Pictures on how to prevent men from looking up their skirts are posted on micro blog by Zhejiang provincial public security bureau.

Detailed instructions for women on how to prevent men from looking up their skirts have been making the rounds on China's Internet, sparking a heated debate.

Posted by the Zhejiang provincial public security bureau, the pictorial guide includes a geometric formula that calculates the posture, angle and distance at which a man could look up a woman's skirt when riding up an escalator or in other similar situations that provide opportunities for peeping.

Liu Zhongmin, spokesman for the Zhejiang provincial public security bureau, said a female colleague posted the information to their official micro blog as on Wednesday.

"We're not the original author of these pictures and formulas, but we browsed a great amount of related information to select what was most useful and did the editing. Look at this first picture. It was reported by a netizen," Liu said, referring to a photograph in which a man put his cell phone camera under the skirt of a woman at a bus stop.

"We receive lots of complaints about indecent acts toward women every year when the weather turns hot, and we felt the need to do something," he said.

Liu said locations like supermarkets, bus stops and escalators are places where women are vulnerable.

He suggested a few simple self-protection measures, such as wearing leggings underneath a skirt or pulling the shopping cart behind the back to prevent men from sneaking up from behind.

This update was widely forwarded, and the post was carried on the micro blogs of many police departments, including the public security offices in Chengdu, Wenzhou and Hangzhou.

"It's such a kind tip," said 27-year-old female Ma Xin who works at a State-owned enterprise in Tianjin. "But this tip also reflects our unsafe and unhealthy environment. They've (the police) got no option but to release such a notice because society is filled with creepy peeping Toms."

Shanghai office worker Dong Shuangyan, 28, said many people may lack the expertise in mathematics required to understand the illustrations.

"I don't understand these geometric formulas and functions at all, and in my opinion, men can see these pictures as well, so it could act as instructions for them to do creepy things, right?" said the young woman, who was wearing a short skirt.

"I had this kind of trouble with harassment as well, but my tip is to keep a cactus with you so that when a stranger touches you, you can hit them back. Another thing to remember is to keep your hip very close to the handrail of the escalator."

Dong Zhiqing from Chongqing Jiaotong University said the pictorial guide is indeed too mathematical for the masses to understand.

"The most important thing is in reality, nobody would actually calculate the distance and angle between the stranger and you," said Dong, adding that the illustration could only be used as a reference rather than an instruction.

Some netizens left comments disparaging the waste of police resources on what they consider petty things.

"I don't understand why the police have this much time and effort for things like this because you couldn't really convict somebody for peeping," said Xu Shuang, who works as the public relations manger at a five-star hotel in Beijing.

"They should promote information, such as encouraging women to get legal consultations when they are harassed at a public place, rather than wasting time trying to make the news."

But legal experts said self-protection is extremely important for women because obtaining evidence for a harassment case can be hard.

Zhou Dan from Shanghai Shaogang Law Firm said: "DNA identification can be used as evidence for rape charges because it usually lasts minutes, but sometimes peeping or harassment only lasts for a couple of seconds, and there's no evidence except your own observation."

"I'm with the police simply because it's easier to protect yourself than to pursue legal action afterward," said Zhou.