[mapguide][MG104][New] distance measure incorrect in mapviewerjava sample

[Derrick Oswald]

You can view the artifact detail at the following URL:

    https://mapguide.osgeo.org/servlets/Scarab/id/MG104

Type
 Defect

Artifact ID
 MG104 (distance measure incorrect in mapviewerjava sample)

Reported by
 Derrick Oswald
 derrickoswald (Derrick.Oswald at Autodesk.com)

New artifact details:
---------------------------------------------------------

- Priority set to new value
  P4
- Component set to new value
  All
- Summary set to new value
  distance measure incorrect in mapviewerjava sample
- Subcomponent set to new value
  N/A
- Operating system set to new value
  All
- Platform set to new value
  PC
- Version set to new value
  1.0.0
- Artifact Status set to new value
  New
- Description set to new value
  The formula used for distance measure in measure.jsp from the mapviewerjava sample seems to have a couple of problems.

The first is that the X values are used for latitude and the Y values for longitude. A typical value for the Sheboygan area is X = -87.717882 and Y = 43.727963. It would seem that the Y value is latitude and the X value longitude.

The second is that the formula provided computes a distance of near zero unless there is a difference in X (longitude).


- Defect Severity set to new value
  Low
- Steps to Reproduce set to new value
  A better computation, garnered from http://www.movable-type.co.uk/scripts/LatLong.html, is:

            //Calculate the distance
            //
            double radlon1 = Math.PI * x1 / 180;
            double radlon2 = Math.PI * x2 / 180;
            double radlat1 = Math.PI * y1 / 180;
            double radlat2 = Math.PI * y2 / 180;
            double deltalat = radlat2 - radlat1;
            double deltalon = radlon2 - radlon1;
            double sinlat2 = Math.sin (deltalat / 2);
            double sinlon2 = Math.sin (deltalon / 2);
            distance = sinlat2 * sinlat2 + Math.cos (radlat1) * Math.cos (radlat2) * sinlon2 * sinlon2;
            distance = Math.abs (distance);
            distance = 2 * Math.atan2 (Math.sqrt (distance), Math.sqrt (1 - distance));
            distance *= 6371;
            if(0 != us)
                distance /= 1.609344;  //convert to miles
            total += distance;

- Artifact created

---------------------------------------------------------
This message was automatically generated by Project Tracker.