With paragliding, sometimes we fly around airspace that goes from the surface up, sometimes we may carefully fly right over it if we have enough height to safely glide across, and sometimes we fly underneath it.
In previous posts I've referenced the USA Airspace file at soaringdata.info. This is a very comprehensive file and useful to save as a Google Earth folder that you can toggle on an off as required.
Unfortunately, this file is made of simple polygons. In some cases, the airspace that extends from the surface is 'clamped to ground' in Google Earth terminology. This makes it confusing and hard to understand if the airspace does not extend from the surface. You have to do some mental gymnastics to try and figure out where can fly relative to the airspace. It is more an abstract mental exercise that a pure visualization one.
For instance, in San Diego our Little Black flying site is right under airspace that goes from 3000ft to 10,000ft. A short distance away to the north, the airspace steps up to 3800ft. Then to the east, it steps up to 4800ft. If you are going to fly cross country from this site, you have to be careful not to thermal up into the airspace directly over launch where it is lowest, and then if the day is good, it is useful to know when you get another 1800 ft to play with as soon as you turn east wards.
Close to the popular XC route from this site, there is also a Class D airspace that goes from the surface to 3800ft. I'm not aware ever get high enough to fly right over this airspace, but the border of it is important, as it is close to hills that might be tempting to ridge soar low down in order to find thermals to continue and XC flight.
Example of simple 2-D airspace with flight from Little Black
Tracklog: Chris Cote
Tracklog: Chris Cote
In the example above from local San Diego guru Chris Cote, the flight starts under airspace, then you can see the pilot go towards the Ramona airspace (teal coloured circle at left, then change course to avoid the airspace and follow the sun and clouds.
For airspace that extends from the surface, Google Earth makes it quite easy to adjust an existing polygon to become a 3-D polygon that is much easier to visualize.
1. Click on the polygon from the airspace file in Google Earth.
2. Right click 'Properties'
3. Modify the Atitude to 'Relative to Ground' rather than 'Clamped to Ground'
4. Enter the altitude at the top of the airspace. In this case it is 1158m or 3800ft
5. Set the 'Colour and Area' settings to 50% opacity for both the line and the area, so you can see through it. Make the 'Color' setting "Outlined and Filled"
This results in a very nice 3-D polygon that is much easier to visualize.
For airspace that starts above ground, the 2D file is not easy to modify. It's easier to find a different Google earth file that was created from the start as 3-D airspace. This file shows US Airspace in 3D. Unfortunately this file doesn't have the Class D (the Ramona airspace modified above), so that was added in as a separate item in Google Earth.
The 3-D airspace give a much better appreciation of how thermalling up under stepped airspace can get quite complicated.You can see the grey semi-transparent blocks above the flying site, and the tracklog going close to the 3000 ft ceiling on the original climb. This airspace is so complicated due to the very large military airport at Miramar, and busy commercial airport in San Diego.
3D Airspace in Grey
Tracklog: Chris Cote
Thermalling out from Little Black under stepped airspace
Tracklog: Chris Cote
