A discovery of conversions

[dritterb]

Tim, I found something which might help with the meridian situation.  Consider a plan comprised simply of PLPA to PLPA .  When saving in FSX format, the first coordinates convert properly, however the second conversion (of the same coordinates) is incorrect.  The airport is on a 000 meridian somewhere.  Since the data being converted is identical, yet the results are different, I feel the problem arises due to something left over from the first conversion, like maybe a sign bit or a remnant value or ???.  Does this make sense to you?  Is there anything I can do to help.  This is such a terrific program I want it to be a great success.

[tim arnot]

Is there anything I can do to help.

Find me a day job that pays lots of money yet leaves me free to work on P-G...  ;)

[dritterb]

Tim, are you ready for a little fun, a problem description and some solutions?  Follow this.  After installing Plan-G 2.0.5 I found a flightplan on the internet called "Iceland.plg".  Wow, Nice tour.  I'll bet you had fun creating it.  I got on my magic carpet and went for a ride.  The magic carpet's GPS took me from airport to airport.  Near BISI, the GPS took me way, way, way off course.  Bad, Bad Magic Carpet.  Bad, Bad GPS.  Bad, Bad Flightplan.  I rolled up my carpet and retreated to a private island in the Pacific.  I just happened to pick one with my hometown's name, Palmyra aka PLPA.  I started retraining MC for touch and goes when GPS informed me that there were two PLPA's.  And worse, the second PLPA was way, way, wrong.

Back to earth.  Tim, I realized there was a serious problem when, in the short time I've used Plan-G, there were two badly corrupted airport locations.   And they were repeatable.

The search started and I found a round up error.  It is causing FSX locations to appear in error, on the equator in the case of the latitude and the meridian in the case of the longitude.  The reason is clear and I can explain completely.  Instead of a lot more words, I will point directly at a problem and you can see it too.  BISI displays the problem, so does PLPA.  Now,specific example airport BISI. 

Ver 2.0.3.486 software generates a FSX flightplan file and notepad inspection shows the longitude coordinates are w18* 54' 59.999964".  This will be located properly in FSX. 

Ver 2.0.5.493 generates a FSX flightplan and the longitude coordinates are truncated to two places.  The truncation causes rounding.   Now the coordinates are w18* 54' 60.00".  FSX tolerates 55' 00.00" but not 54' 60.00".

Experimenting has verified that anytime the seconds value is 60.00, FSX discards the latitude/longitude (minutes) and displays the airport on/near the equator/meridian.

Solutions? Two suggestions. 
1) No truncation and avoid the rounding. 
2) When the flight plan is generated, a quick test for each waypoint/airport/POI etc.  If seconds=60.00 then seconds =59.99.  A slight loss in accuracy, but what is the length of .01 seconds?  a couple of centimeters?

[tim arnot]

Thanks, the 60.00 rounding error is a known issue. :)