[mkgmap-dev] Proposed change to splitter to make tile names unique

Sun May 20 17:44:36 BST 2018

Dear Sirs:

I propose adding the following to uk.me.parabola.splitter.AreaList.java:

*** AreaList-old.java    2019-05-20 11:28:45.739455200 -0500
--- AreaList.java    2018-05-11 20:01:47.861375200 -0500
***************
*** 280,286 ****
              cityFinder = new DefaultCityFinder(cities);
          }
          for (Area area : getAreas()) {
!             area.setName(description);
              if (cityFinder == null)
                  continue;

--- 280,286 ----
              cityFinder = new DefaultCityFinder(cities);
          }
          for (Area area : getAreas()) {
!             area.setName(description + "-" + openLocationCode(area));
              if (cityFinder == null)
                  continue;

***************
*** 350,354 ****
--- 350,401 ----
          }
      }

+     private static final String codes = "23456789CFGHJMPQRVWX";

+     private static String openLocationCode(Area area) {
+         return openLocationCode(
+                 Utils.toDegrees(area.getMinLat()),
+                 Utils.toDegrees(area.getMinLong()),
+                 Utils.toDegrees(area.getMaxLat()),
+                 Utils.toDegrees(area.getMaxLong()));
+     }
+    
+     private static String openLocationCode(
+             double south,double west,double north,double east) {
+         double centerLatitude = 0.5 *(south + north)+90.;
+         double centerLongitude = 0.5 * (west + east)+180.;
+         double boxHeight = north - south;
+         double boxWidth = east - west;
+         double height = 400.;
+         double width = 400.;
+         String code = "";
+         boolean done = false;
+         while(code.length() < 8  & !done) {
+             int p;
+             height /= 20.;
+             width /= 20.;
+             p = (int)Math.floor(centerLatitude/height);
+             code += codes.charAt(p);
+             centerLatitude -= p * height;
+             p = (int)Math.floor(centerLongitude/width);
+             code += codes.charAt(p);
+             centerLongitude -= p * width;
+             done = width <= boxWidth && height <= boxHeight;
+         }
+         if(!done) {
+             code += "+";
+             while(!done) {
+                 int la, lo;
+                 height /= 5.;
+                 width /= 4.;
+                 la = (int)Math.floor(centerLatitude/height);
+                 centerLatitude -= la * height;
+                 lo = (int)Math.floor(centerLongitude/width);
+                 centerLongitude -= lo * width;
+                 code += codes.charAt(5*la+lo);
+                 done = width <= boxWidth && height <= boxHeight;
+             }
+         }
+         return code;
+     }
  }

The purpose is to give each tile an unique name by appending the Open
Location Code of the largest region (shortest code) that fits within the
tile. I have been using this code myself.

https://en.wikipedia.org/wiki/Open_Location_Code

Randolph J. Herber

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