德国铁路公司将试用无人机监控涂鸦行为

德国铁路公司计划于近期在各铁路站点区域试飞配备了红外相机的无人机，用以监控各区内公物在夜间被涂鸦或损毁的情况，并收集相关证据以便对破坏者进行处罚。不过，德国相当严苛的反监控法或对此类无人机的使用产生影响。德国铁路发言人表示，无人机上只会在夜间在车厢上涂鸦现象比较集中的大型站点上空飞行，红外相机也只关注铁路公司旗下的产业，铁路站点以外的人和物不在拍摄范围内。据悉，德国铁路公司每年用于清理各类涂鸦的花费高达760万欧元（约合100万美元），而每架无人机的成本约为6万欧元，可在距离地面150米的上空近乎无声飞行。

Germany's national railway company, Deutsche Bahn, plans to test small drones to try to reduce the amount of graffiti being sprayed on its property.

The idea is to use airborne infra-red cameras to collect evidence, which could then be used to prosecute vandals who deface property at night.

A company spokesman said drones would be tested at rail depots soon.

But it is not yet clear how Germany's strict anti-surveillance laws might affect their use.

Graffiti is reported to cost Deutsche Bahn about 7.6m euros ($10m) a year.

German media report that each drone will cost about 60,000 euros and fly almost silently, up to 150m (495ft) above ground.

Using cameras to film people surreptitiously is a sensitive issue in Germany, where privacy is very highly valued.

When Google sent its cameras through the country three years ago to build up its "Street View" of 20 cities, many people objected to their houses appearing online. Even Foreign Minister Guido Westerwelle said: "I will do all I can to prevent it".

Such was the opposition that Google was compelled to give people an opt-out. If householders indicated that they did not want their homes shown online, then the fronts of the buildings would be blurred. More than 200,000 householders said that they did want their homes blanked out on Street View.

A Deutsche Bahn spokesman told the BBC that its drones would be used in big depots where vandals enter at night and spray-paint carriages. The drones would have infra-red sensors sophisticated enough for people to be identified, providing key evidence for prosecutions.

But it seems the cameras would be tightly focused within Deutsche Bahn's own property - people or property outside the depots would not be filmed.

The drone issue is also sensitive in Germany because earlier this month the defense ministry halted an expensive project to develop Germany's own surveillance drone, called Euro Hawk.

The huge unmanned aircraft would be used abroad but would need to be able to fly in German airspace, if only to take off and land on their way to and from the land to be watched, our correspondent reports.

But it became clear that the air traffic authorities were not going to grant that permission. The reasoning was that Germany's military drones would be unable to avoid collisions with other, civilian aircraft.

Small drones on private land do not need permission from air traffic controllers - big drones do.

So Germany seems to be entering a legal grey area - it is not clear when the flight of a drone may become so extensive that the wider authorities need to intervene, Stephen Evans reports.