A path will be a series Hermite-Spline Curves. The Path is made up of series of Knot Points, Control Points, Control Weights, and Properties. These values will be generated and maintained by the PathBuilder utility program. The initial generation will be from the DRG maps of the railroad route. Each Knot Point may have properties of elevation, National Grid Location, the next Knot Point, Start, End, Map Source, Map XY etc. Any user path properties entered will generate a Knot Point. A Path may loop on itself. Any point on a Path is a unique distance from the Start property so that the same real world point may exist on the path more then once. Therefore, the same real world point maybe modeled on the path more then once. Real world National Grid Location and elevation are properties of a Knot Point. Lat/Long points in the model are an interpolation (approximation?) from the nearest Knot Point. The width of the path is a property inherited from the previous Knot Point. The width is also adjustable by the user from Knot Point to Knot Point. The width is perpendicular to the tangent of the path at the Knot Points. A property of the Knot Point is a rectangle that covers the beginning and end Knot Points widths both plus (North, East) and minus (South, West) of the path. The program will automatically adjust the path to meet main-line spiral or transition curves. The path may also be adjusted for smoothness. Terrain will be a property of the Knot Point rectangle. Billboard and billboard textures will be generated with the visible horizon lines from elevation data.

PathBuilder Workspace format extension .path

<?xml version="1.0" encoding="UTF-8"?> 
     <pathbuilder version="1.0" name="samuel" id="ffxffaab234aa"> 
          <catalogs> 
              <catalog name="catalog name" url="ftp://casil.ucdavis.edu"> 
                   <map name="some where" source="ftp://casil.ucdavis.edu" type="drg" 
                                                  upperleft="10sff0290948898" lowerright="10sff0290958898"> 
                      <file>file:///d:/maps/39121a1.tif</file> 
                      <file>file:///d:/maps/39121a1.tfw</file> 
                   </map> 
                   <map name="some where else" source="ftp://casil.ucdavis.edu" type="drg" 
                                                  upperleft="10sff0290948898" lowerright="10sff0290958898"> 
                      <file>file%3a///d%3a/maps/39121a1.bmp</file> 
                      <file>file%3a///d%3a/maps/39121a1.bpw</file> 
                   </map> 
              </catalog> 
              <catalog name="catalog name two" url="http://seamless.usgs.gov" > 
                   <map name="Donner Pass" source="seamless.usgs.gov" type="drg" 
                                                  upperleft="10sff0290948898" lowerright="10sff0290958898"> 
                      <file>file:///Z:/OSRailTestGIS/seamless/drg/00612248.zip#zip:00612248.tif</file> 
                      <file>file:///Z:/OSRailTestGIS/seamless/drg/00612248.zip#zip:00612248.tfw</file> 
                  </map> 
             </catalog> 
        </catalogs> 
        <paths> 
        </paths> 
     </pathbuilder> 
 

• catalogs - list of map sources
• catalog - a group of map sources, one of ftp, dav, dvd, cd, or local hard drive.
• map - a single map and other files, user supplied name location:
  • name user supplied name.
  • type one of:
    • drg
    • ned
    • doqq
    • nlcd
    • image
  • upperleft hex Location string.
  • lowerright hex Location string.

    The map must not cross the 100k boundary of the national grid hex string location, because the location interleave may not be a ring above that point(untested). An image is along the path so that it has only start and stop along the x or y national grid, not both. A map source is not the map location. If the map is on a local drive then its location is shown in the file element. Maps that are on the localhost can be found at the source by any computer that does not generate the same id attribute as in the pathbuilder element. DVD and CD maps will show a source of localhost in the map element and the local cd drive in the file element. If the id attribute is the same as localhost then the map can be found on the local cd drive.