include sidewalk width in calculation (and document it) (#4499)

* include sidewalk width in calculation (and document it) to address #4494 * intentionally reduce widths way below realistic estimates see #4494 (comment) * adjust values * adjust values * more adjustment Co-authored-by: Tobias Zwick <newton@westnordost.de>
streetcomplete · Oct 21, 2022 · d597473 · d597473
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diff --git a/app/src/main/java/de/westnordost/streetcomplete/osm/RoadWidth.kt b/app/src/main/java/de/westnordost/streetcomplete/osm/RoadWidth.kt
@@ -113,6 +113,7 @@ private fun estimateCyclewaysWidth(tags: Map<String, String>, isLane: Boolean):
     return leftWidth + rightWidth
 }
 
-private const val BROAD_LANE = 4f
-private const val LANE = 3f
+// rather under-estimate then over-estimate the road width
+private const val BROAD_LANE = 3.75f // standard interstate/motorway width
+private const val LANE = 2.75f // widest trucks are about 2.6m
 private const val SHOULDER = 2f
diff --git a/app/src/main/java/de/westnordost/streetcomplete/quests/sidewalk/AddSidewalk.kt b/app/src/main/java/de/westnordost/streetcomplete/quests/sidewalk/AddSidewalk.kt
@@ -42,7 +42,7 @@ class AddSidewalk : OsmElementQuestType<LeftAndRightSidewalk> {
         /* Unfortunately, the filter above is not enough. In OSM, sidewalks may be mapped as
          * separate ways as well and it is not guaranteed that in this case, sidewalk = separate
          * (or foot = use_sidepath) is always tagged on the main road then. So, all roads should
-         * be excluded whose center is within of ~15 meters of a footway, to be on the safe side. */
+         * be excluded whose center is within several meters of a footway, to be on the safe side. */
 
         if (roadsWithMissingSidewalks.isNotEmpty()) {
 
@@ -75,11 +75,14 @@ class AddSidewalk : OsmElementQuestType<LeftAndRightSidewalk> {
         return roadsWithMissingSidewalks + roadsWithInvalidSidewalkTags
     }
 
+    /* Calculate when footway is too far away from the road to be considered its sidewalk.
+       It is an estimate, and we deliberately err on the side of showing the quest too often. */
     private fun getMinDistanceToWays(tags: Map<String, String>): Float =
         (
             (estimateRoadwayWidth(tags) ?: guessRoadwayWidth(tags)) +
             (estimateParkingOffRoadWidth(tags) ?: 0f) +
-            (estimateCycleTrackWidth(tags) ?: 0f)
+            (estimateCycleTrackWidth(tags) ?: 0f) +
+            1.5f    // assumed sidewalk width
         ) / 2f +
         4f // + generous buffer for possible grass verge