CN107817501B - Point cloud data processing method with variable scanning frequency - Google Patents
Point cloud data processing method with variable scanning frequency Download PDFInfo
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- CN107817501B CN107817501B CN201711025506.8A CN201711025506A CN107817501B CN 107817501 B CN107817501 B CN 107817501B CN 201711025506 A CN201711025506 A CN 201711025506A CN 107817501 B CN107817501 B CN 107817501B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
- G01S17/46—Indirect determination of position data
- G01S17/48—Active triangulation systems, i.e. using the transmission and reflection of electromagnetic waves other than radio waves
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C7/00—Tracing profiles
- G01C7/02—Tracing profiles of land surfaces
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- General Physics & Mathematics (AREA)
- Radar, Positioning & Navigation (AREA)
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- Computer Networks & Wireless Communication (AREA)
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- Optical Radar Systems And Details Thereof (AREA)
Abstract
The invention relates to the technical field of spatial ranging, in particular to a point cloud data processing method with variable scanning frequency. The method comprises the steps that two groups of emission data with different emission frequencies are set, the laser radar periodically switches the two groups of data to carry out laser emission, the first group of emission data is used for obtaining accurate topographic information of a measuring area, and the reasonable return period of each laser emission point emitted by the second group of emission data is calculated through the topographic information, so that accurate distance information is obtained, and the problem of multiple periods of laser receiving time in the prior art is solved; in addition, the second group of emission frequencies can be set autonomously according to needs, the point cloud density obtained by the higher emission frequency is higher, and the distance data measured in the measurement area is more accurate.
Description
Technical Field
The invention relates to the technical field of spatial ranging, in particular to a point cloud data processing method with variable scanning frequency.
Background
The laser radar is a device for measuring distance by using laser, and the distance of a plurality of measuring points is reduced to a space coordinate, so that the space reduction of the surrounding environment is finally realized. The time taken for the laser to be emitted to be received determines the accuracy of the measurement, and the number of times the laser is emitted per unit time determines the data density in the point cloud. In the process that the aircraft utilizes the laser radar to measure the ground distance, the receiving time of the laser has a multi-cycle problem due to the long distance.
The laser radar emits laser according to a given period, for an emission point P1 at the time of T1, the receiving time is taken as T1, and if the laser returns to the emitter in the period T, the distance measurement value at the time can be obtained as [ speed of light x (T1-T1)/2 ] according to the reflection time and the speed of light. If the laser light is not reflected back to the emitter during period T, the emitter will emit the next emission point P2 at time T2. There will now be two emission points P1, P2 running on the emission or reflection path simultaneously. When the point P1 returns to the transmitter, the transmitter cannot distinguish whether the returning laser light is emitted at the time T1 or T2, thus causing a false determination of the time of flight calculation of P1.
The conventional solution to the problem of multi-cycle laser reception time is to estimate the flight time of point P according to the altitude and terrain of the aircraft, which can be returned within several cycles T, and convert the reflection time when processing data. However, before the measurement is performed by using the laser radar, it is difficult to obtain accurate topographic data, so that the accuracy of the finally obtained distance measurement value is also low.
Disclosure of Invention
In order to overcome at least one defect in the prior art, the invention provides a point cloud data processing method with variable scanning frequency, which simultaneously acquires topographic information in the distance measurement process, applies the acquired topographic information to data analysis, and calculates the return period of a laser emission point, thereby accurately restoring the distance measurement value.
In order to solve the technical problems, the invention adopts the following technical scheme:
a point cloud data processing method with variable scanning frequency adopts a laser radar to carry out point cloud collection, and comprises the following steps:
s1: setting two groups of emission data with different emission frequencies for the laser radar, wherein laser energy emitted according to the first group of emission data returns to the laser radar in one period, and the emission frequency of the second group of emission data is the required highest emission frequency;
s2: based on the execution of the step S1, the laser radar periodically switches two sets of data for laser emission, thereby performing point cloud collection;
s3: processing the data collected in the step S2, and firstly, obtaining topographic information by using point cloud data obtained by emitting the first group of emission data;
s4: a reasonable return period of each laser emission point emitted with the second set of emission data is calculated based on the topographic information obtained at step S3, thereby obtaining accurate distance information.
Further, the transmission frequency of the first set of transmission data is obtained by dividing the speed of light by twice the farthest distance from the first lidar in the measurement region. And calculating the critical frequency of the emitted laser energy to return to the laser radar in one period, and emitting the laser at the emission frequency less than or equal to the frequency, so that the laser can be ensured to return to the laser radar in one period.
Further, the maximum transmitting frequency required in step S1 is determined by taking the allowable maximum scanning frequency, i.e., the transmitting frequency of the second group of laser beams is dynamically adjusted according to the data collected by the first group of laser beams, based on the flight altitude of the aircraft, the terrain (obtained from the data collected by the first group of laser beams), and the relationship between the frequency of the laser radar itself and the corresponding scanning distance.
Further, the topographic information is obtained by filtering the point cloud data obtained from the laser emitted with the first set of emission data in step S3.
Compared with the prior art, the beneficial effects are: the method comprises the steps that two groups of emission data with different emission frequencies are set, the laser radar periodically switches the two groups of data to carry out laser emission, the first group of emission data is used for obtaining accurate topographic information of a measuring area, and the reasonable return period of each laser emission point emitted by the second group of emission data is calculated through the topographic information, so that accurate distance information is obtained, and the problem of multiple periods of laser receiving time in the prior art is solved; in addition, the second group of emission frequencies can be set autonomously according to needs, the point cloud density obtained by the higher emission frequency is higher, and the distance data measured in the measurement area is more accurate.
Drawings
FIG. 1 is a flow chart of an embodiment of the present invention.
Detailed Description
The invention is further described with reference to the accompanying drawings, which are meant to be illustrative only and not to be construed as limiting the patent.
As shown in fig. 1, a method for processing point cloud data with variable scanning frequency, which uses a laser radar to collect point cloud, includes the following steps:
s1: setting two groups of emission data with different emission frequencies for the laser radar, wherein laser energy emitted according to the first group of emission data returns to the laser radar in one period, and the emission frequency of the second group of emission data is the required highest emission frequency;
s2: based on the execution of the step S1, the laser radar periodically switches two sets of data for laser emission, thereby performing point cloud collection;
s3: processing the data collected in the step S2, firstly, filtering the point cloud data obtained by emitting the first group of emission data to obtain topographic information;
s4: a reasonable return period of each laser emission point emitted with the second set of emission data is calculated based on the topographic information obtained at step S3, thereby obtaining accurate distance information.
In this example, the lidar used is a rigel VUX-1 device. It should be noted that the present invention is applicable to various laser radars, and the rigel VUX-1 apparatus is a laser radar used in the present embodiment, and should not be construed as limiting the present invention.
In this embodiment, the farthest distance from the lidar within one periodic measurement region is no more than 394.7 meters. The transmission frequency 380khz of the first set of transmission data and the transmission frequency 550khz of the second set of transmission data are taken. Wherein the emission frequency of the first set of emission data is obtained by dividing the speed of light by twice the farthest distance from the first lidar in the measurement region, i.e. the speed of light is 3E 8/(394.7 × 2) =380 khz; at this time, the farthest ranging value in one period of the first set of transmission data is 394.7 m, and the farthest ranging value in one period of the second set of transmission data is 272.7 m. In the measuring area, the distance between each target and the laser radar can be identified to be less than 272.7 meters or 272.7-394.7 meters through the laser emitted by the first group of emission data, whether the laser point emitted by the second group of emission data returns in one period or the second period is judged according to the result, and the distance measurement value can be accurately restored in the distance measurement data calculation process of the laser emitted by the second group of emission data. In addition, in the embodiment, because two sets of data are adopted for laser transmission, the point cloud density is greatly increased, and the precision of the ranging data is obviously improved.
It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.
Claims (3)
1. A point cloud data processing method with variable scanning frequency adopts a laser radar to carry out point cloud collection, and is characterized by comprising the following steps:
s1: setting two groups of emission data with different emission frequencies for the laser radar, wherein the laser energy emitted according to the first group of emission data returns to the laser radar in one period, the emission frequency of the second group of emission data is the required highest emission frequency, and the highest emission frequency is comprehensively considered according to the flight height of the airplane, the terrain condition, the frequency of the radar and the relation between the corresponding scanning distances, and the allowed highest scanning frequency is selected;
s2: based on the execution of the step S1, the laser radar periodically switches two sets of data for laser emission, thereby performing point cloud collection;
s3: processing the data collected in the step S2, and firstly, obtaining topographic information by using point cloud data obtained by emitting the first group of emission data;
s4: a reasonable return period of each laser emission point emitted with the second set of emission data is calculated based on the topographic information obtained at step S3, thereby obtaining accurate distance information.
2. The method for processing point cloud data with variable scanning frequency according to claim 1, wherein: the transmitting frequency of the first group of transmitting data is obtained by dividing the speed of light by twice the farthest distance from the first laser radar in the measuring area.
3. The method as claimed in claim 1, wherein the topographic information is obtained by filtering the point cloud data obtained from the laser emitted from the first set of emission data in step S3.
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| CN109324398B (en) | 2019-01-02 | 2019-04-02 | 江西联益光学有限公司 | Optical imaging lens and imaging device |
| WO2020142928A1 (en) * | 2019-01-09 | 2020-07-16 | 深圳市大疆创新科技有限公司 | Ranging device, application method for point cloud data, perception system, and mobile platform |
| CN114026461A (en) * | 2020-05-19 | 2022-02-08 | 深圳市大疆创新科技有限公司 | Method for constructing point cloud frame, target detection method, distance measuring device, movable platform and storage medium |
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| EP2165214B1 (en) * | 2007-06-15 | 2012-03-14 | University of Limerick | A method and apparatus for determining the topography of a seafloor and a vessel comprising the apparatus |
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| JP2003167048A (en) * | 2001-12-03 | 2003-06-13 | Hitachi Ltd | Two-frequency cw system radar |
| CN1651856A (en) * | 2005-02-08 | 2005-08-10 | 王治平 | Laser digital angle measuring method and apparatus thereof |
| CN105093925A (en) * | 2015-07-15 | 2015-11-25 | 山东理工大学 | Measured-landform-feature-based real-time adaptive adjusting method and apparatus for airborne laser radar parameters |
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