Ground control points for aerial survey

[RonaldWe]

Hi,

I like to do an aerial survey from about 100 to 200 m altitude and I am looking for a solution for the ground control points.

Ideally the points should have the following requirements:
- good visibility
- easy to transport
- light weight
- fixed to the ground (no flying away by wind)
- low cost
- if possible: decomposable, so I do not have to pick the points up after the survey 

Until now I used paper plates, but they are hard to fix to the ground and are prone to rain and hungry sheep.
Any recommendations?

[eriks]

white and/or black spray - water based so it will disappear after 3-4-5weeks.

[d.portillo@habitatea.es]

Paper archery target. I?ve two sizes 40*40cm and 20*20cm