I was poking around the forum trying to find the format required to enter lat long fixes in a flightplan, and what I found seems to be in error. All references I found indicate using decimal values to a maximum of 2 decimal places multiplied by 100, so the result is always an integer value. For example
123.54N,80.42W -> 12354N/8042W
I was getting results that were in error by ±20mi! I stumbled onto the fact that a much more accurate result was obtained by using degrees and minutes instead of decimal degrees! This is the format that resulted in very accurate results for me…,
DDMM(N/S)/DDDMM(E/W)
So if your fix is 34deg37minN by 90deg50minE, the value you use in IF IS…
The point of this post is to point out that using decimal degrees results in an error! If your fix is 34.50degN 90.30degE, don’t enter 3450N/9030E as that will give you a slight error. A more accurate result is to convert that to deg min and enter this value…
3430N/9018E
I discovered this when trying to create a FP that would line me up on a runway. I couldn’t do it if I used decimal degrees. After playing around with different formats I stumbled onto the fact that degrees minutes were much more accurate!
I love this finding, I’ve had a heck of a hard time using this feature myself despite the help of existing tutorials. I must say it doesn’t make sense though because decimals should resolve to 0.6nm while arc minutes a flat nautical mile. I believe you though. To date my success has come from simply scrolling the map to the approximate coordinate intersections, zooming in carefully and panning around looking to visually find a fix on the map, then copying the format to find the fix I need. This has only worked sometimes, and it doesn’t correspond to the format described in the tutorials. For example, 20N,141W is listed as “20N41”, still not clear on why. This format has not worked for other fixes I’ve tried to find.
Again, I appreciate your work @GHamsz, this is great but I’m still having a hard time, really want to get to the bottom of it, so here are two questions for you. First, if I go into the flight planning map and search for “3437N/9050E”, nothing comes up. What am I doing wrong? Were you actually able to find that exact fix or were you just creating a plausible example? Second, how does IF’s coding know whether you’re inputting decimals or arc minutes? Let’s just focus on the “3437N” component as an example. How does IF know to read this as 37 arc minutes, rather than “point three seven degrees”? In the case of say “3488” it would have to be decimal of course… But do you see what I’m saying? Not trying to tear this down because it sounds like you’re onto something, I’m just not convinced we know how to fully use this system yet.
1min is approximately 1nm. If the value you’re using is say 34.5, which is 34deg 30min, and you enter 3450 instead of 3430, you’ll be 20mi off!
Play around with the DDMM format and you’ll see it’s very accurate. I used the lat long of a few different airports to verify that DDMM did indeed work.
Oh ok I see that, thank you, you’re saying IF is built to understand arc minutes only, so any decimal coordinates need to be converted to degrees-minutes by multiplying the decimal by 60? That makes sense. Still can’t find the coordinates you listed by any format though.
Yes that’s great, I think a big advantage of this is for missing fixes- if you have a fix that isn’t available in IF you can just find the coordinates instead to keep your flight plan right on. Ok I’ll keep playing, I wish I knew what you’re doing that I can’t figure out though.
Sorry to carry on, but how would you input even degree coordinates, eg 37degrees00’? 3700N, or just 37N?
That makes sense, let me try that. I’m currently located at 33d37’N, 117d54’W, trying everything to make that work. I’ll punch in some fixes around KSNA to try to make it happen, will let you know. Thanks for following me down this rabbit hole, because 3337N/11754W doesn’t work for me right off, i’d love to make it work. Here’s a thought: do you know if the coding is supposed to literally be able to fix any geographic coordinate, or just a good series of them that are on established airways? Anyway I’ll let you know if I can find a way to make it work, maybe the problem is just me
HA! Thanks so much buddy, I get it now. I have been searching for a fix, adding it to the fpl, then searching for the next. The procedure is to input your whole fpl in that bar… OK! I’ll shut up now! Maybe everybody in the world has been doing it this way but me, but I’ve been inputting fixes separately for ages, and this is clearly the difference. Sorry to hijack your thread, but Infinite Thanks.
