Updated documentation for isochrone smoothing (#472)

CHANGELOG.md

@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ### Added
 - Makes docker and docker-compose deployment of openrouteservice more customizable (Issue #434)
 ### Fixed
+- Updated documentation to reflect correct isochrone smoothing algorithm (Issue #471)
 - Enable > 2 waypoints when geometry_simplify=true (#457)
 ### Changed
 - Updated pom to always build ors.war (Issue #432)

openrouteservice/src/main/java/heigit/ors/api/requests/isochrones/IsochronesRequest.java

@@ -146,13 +146,14 @@ public class IsochronesRequest {
     private boolean hasInterval = false;
 
     @ApiModelProperty(name = PARAM_SMOOTHING,
-            value = "Applies a level of generalisation to the isochrone polygons generated as a `smoothing_factor` between `0` and `1.0`.\n" +
+            value = "Applies a level of generalisation to the isochrone polygons generated as a `smoothing_factor` between `0` and `100.0`.\n" +
                     "Generalisation is produced by determining a maximum length of a connecting line between two points found on the outside of a containing polygon.\n" +
                     "If the distance is larger than a threshold value, the line between the two points is removed and a smaller connecting line between other points is used.\n" +
-                    "The threshold value is determined as `(smoothing_factor * maximum_radius_of_isochrone) / 10`.\n" +
-                    "Therefore, a value closer to 1 will result in a more generalised shape.\n" +
+                    "Note that the minimum length of this connecting line is ~1333m, and so when the `smoothing_factor` results in a distance smaller than this, the minimum value is used.\n" +
+                    "The threshold value is determined as `(maximum_radius_of_isochrone / 100) * smoothing_factor`.\n" +
+                    "Therefore, a value closer to 100 will result in a more generalised shape.\n" +
                     "The polygon generation algorithm is based on Duckham and al. (2008) `\"Efficient generation of simple polygons for characterizing the shape of a set of points in the plane.\"`",
-            example = "0.25")
+            example = "25")
     @JsonProperty(value = PARAM_SMOOTHING)
     private Double smoothing;
     @JsonIgnore