CN106952297A - A kind of laser scanning data point cloud degree compression method - Google Patents

A kind of laser scanning data point cloud degree compression method Download PDF

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Publication number
CN106952297A
CN106952297A CN201710173764.4A CN201710173764A CN106952297A CN 106952297 A CN106952297 A CN 106952297A CN 201710173764 A CN201710173764 A CN 201710173764A CN 106952297 A CN106952297 A CN 106952297A
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point
data
cloud
compression
point cloud
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罗欣
王蓉
陈红艳
吴宝峰
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University of Electronic Science and Technology of China
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    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T9/00Image coding
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00Indexing scheme for image analysis or image enhancement
    • G06T2207/10Image acquisition modality
    • G06T2207/10028Range image; Depth image; 3D point clouds

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Abstract

A kind of laser scanning data point cloud degree compression method of the invention, belongs to Point Cloud Data from Three Dimension Laser Scanning compression method, and cloud data compression is implemented in combination with point-connectivity theory in graph theory.This compression method is applicable not only to dispersion point cloud, is equally applicable to the orderly point cloud of distribution rule;Single site point cloud before registration is applicable not only to, multi-site point cloud after registration is equally applicable to.Four functions of this method can be used alone, and can also repeat and mutually undertaking is used, directive property compression is with conspicuous characteristics.It as open cloud data compressed platform, can continue to extend other compression functions, it is adaptable to the cloud data compression of different geometric shapes and compression purpose, expand space larger.

Description

A kind of laser scanning data point cloud degree compression method
Technical field
The invention belongs to Point Cloud Data from Three Dimension Laser Scanning compression method, it is implemented in combination with a little with point-connectivity theory in graph theory Cloud data compression.
Technical background
With the sustainable development of three-dimensional laser scanning technique and being substantially improved for scanning device precision, the distribution of Bian sampling points is more Crypto set is with accurately, and obtained point cloud quantity can be quite huge, also just inevitably generates mass of redundancy data point.These Redundant digit strong point brings inconvenience to the further application of the cloud data in later stage, and takes big quantity space in the data transmission And resource, reduce these redundant points imperative.In addition, the target compressed sometimes is not necessarily redundant points cloud, for non-superfluous Remaining cloud, according to later stage application target difference, it is necessary to be compressed to significant initial cloud data, reservation presumptive area, Predetermined point is studied.Such compression algorithm only one of which purpose, meets the different compression requirement of user to greatest extent.
The content of the invention
The present invention proposes the stronger point cloud degree compression method of practicality.This compression method is applicable not only to dispersion point cloud, It is equally applicable to the orderly point cloud of distribution rule;Single site point cloud before registration is applicable not only to, multistation after registration is equally applicable to Point point cloud.Four functions of this method be can be used alone, and can also repeat and mutually undertaking is used, and directive property compression feature is dashed forward Go out.As open cloud data compressed platform, can continue to extend other compression functions, it is adaptable to different geometric shapes and The cloud data compression of purpose is compressed, is expanded space larger.
The yulan tree scattered point cloud data chosen herein for the three observation station for acquiring in ground carries out registration and obtains original Cloud data is illustrated.It is first according to each point digital complex demodulation in data (the z values in three-dimensional coordinate) from low to high Order carries out lossless arrangement again;Then carried out according to the point cloud of rearrangement according to user's request piecemeal, in each cloud mass A virtual point is inside obtained respectively, and the coordinate of this virtual point is exactly the average value of each point coordinates in block, then obtained respectively in block Distance of each point to this block virtual point;Finally sorted from small to large again in each piece according to this distance value.Two minor sorts Sequence number allows for each point and imparts new coordinate, the lookup and deletion that can be pinpointed according to this sequence number.
Technical solution of the present invention is a kind of laser scanning data point cloud degree compression method, and this method includes:
Step 1:Vegetation cloud data is obtained from different orientation by multiple websites, then by the cloud data of each website It is unified to arrive under same coordinate system, realize the registration of each website cloud data;
Step 2:First according to x in three-dimensional coordinate, y, z is worth size to formulate data point sort method, will own in step 1 Data point is ranked up according to the sort method of formulation, obtains sequence cloud data collection N;
Step 3:Required according to compression, the suitable point cloud number n of selection carries out piecemeal, the row for obtaining step 2 in units of n Sequence cloud data collection N, carries out piecemeal in order, and that is finally discontented with n data point is individually for one piece;
Step 4:The mean point V of all data points in each piece is calculated first0, each data point is calculated in block to mean point V0Distance and angle, each data point in block is ranked up again further according to distance, each point sequence sequence number is obtained;
Step 5:By each point sequence sequence number in block and the point to mean point V0Distance and angle set up corresponding relation, from And each piece obtains one by sequence number, the corresponding distance of each sequence number and angle, this block mean point V0The packet of composition, realizes number According to compression.
Further, the specific method of the step 1 is:From a point converge P in choose a number of data point, and The corresponding data point of these points is searched out in consecutive points converge Q;Then, by least square method iteration, optimal seat is calculated Transformation parameter is marked, even if error function:In R and t it is minimum, wherein R is spin moment Battle array, t is translation vector, and n is the sum for the data point chosen, qkK-th of data point in Q, p are converged for the point of selectionkTo choose Point converge k-th of data point in P;By the smart registration result at preceding two station by identical step and the 3rd adjacent site cloud data Registration is carried out, comprehensive complete individual plant vegetation cloud data can be finally obtained.
Point cloud degree compression method is applicable not only to dispersion point cloud compression, is also applied for orderly point cloud compression;It is applicable not only to match somebody with somebody Single site point cloud compression, is equally applicable to multi-site point cloud compression after registration before accurate.Point cloud degree compression method can just be realized multiple Function, and replace other a variety of compression methods, user will be not used in wasting twists and turns on selection compression method, repeat alternately or Undertaking can just complete the effect that other compression methods reach using difference in functionality.
Brief description of the drawings
Fig. 1 is yulan tree original point cloud data schematic diagram;
Fig. 2 is a cloud degree structural representation;
Fig. 3 is leaf original point cloud data schematic diagram;
Fig. 4 is schematic diagram data after the compression of 30 points of execution distal end;
Fig. 5 is schematic diagram data after the 40 points of compressions of execution near-end;
Fig. 6 pinpoints schematic diagram data after 49.9% compression to perform;
Fig. 7 is present invention point cloud degrees of data compression method flow chart.
Specific implementation step
1) data acquisition:
In order to obtain complete vegetation cloud data, it is necessary to be scanned from different azimuth to vegetation, and by will be adjacent Target in website cloud data carries out pressure as control point and met, and can complete the rough registration to multistation cloud data, i.e., Point cloud under different coordinates is substantially unified under the same coordinate system.Then, by smart registration, it can make between multi-site cloud Stitching error reaches minimum.If P, Q converge for the point of the same object in different station for acquiring, and point p, q are measured object body surface Conformation of the face any point in different coordinates point converges, i.e. p (xp,yp,zp) ∈ P, q (xq,yq,zq) ∈ Q, cloud data Smart registration seeks to make the point of two points any expression body surface same point in converging to (p, q), meets identical conversion, I.e.:
Wherein, R is spin matrix, and t is translation vector.The present invention use ICP algorithm (iterative closet point algorithm, Iterative Closest Point), it has main steps that:First, it is assumed that an initial position and state estimation, i.e., from Point converges and chosen in P a number of point, and searches out in consecutive points converge Q the corresponding points of these points;Then, minimum is passed through Square law iteration, calculates optimal coordinate conversion parameter, even if error function
Minimum R and t.The registration process of two station vegetation cloud datas is as shown in Figure 2.The smart registration result at preceding two station is pressed Identical step is registering with the 3rd site cloud data progress, can finally obtain comprehensive complete individual plant vegetation cloud data.
2) point cloud arrangement:
The object of scanner scanning any shape, the data of acquisition are all the cloud data collection of a limited range, are obtained Individual plant yulan tree point cloud chart picture such as Fig. 1.Because the arrangement of these cloud data collection is unordered, study for convenience, by this A little point clouds re-start once lossless arrangement according to the orders of DEM (the z values in three-dimensional coordinate) from low to high.Point cloud after arrangement Rearranged according to new sequence number, this sequence number is just to confer to the repositioning information of dispersion point cloud.With z values from low to high In alignment processes, if there is z value identical situations, just compare x values, x values are larger to be arranged in front, it is less be arranged in after, If x values are still identical, continue to compare y values, y values are larger to be arranged in front, it is less be listed in after.
3) cloud piecemeal is put:
The cloud data collection N rearranged, requires that the suitable point cloud number n of selection carries out piecemeal, with n according to the compression of user Started counting up for unit from DEM minimum values, full n restarts next count and circulated.Unit often comprising a n cloud we regard For one piece, the unit of a remaining discontented n clouds is individually considered as one piece, and whole point cloud thus is divided into M blocks.It is expressed as:
M=int (N/n)+1 (3)
4) arranged again in block:
To the x of an every piece of n clouds (last block is less than n), y, z averages respectively:
According to Dist values, (each point is apart from block center virtual point V0Distance value) n point in block is carried out again once from It is small to arrive big lossless arrangement.V0With being formed after n line as shown in Fig. 2 V in figure0Point is just V in n degree point, virtual point cloud mass0 Point cloud degree (point cloud degree) just be n.Virtual point V0Connect remaining each point to greatest extent in figure, and answering Play a part of control in, associate remaining each real point.Monoblock point cloud is constituted after point cloud degree network, it is meant that huge three-dimensional Each point (being n point in each block altogether) in each block of scattered point cloud data can be with virtual center point V0Between all can There is the relation of a distance, be also n distance value of correspondence altogether so between minimum distance to maximum distance, so that In per module unit, with virtual point V0The n that is connected clouds have been assigned the location information from 1 to n, at this moment from 1 to any of n One numeral and V0Number combine just represent a point, just can more facilitate to enter any block point cloud by such method Row two-dimensional digitalization is retrieved, and is that next step compression lays the foundation.
5) method is realized:
Monoblock point cloud constitute point cloud degree network after, it is meant that huge unorganized point cloud repartitioned into by V0The two-dimensional coordinate system that number is constituted with n values.And in every module unit, with virtual point V0The n that is connected clouds have been assigned from 1 arrives n location information, at this moment any one numeral and V from 1 to n0Number combine just represent a point, by such Method just can more facilitate carries out two-dimensional digital retrieval to any block point cloud, is that next step compression lays the foundation.
Below by taking the cloud data (4583 points) of yulan tree leaf as an example, such as Fig. 3.Each function is presented in order to protrude Effect, the point cloud of leaf is divided into 46 pieces by us according to every piece of 100 points here.
A. remote point compresses
According to user's needs, to V0Remote point is compressed, and this function has denoising, deburring, integer for cloud data Function.Such as Fig. 4, when reducing 30 of distal end, the noise of blade distal end is deleted, and the peripheral shape of blade is closer In actual blade.
B. proximal points are compressed
For V0The compression of proximal points, this function has for cloud data to be put cloud, extracts point cloud framework in sparse piece Function, perspectiveization is had more in the case where profile is integrally constant.Such as Fig. 5, when the proximal points of compression are, blade is being kept at 40 On the premise of profile, the translucency of blade interior is more obvious, and perspectiveization is protruded.
C. interval point compresses
Needed to set respective bins according to user, and the point cloud in interval is compressed.With the pressure to designated area Contracting function, compression possesses certain directive property.
D. specified point compresses
It is compressed, is reduce to the unwanted specified point of user for specified point in cloud data, directive property is more dashed forward Go out, compression effectiveness is obvious.The function is enough when cloud data piecemeal, such as carries out 2292 pieces of divisions to 4583 points of point cloud, often Block only has at 2 points, when a point to every piece carries out specified point compression, rate 49.9891% is exactly compressed to a cloud and is compressed, Because in 2 points of adjoint points each other in upper piece, the global feature after compression will not be lost, and compression efficiency is high.Such as Fig. 6.
This 4 kinds of functions can carry out repeatedly or accept according to different requirements to compress to same data, to reach expection Effect.Because destroying the quantity of original point cloud and being distributed limited and process control, compression process belongs to Lossless Compression.Point Cloud degree compression method flow is as shown in Figure 7.Algorithm is realized using Windows7, VS2010 platform herein, C++ application programs Exploitation is completed, auxiliary Geomagic Studio 12 complete point cloud and shown.

Claims (2)

1. a kind of laser scanning data point cloud degree compression method, this method includes:
Step 1:Vegetation cloud data is obtained from different orientation by multiple websites, it is then that the cloud data of each website is unified To under same coordinate system, the registration of each website cloud data is realized;
Step 2:First according to x in three-dimensional coordinate, y, z is worth size to formulate data point sort method, by all data in step 1 Point is ranked up according to the sort method of formulation, obtains sequence cloud data collection N;
Step 3:Required according to compression, the suitable point cloud number n of selection carries out piecemeal, the sequence point for obtaining step 2 in units of n Cloud data set N, carries out piecemeal in order, and that is finally discontented with n data point is individually for one piece;
Step 4:The mean point V of all data points in each piece is calculated first0, each data point is calculated in block to mean point V0's Distance and angle, are ranked up to each data point in block again further according to distance, obtain each point sequence sequence number;
Step 5:By each point sequence sequence number in block and the point to mean point V0Distance and angle set up corresponding relation so that respectively Block obtains one by sequence number, the corresponding distance of each sequence number and angle, this block mean point V0The packet of composition, realizes data pressure Contracting.
2. a kind of laser scanning data point cloud degree compression method as claimed in claim 1, it is characterised in that the step 1 Specific method be:From a point converge P in choose a number of data point, and search out these in consecutive points converge Q The corresponding data point of point;Then, by least square method iteration, optimal coordinate conversion parameter is calculated, even if error function:In R and t it is minimum, wherein R is spin matrix, and t is translation vector, and n is the number chosen The sum at strong point, qkK-th of data point in Q, p are converged for the point of selectionkK-th of data point in P is converged for the point of selection;Will The smart registration result at preceding two station is registering with the 3rd adjacent site cloud data progress by identical step, can finally obtain comprehensive Complete individual plant vegetation cloud data.
CN201710173764.4A 2017-03-22 2017-03-22 A kind of laser scanning data point cloud degree compression method Pending CN106952297A (en)

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WO2019210531A1 (en) * 2018-05-03 2019-11-07 北京大学深圳研究生院 Point cloud attribute compression method based on deleting 0 elements in quantisation matrix
CN111598803A (en) * 2020-05-12 2020-08-28 武汉慧点云图信息技术有限公司 Point cloud filtering method based on variable resolution voxel grid and sparse convolution
WO2021248339A1 (en) * 2020-06-09 2021-12-16 深圳市大疆创新科技有限公司 Point cloud encoding/decoding method and apparatus
US11535400B2 (en) * 2020-05-09 2022-12-27 Nanjing University Of Aeronautics And Astronautics Fairing skin repair method based on measured wing data

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2019210531A1 (en) * 2018-05-03 2019-11-07 北京大学深圳研究生院 Point cloud attribute compression method based on deleting 0 elements in quantisation matrix
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US11535400B2 (en) * 2020-05-09 2022-12-27 Nanjing University Of Aeronautics And Astronautics Fairing skin repair method based on measured wing data
CN111598803A (en) * 2020-05-12 2020-08-28 武汉慧点云图信息技术有限公司 Point cloud filtering method based on variable resolution voxel grid and sparse convolution
CN111598803B (en) * 2020-05-12 2023-05-09 武汉慧点云图信息技术有限公司 Point cloud filtering method based on variable-resolution voxel grid and sparse convolution
WO2021248339A1 (en) * 2020-06-09 2021-12-16 深圳市大疆创新科技有限公司 Point cloud encoding/decoding method and apparatus

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Application publication date: 20170714