Three-dimensional laser scanner measures source of error and precision analysis

Foreword is three-dimensional laser scanning technology is the innovation of another mapping technology after technology of fixed position of afterwards GPS space, will make of mapping data get method of method, service ability and level, data processing to wait enter new development level [1] . Traditional earth measurement technique, be like triangulation method, GPS is measured is the measurement that is based on a dot, and three-dimensional laser scanning is to be based on the data of the face to collect means. The primitive data that three-dimensional laser scanning obtains is the data that nod the cloud. The data that nod the cloud is the foundation of all succeeding activity, in data the inevitably meeting in collecting a process contains an error, nod cloud data quality to rise, need undertakes detailed analysis to source of error. The person such as Wallace studied the deepness image of trigonometry laser scanner measures a principle 1997, pass experimental test and verify the systematization error that the shift of scanning object can cause deepness image to measure [2] . 2000 the person such as Wu Jianfeng labor laser is trigonometric the error of range finding [3] . 1.

Principle of work of system of scanning of the ground three-dimensional laser is three-dimensional to the ground for laser scanner, those who use is instrument coordinate system, the spatial information that the object surface that collects namely nods is with its the coordinate system of oneself is accurate. The system is coordinate origin with surging emissive point of beam of light; The vertical stroke that Z axis is located in an instrument to scanning face inside, it is up; X axis is located in inside the transverse scanning face of the instrument; Inside the transverse scanning face that Y axis is located in an instrument and as perpendicular as X axis, be like graph 1-1, the consideration that can get bit of coordinate from this is formulary: 2.

The source of error of the data that nod the cloud and analyse three-dimensional laser to measure an error to be able to divide for: The requirement of instrument error, outside ambient of sum of errors that concerns with face of target object reflex affects these 3 kinds. By (1) type is knowable, instrument error results from the function blemish of instrument itself, the error that includes laser range finding (the error of S) , the error that scanning angle measures (error) ; The error that with target object reflection face concerns basically is the influence of exterior surface roughness; Outside ambient condition basically includes the factor such as temperature, wind, atmospheric pressure. In popularly face environment of work of three-dimensional laser scanning falls, the error of the data nodding the cloud that we think three-dimensional laser scanning gets the area basically is cause by the error of scanner oneself [4] , so we are necessary to clear up the origin of the error. 2.

　 of 1 instrument error 2.

1.

Range finding of laser of error of 1 laser range finding handles each link to be able to bring certain error in signal [2] . The principle of laser range finding has two kinds now, pulse type and phasic type. The error that pulse range finding produces basically is timing error, the error that phasic law range finding produces basically is the frequency error of modulation light. In instrument use process, wait for a reason as a result of the ageing of electronic component, the standard frequency of actual modulation frequency and design can produce little difference, this influence and place range finding become direct ratio from length, say for " scale error " ; Additional, because calculate since distance of range finding system,the center finds a place for with its the center is abhorrent wait for a reason, make actual measurement distance and actual distance have a fixed margin, say for " fixed error " . To " fixed error " and " scale error " , can decide through instrument calibrating, can decide error of laser range finding thereby. Write down fixed error to be, scale error is, criterion is the range finding error that range finding length is: ? ? .

1.

The affects scanning part influence of 2 scanning horn includes the effect that horizontal scanning angle and upend scanning angle measure. What lens of the error of part of lens face plane that the error that scanning angle causes is scanning lens, scanning turns is tiny shake, the blame of scanning electric machinery turns equably the combined influence that commands the element such as the error. The error that measure part establishs a point to measuring influence formula is: Have: to three-dimensional laser scanner? ノ of  of Bo of Xi of  of ∈ market body shakes Mu of a round flat piece of jade with a hole in its center of  of bad Min of  of Yun of error of す of  of    to ask  ! ? .

1.

Influence of emanative of 3 laser velocity of light is in actual application, most scanner system is to use the time that is based on laser pulse to measure those who will undertake is apart from measuring. Because stimulate the character of disperse the internal heat with sudorifics of beam of light, make the uncertainty that the facula volume that stimulates beam of light to arrive at hypostatic surface is affecting the resolution that answers cloud ejaculation a point and fixed position [5] . Launch laser suppose diverge of Shu Chengyuan form, use finally to the facula of hypostatic surface express, next type hold water: The distance parameter that with laser light beam emissive position concerns is in type. Generally speaking, as scanning the distance increases and linear increases the size of facula. The linear equation that emanative facula size can be apart from by a scanning will express. A lot of instrument manufacturer demarcate the size that the facula diverge of respective system is worth, if the facula size of Trimble GX200 is 3mm/50m, lai blocks HDS3000 to be 6mm/50m. The distance of three-dimensional laser scanner measures the ground determine along the central line of emissive beam of light. Because the diverge of laser light beam makes,nod truly forecast hard [6] . Be in as a result of hypostatic scanning likewise before, hypostatic position and appearance also are sealed. Reason needs a reliable model to quantify the uncertainty level of beam of light. Set the diameter that stimulates beam of light to be, angle locates change is. Does the uncertainty that rolls out the width of beam of light that come by density formula convey following type: ? "  Ba Du truly artisan phlegmy male calls a courtyard to carry a surname on the back truly the character of? of Dao Jia of  of wood of  of  of my crusty pancake, by experience judgement is had, the positional uncertainty that stimulates beam of light approximates the diameter of facula of disperse the internal heat with sudorifics of 1/4. Like type: ? Does a surname of 〖 in the company of embed head of admonish of tiny stream Lin of alkyne skirt  relatively does D of copy of magpie of lament of razor clam fresh hole knock fade of dusk of travel of extensive of ㄎ of broadleaf plant of Mei of envy favor frequency to guide busy of extensive of travelling bag of oath collate dim glow of the setting sun looks collect of  of skirt of miscellaneous argon of provide for benzyl does commonplace of benzene of elder brother of cowardly of tiny stream carbonyl impossible archives? ? .

Closely related the crude rate of the nods the cloud precision that the 2 error scanning that concern with face of target object reflex get and object surface. The much value sex of signal of three-dimensional laser echo [7] , make the echo signal that system of different three-dimensional laser scanning processes different. In order to handle first echo signal is exemple, crude rate causes target object appearance the deviation of position of laser foot spot is adjacent at object surface the half of coarse extreme value. 2.

The influence outside ambient of condition of 3 outside ambient measures an instrument to be able to produce the effect of different level to everything, heat bilges cold shrink the change that can make instrument structure generation subtle, bigger wind- driven conference makes the instrument vibrates the influence scans quality. Poorer outside ambient condition is bigger to the influence of scanning data quality. The careful degree of the observation precision of three-dimensional laser scanner and scanning distance and scanning concerns the ground, be aimed at scanner of Trimble GX200 three-dimensional laser, through the experiment research discovery measures main source of error to scan at range finding sum of errors horny error. The range finding precision when scanning distance is 50m is 1~2mm, only place locates precision is 6mm. 3.

Three-dimensional laser scanner uses the last word extensively at each domains at present, it is the heat of research. The article basically studied three-dimensional laser measures source of error -- the effect of instrument error, outside ambient of sum of errors that concerns with face of target object reflex. The range finding precision that was informed instrument Trimble GX200 through the experiment and scanning precision. CNC Milling