"], 5, 7]], 12]
+            ]
+          ],
+          0,
+          0.6,
+          3,
+          0.1
+        ]
       }
     }
   ],