[Serval]

If you contact me I can help work out some details of the airfields you mention.
I'll have to make some high quality scans and ask around and put the information on the FTP server.

About the symbols:
The first symbol means Demolished airfield. They simply plowed the field and destroyed everything else.
Like statedbefore, Harskamp and Oldebroek were no real airfields, but artillary areas where there was a landingstrip.
But also other airfields were harly more then a field.

Some links (don't hesitate to post there in English, there are quite a few with very good knowledge about may 1940 around there):
Airfield Ruigenhoek
http://www.nederlandseluchtvaart.nl/for ... meer-1839/
Ockenburg
http://www.nederlandseluchtvaart.nl/for ... 39-a-1219/
Screenshots of a FS add-on for Waalhaven
http://www.nederlandseluchtvaart.nl/for ... loot-2883/
Bergen
http://www.nederlandseluchtvaart.nl/for ... rgen-3742/
Ypenburg
http://www.nederlandseluchtvaart.nl/for ... 40-a-4516/
Waalhaven
http://www.nederlandseluchtvaart.nl/for ... haven-559/