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locationtech · Jun 14, 2017 · ac9fa3f · ac9fa3f
1 parent 65d154e
commit ac9fa3f
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Showing 2 changed files with 23 additions and 7 deletions.
diff --git a/raster/src/main/scala/geotrellis/raster/viewshed/ApproxViewshed.scala b/raster/src/main/scala/geotrellis/raster/viewshed/ApproxViewshed.scala
@@ -20,8 +20,16 @@ import geotrellis.raster._
 import spire.syntax.cfor._
 
 /**
- * Created by jchien on 4/30/14.
- */
+  * Created by jchien on 4/30/14.
+  *
+  * This appears to be an implementation of the DEM/Xdraw Viewshed
+  * algorithm from [1].
+  *
+  * 1. Franklin, Wm Randolph, and Clark Ray.
+  *    "Higher isn’t necessarily better: Visibility algorithms and experiments."
+  *     Advances in GIS research: sixth international symposium on spatial data handling. Vol. 2.
+  *     Taylor & Francis Edinburgh, 1994.
+  */
 object ApproxViewshed extends Serializable {
 
   def apply(r: Tile, col: Int, row: Int): Tile = {
@@ -49,7 +57,7 @@ object ApproxViewshed extends Serializable {
 
             if (layer == 1) {
               tile.setDouble(x,y,z)
-            }else {
+            } else {
               val xVal = math.abs(1.0 / (startRow - y)) * (startCol - x) + x
               val xInt = xVal.toInt
 
@@ -87,7 +95,7 @@ object ApproxViewshed extends Serializable {
               val closestHeight = {
                 if (startCol == x) {
                   tile.getDouble(x - math.signum(x - startCol), y)
-                }else if (yVal.isValidInt) {
+                } else if (yVal.isValidInt) {
                   tile.getDouble(x - math.signum(x - startCol), yInt)
                 } else { // need linear interpolation
                   (yInt + 1 - yVal) *  tile.getDouble(x - math.signum(x-startCol), yInt) +
@@ -101,7 +109,7 @@ object ApproxViewshed extends Serializable {
                 )
               } else {
                 tile.setDouble(x, y,
-                  math.max(z, -1.0 / (startCol - (x+1)) * (k-closestHeight) + closestHeight)
+                  math.max(z, -1.0 / (startCol - (x+1)) * (k - closestHeight) + closestHeight)
                 )
               }
             }

diff --git a/raster/src/main/scala/geotrellis/raster/viewshed/Viewshed.scala b/raster/src/main/scala/geotrellis/raster/viewshed/Viewshed.scala
@@ -20,8 +20,16 @@ import geotrellis.raster._
 import spire.syntax.cfor._
 
 /**
- * Created by jchien on 4/24/14.
- */
+  * Created by jchien on 4/24/14.
+  *
+  * This appears to be an implementation of the R3 Viewshed algorithm
+  * from [1].
+  *
+  * 1. Franklin, Wm Randolph, and Clark Ray.
+  *    "Higher isn’t necessarily better: Visibility algorithms and experiments."
+  *     Advances in GIS research: sixth international symposium on spatial data handling. Vol. 2.
+  *     Taylor & Francis Edinburgh, 1994.
+  */
 object Viewshed extends Serializable {
   def apply(r: Tile, startCol: Int, startRow: Int): Tile = {
     val (cols, rows) = r.dimensions