Are the default airports accurate ?

[Guest]

Hi everyone. I

[Guest]

I have found oddities in placement myself, nothing is entirely precise with this business.Years ago Justin Tyme came to the conclusion that he needed to rotate each UTM zone by nearly 3 degrees/doqq with west of the zonal c/l rotating clockwise and east of zonal c/l rotating ccw. That was back when we were doing large areas of terrain mesh design for fs98.since then I'm doing airports, and the easiest thing for me is to take the runway data from www.airnav.com as the baseline. Lay out my runway to match. Then compare the msoft default with mine. If they match or are close, then I'll use the msoft location because then AI and nav aids from the default will work best. Then if the photo doesn't line up, I just rotate it to fit.As long as you work on only one airport, this works great, but my newest project will be to produce imagry all the way between Harvey Field and Monroe's First Air Field. Guess what?, to fit the www.airnav.com runway data for both fields with one photo is impossible, I must break the photoimagry into two, and rotate them with respect to each other by about 3 degrees...hmmmmm.Bob B

[Guest]

That's interesting because I found that rotating my photo 5 deg instead of 8 produced the best results for lining up the outlining roads. (8 deg is my true mag deviation from north) If I do this though then my airports are about a 1/2 mile out of place. I could just get the airports in the right place and deal with the road anomalies later. If I do that though,I still have the problem of the one runway being off by almost 20 degrees. (it's not even close and surrounded by trees in real life) Cutting the photo is really out of the question for me since I'm not that artistically talented. I guess my question is how would I relocate incorrect airport (if that is indeed the best thing to do) and then there's all of the problems of all of the directory data being wrong. HeHe...this little project is really getting quite involved. I guess that the most frustrating thing is that it's really tough to find all of the "tutorial" information in one place. I try to pick up a piece here and there from threads but it would be nice if it was all in one spot....(now there's a project !!) Here's a screen shot of my dilema (if I've uploaded it right)The yellow lines are the default runways and the green are the actual ones. By the Way...Thanks for the reply. I wasn't sure if I would get one. And definatly wasn't expecting one so soon !!

[Guest]

look up the data for the runways at airnav...could be that msoft just made a big mistake on the one airport.B

[Guest bones]

The airports aren't accurate - although this may vary between the US and the rest of the world. It boils down to how much information MS used from the Jeppesen database.In the case of our local airport it looked accurate and checking the main runway it was spot on - but then placing buildings around using their known Lat/Long (I have that data ..) resulted in severe misplacement. A few more checks and I think I know what's happened.Major runways should be spot on as the data is from Jeppesen. Secondary runways MAY be accurate but as we don't know the cutoff point for the data (runway length below xxxx?). Smaller runways and taxiways/ramps are probably not exactly right.The two larger runways at my local airfield are both spot on. One is 6000ft and the other 4200ft. A third runway of 3000ft is a good 500ft east of where it should be. The taxiways and ramps are all accurate relative to the third runway - so these are all 500ft too far east too! It's a guess but I'm assuming that MS got the accurate runway data and plonked it on their screens - and then drew in the rest of the airfields from charts. I have very high scale charts of our local airport (guess where I work!) and the taxiway/ramp data is about right, say +/- 20ft, but this is poor compared with runways accurate to three decimal places of a second.Point to note. The data for taxiways/ramps may be far more accurate in the US than the rest of the world so the above may not apply. Worth checking!My own suggestion is to make your airports as accurate as you can (because precise data is to hand) and then try and fit the road mapping to the airport systems.It's all good fun though - and the results are worth the effort.

[Guest]

Thanks guys !! I appreciate the help and input. I just didn't know if this was a fairly common occurrence with smaller airports. Most of the scenery I've dabbled with has just been adding a taxiway here or a building there to an existing airport. Stuff like that. I've never tried to make scenery for a large area. I'm sure I'll be back again before it's all over. By the way....Slightly off subject but..I've been reading these forums (mostly the design ones) off and on for well over a year now and I must say that this is a great group of people here. Lot's of helpful people and I hardly ever see anyone belittled for asking questions that I'm sure are simple to a majority of the community (kind of like mine). After pondering about my airport placement for well over a week, I knew where I could write and get a friendly answer without feeling stupid. This is a great community and Kudos to all involved !!

[Guest]

Bones, just checked out your website....fantastic. Thank you!Bob B