Tunnel Extrapolation

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Revision as of 23:42, 9 July 2011 by Antenna (talk | contribs) (how to use)
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description

Tunnel extrapolation is an extrapolation function which calculates with the last available speed information once the gps signal is lost and if a tunnel flag is set within your openstreetmaps map.

how to use

To use tunnel extrapolation you need to patch navit/navit/maptool/osm.c by copying the three highlighted lines at the right place:

	  if (! strcmp(k,"hazmat")) {
	   	 flags[access_value(v)] |= AF_DANGEROUS_GOODS;
		 level=5;
 	  }
          if (! strcmp(k,"tunnel") && ! strcmp(v,"1")) {
                  flags[0] |= AF_UNDERGROUND;
          }
	  if (! strcmp(k,"note"))
		  level=5;
	  if (! strcmp(k,"name")) {
		  attr_strings_save(attr_string_label, v); 
		  level=5;

navit/navit/track.c needs to be edited too:

         if (!vehicle_get_attr(tr->vehicle, attr_position_valid, &valid, NULL))
             valid.u.num=attr_position_valid_valid;
  #if 0
         if (valid.u.num == attr_position_valid_invalid) {
             tr->valid=valid.u.num;
         return 0;
         }
 #endif
         if (!vehicle_get_attr(tr->vehicle, attr_position_speed, &speed_attr, NULL) ||


Also, you need to add "tunnel_extrapolation="12"" to <tracking ...>. You may need to lower this value, if the cursor runs ahead your position or vice versa, if it lags behind you. 12 stands for 1.2s extrapolation per gps rate.

Note, that this will only work if you processed your own maps with maptool and the tunnel is yet flagged in openstreetmap as well (it's not? Well, go ahead!)! This article is going to help you to get your own map: http://wiki.navit-project.org/index.php/OpenStreetMap#From_.bz2


This feature will be added to svn if it has been tested with success.