推介:| 汽車配件 | 汽車維修 | 汽車雜誌 | 汽車保安 | 汽車音響 | 汽車代理 | 駕駛學院 | 汽車維修 | 洗車服務 | 電單車 | 二手車 |

發新話題
打印

香港都有用雷射鎗 型號: LTI20-20

香港都有用雷射鎗 型號: LTI20-20

9/12/2005
BBC Documents Errors in US Laser Speed Guns
British journalists test the American version of a popular laser speed gun and find it is inaccurate a third of the time.

LTI 20-20The BBC program "Inside Out" tonight will air results of tests of one of the most popular laser speed detection guns used by police forces in the US and UK. In the program, a pair of American specification LTI 20-20 guns, manufactured by Laser Technology Inc. of Colorado, point at the same moving vehicle but record substantially different speeds.

The source of the error is well-known. When the aiming point of the laser gun, which is designed to be hand-held, moves or "slips" across the target vehicle, an extra distance is either added to or subtracted from the speed calculation. A tiny movement can add up to a substantial difference. Engineering Professor John Brignell describes the amount of motion needed to cause a slip error at a distance of 500 meters: "Very roughly, without doing any calculations, we are talking about the camera moving about the thickness of a human hair."

The hosts of the BBC program were able to clock a stationary car at 6 MPH. In tests of a moving vehicle, the laser gun produced erroneous readings almost a third of the time, displaying speeds that were off by as much as 26 MPH.

The devices can be upgraded and used as mobile speed cameras, particularly in the UK where an estimated five million drivers have been convicted based on laser speed readings over the past five years.

"I am 100 percent certain that these devices are not suitable for gathering legal evidence of vehicle speeds," said Paul Smith, founder of the Safe Speed road safety campaign. "They make mistakes and the BBC film proves it. Millions of drivers will be entitled to refunds, licence points removed and in some cases a large amount of compensation."





Professor John Brignell

[ 本帖最後由 WURTH 於 2007-6-6 15:08 編輯 ]

TOP

MA 929/2000

Speeding/Reliability of laser gun/Certificate prima facie evidence of
regularity/Acceptance of expert evidence/ Relevance of possible margin of
error
超速駕駛 - 雷射槍的可靠程度 - 證明書是證明操作正常的表面證據 - 接納專家證據 - 可
能出現的誤差幅度是相關考慮因素

The Appellant appealed against his conviction on a fixed penalty
summons. The information showed that he drove a private car registration No.
HH 3XX6, on a road at a speed exceeding 50 kilometres per hour, being the speed
limit in force on that road, namely, at a speed of 65 kilometres per hour. That was
an offence contrary to s 41(1)(a) of the Road Traffic Ordinance, Cap 374.

There was no dispute that the Appellant was driving the car on the road
in question at the material time, nor that he was intercepted and given a fixed
penalty notice. The only issue before the magistrate was whether he drove at a
speed exceeding the speed limit and he noted that the burden rested on the
prosecution to prove beyond reasonable doubt that the Appellant did drive at a
speed exceeding 50 kmh.
The chief attack on appeal was as to the reliability and accuracy of the
laser speed detection system, that being LT 120-20 (serial no. 7859), which was
the equipment used by the police officer, PW2, to detect the speed of the car.
An independent expert, an Associate Professor of HKUST, was called by the
prosecution to give evidence about tests and examinations he had carried out on
the laser gun in question and on other laser guns of the same model and to give
his opinion on the accuracy and reliability of the laser gun.
Having admitted the witness as an expert, the magistrate concluded that
the laser gun was reliable and accurate when used on normal vehicles on the
road without flat or reflective surfaces. He also found that the laser gun
functioned as it was required to and that it could measure speed accurately
within the specified error margin.
He was satisfied that apart from the general accuracy of the laser gun
technique, the particular gun was working accurately at the material time when
the Appellant’s vehicle was shot by the gun. He was satisfied as well that the
laser gun operator was both a competent operator and a credible witness.
The magistrate also admitted into evidence a certificate under s 28 of the
Evidence Ordinance, Cap 8, which stated that on 24 January 1998 and 1 August
1998, namely, before and after the date of the offence, the manufacturer checked
the laser gun, found it was functioning properly and that the test results were
accurate. The contents of such a certificate stood as prima facie evidence of the
matters contained therein.

On appeal
Held :
(1) Having heard the expert’s evidence, the magistrate concluded that the
laser gun, radar and VASCAR systems were all accurate reliable speed detectors;
(2) The magistrate considered the expert evidence and concluded that at its
highest it could be said that the laser gun might be subject to interference by a
mobile telephone, but in that case the laser gun would produce an error message,
namely, no reading at all, rather than a wrong reading. The evidence at trial
showed that when the gun was shot at the Appellant’s vehicle, no error
message had appeared on the screen of the laser gun and there was no evidence
to suggest that the laser gun was subjected to interference at the time the speed
of the Appellant’s car was detected;
(3) The magistrate considered the curriculum vitae of the expert and
assessed his knowledge and admitted him as an expert for designing tests on the
laser gun and for commenting on its accuracy and reliability. He specifically
found that he was an independent witness, unrelated to the vendor of the laser
gun. It was for the magistrate to decide whether or not to accept the witness as
an expert;
(4) On the evidence the magistrate was satisfied that the operator of the laser
gun, who had attended a training course and regularly used it, was experienced
in using the gun. There was nothing to show that his finding was in any way
unreasonable, and an appellate court was not in a position to interfere;
(5) In HKSAR v Sham Wai-man, Walker MA 373/99, it was held that the
prosecution could rely on a certificate produced under s 28 of the Evidence
Ordinance, Cap 8. The magistrate found that the certificate was prima facie
evidence of the facts stated in it, and that the defence had not, on the balance of
probability, established that the contents of the certificate were inaccurate. He
accordingly drew the inference that the laser gun was operating normally
between the two dates of inspection in the certificate;
(6) The magistrate noted that for the purposes of this offence he had only to
be satisfied that the Appellant was exceeding the speed limit by 1 kilometre an
hour. He also noted that the Appellant had exceeded the speed limit by 19 kmh,
and he heard cogent evidence about the accuracy and reliability of the laser gun.
For the offence not to have been committed, the margin of error would need to
be at least 19 kilometres. That was relevant: Penny v Nicholas [1950] 2 All ER 89
followed;
(7) The magistrate dealt with the case correctly. He assessed the accuracy of
the laser gun procedure and was satisfied on that matter. He satisfied himself as
to the competence of the laser gun operator. He concluded that the Appellant
was guilty of speeding.
Result – Appeal dismissed.


相關搜索目錄: Driving

TOP

香港法官對用緊既雷射鎗係深信不移.  

TOP

香港代理:

美國雷射技術公司Laser Technology, Inc., 近年開發了一種新產品 LTI20 - 20 (UltraLyte)歐測利型手提鐳射測速器,在國際市場上已成功取代了雷達測速儀。由於雷達測速,主要是利用電磁波反射原理,易受外來因素干擾,且射 出微波角度寬,準確度大受影響,加上要用人手安裝固定才能操作,不夠快捷。對此,該公司研製出更先進、準確、輕便的手提鐳射測速儀,於1992年已開始批 量生產,並在美國正式啟用至現在,己獲很多先進國家和地區,包括美國,德國,英國,澳洲,澳地利,加拿大,瑞典,瑞士,荷蘭,中國廣東、香港、澳門和臺灣 等國家和地區認可採用。此外,LTI20-20型也經常被用於太空梭的機艙收放衛星任務中。
    此系統乃利用鐳射在極短時間內,作多次脈衝測距,通過獲接納之距離變化資料換算出速度,精確度為±2公里/小時。對小型汽車有效量程由10米至400米左 右,此系統本身之軟體己提供對被測目標之準確度及可靠性,如所獲資料不穩定或不合理,儀器將不會輸出結果而顯Er(「錯誤」


http://www.best-eng.com/lti/ultralyte.htm

理論:
http://www.best-eng.com/lti/laserandlider.htm

[ 本帖最後由 WURTH 於 2007-6-6 15:55 編輯 ]


相關搜索目錄: 汽車

TOP

TOP

發新話題


重要聲明:本討論區是以即時上載留言的方式運作,本網站對所有留言的真實性、完整性及立場等,不負任何法律責任。而一切留言之言論只代表留言者個人意見,並非本網站之立場,用戶不應信賴內容,並應自行判斷內容之真實性。於有關情形下,用戶應尋求專業意見(如涉及醫療、法律或投資等問題)。由於本討論區受到「即時上載留言」運作方式所規限,故不能完全監察所有留言,若讀者發現有留言出現問題,請聯絡我們。本討論區有權刪除任何留言及拒絕任何人士上載留言,同時亦有不刪除留言的權利。切勿撰寫粗言穢語、誹謗、渲染色情暴力或人身攻擊的言論,敬請自律。本網站保留一切法律權利。


Copyright 1997- Xocat. All Right Reserved.