Distortion

[Rob Killins 897126]

I am working on a sectorfile, and I'm noticing that my defined circles (and polygons) for control zones, become distorted the further north they are placed. Circles become ovals stretched side to side. These same sized circles situated further south do not appear, (or if they are, they are unnoticeably) distorted.

 

I use a combination of GoogleEarth and GEPath to compile the circular co-ordinates for coding into the sector file. The circles are pure on Google Earth.

 

Is there solution to overcoming the northernly distortion without manually editing the co-ordinates without any tool?

[Todor Atanasov 878664]

G can best answer this, but I remember there were similar issues with elements with North and South coordinates.

[Marvin Palmer]

Rob, I've pondered that as well, I trick I've just learned was to give the Latitude a lower number (i.e. N040.??.??.???) to design the object, then manually change the coordinates after it has completed the conversion to (i.e N072). I worked the Alaska (PAZA) for Euroscope and I noticed the same thing and I've now started to go back a slowly change all the objects north of the 65 Latitude line

 

Earth's curve vs. Flat map...

[Luca Benelli]

Shouldn't this be taken care by the program by setting the right values in the INFO section of the sct?

 

[iNFO]

Italy ES package v1.10e

LIUP_CTR

LIRF

N043.00.00.000

E011.15.00.000

60

44

0

 

I know i used those values to convert to CAD formats so that you can work non distorted, same in the reconversion....

 

Luca

[Halldor Bui Jonsson]

I believe this is due to the fact that the map projection is not circular but "stretched flat". Try defining .dcenter somewhere close to your circle and you will see it will unskew, however, circles farther south will then get messed up.

 

Hopefully one day we can have spherical map projection that will alleviate this problem for users not near the equator.

[Gergely Csernak]

Unfortunately the projection conversion in ES is far too simple. I calculate the size of one minute latitude and longitude at the center of your sectorfile and use a simple linear transformation based on that data. Changing the .dcenter really helps for that specific area but could make others worse.

[Jean-Frederik Dion 819740]

Modifying your own data just for the display is a very bad idea.

[Karl Sawatzky]

To revive an old post...

 

Has there been any further development on this, Gergely Csernák?

 

I'm not so much concerned with the circles but rather with the curvature of the earth.

 

Believe it or not, years later, I'm actually working on the same sector file that Mr. Rob Killins worked on back in the day.

 

Since we are dealing with a sector north of the 49th parallel, lines can get skewed very quickly, especially over large distance. For example, I'm trying to draw a specific line that stretches over 1200 nm in the north. Because of the curve of the earth, the line should actually appear as a slow arc between two points on a flat map, such as Euroscope.

 

Without adding many small way points along the way to FORCE a large curved line, is there any way of implementing the curvature of the earth into Euroscope so that these long lines, especially in the north, would appear correctly?

 

Thanks for your help!

[Gergely Csernak]

Just small steps ...

I have already changed all the internal code to work on the ellipsoid and not on the projected coordinates. At least the heading and distance calculations are far better now. The lines are still straight lines, but it is clearly visible that the heading vectors are a bit off even at our latitude on longer lines.