JP4709564B2 - Laser measurement method and laser measurement system - Google Patents

Description

  The present invention relates to a laser measurement method performed between an air vehicle and the ground and a laser measurement system using the same, and more particularly to compression transmission of laser pulse emission time data.

  As a laser measurement method for acquiring ground surface unevenness information by irradiating a laser beam from a flying object such as an aircraft, one described in Patent Document 1 below is known. In general, observation data acquired on an aircraft includes information on the emission time, emission position, emission direction, and a plurality of return pulses for each laser pulse to be emitted, and the data size is enormous. For this reason, in the prior art, data acquired on an aircraft is stored in a data recording unit mounted on the aircraft, transferred to a data processor on the ground after measurement, and processed and analyzed.

However, quick response is required for the purpose of use such as grasping the situation on the ground at the time of a disaster, for example. Therefore, development of a laser measurement system that enables data analysis without waiting for the landing of an aircraft is in progress.
JP 2003-156330 A

  In order to improve responsiveness, it is required to send a huge amount of observation data acquired on the aircraft to the ground by wireless transmission, but it is difficult to send the data to the ground in a short time with a limited transmission capacity There was a problem. For this problem, a method of compressing and transmitting the data and expanding it on the ground can be adopted. The compression efficiency also depends on the properties of various data, and how to increase the compression efficiency is an issue to be individually examined for each data type.

  An object of the present invention is to provide a laser measurement method and a laser measurement system with high responsiveness, in particular, improving compression efficiency with respect to laser pulse emission time data, realizing rapid data transmission to the ground.

The laser measurement method according to the present invention is an observation data including a laser pulse emission time data using a laser scanner which is mounted on an aircraft and which repeatedly emits laser pulses according to a predetermined period and scans the ground surface. An observation step of acquiring the observation data on the flying object, a transmission step of transmitting the observation data to the ground base station, and calculating the ground shape by analyzing the observation data in the ground base station during the flight of the flying object. A laser measurement method including a calculation step, wherein the transmission step includes a compression step of compressing at least the emission time data of the observation data on the aircraft and generating compressed time data, A compression step includes a difference step for generating a secondary difference value sequence from the data sequence of the launch time data, and a generation order from the secondary difference value sequence. When the subsequence composed of k secondary difference values (k is an integer equal to or greater than 2) matches any of the numerical sequence patterns registered in advance, the index data associated with the numerical sequence pattern is An association step of associating with the partial sequence; and a forming step of forming the compressed data based on the index data associated with the partial sequence in the association step; The set includes m ^k permutation patterns including m (m is a natural number) representative difference values whose appearance probability in the secondary difference value sequence is equal to or greater than a predetermined value.

  A preferred aspect of the present invention is a laser measurement method in which the representative difference values are −1, 0, and +1.

  In another laser measurement method according to the present invention, the m is 3, the k is 2, and the set of numerical sequence patterns is the latter of the two secondary difference values constituting the partial sequence. Only the secondary difference value of the three includes three special patterns that are arbitrary values other than the representative difference value.

  In another laser measurement method according to the present invention, the index data is represented by 4-bit binary data, and the forming step includes a preceding portion of the two consecutive partial sequences in the association step. A combining step of generating the compressed data of 1 byte by combining the first index data associated with the column and the second index data associated with the subsequent subsequence;

  In another laser measurement method according to the present invention, the k is 2, and the combining step is performed after the two secondary difference values constituting the partial sequence associated with the first index data. 4 bits that can be distinguished from any of the index data in the first index data when only the secondary difference value is any value other than the representative difference value or when the second index data does not exist The compressed identification data of 1 byte is generated by combining the exception identification data.

  In the laser measurement method according to another aspect of the invention, the forming step may include a special difference value other than the representative difference value among the secondary difference values stored in the compressed data, and the compressed data and the subsequent subsequent values. An insertion step of inserting the compressed data in a predetermined format;

The laser measurement system according to the present invention includes observation data including emission time data of the laser pulse, which is mounted on a flying object and uses a laser scanner that repeatedly emits laser pulses according to a predetermined period and scans the ground surface. Is obtained on the aircraft and transmits the observation data, and is installed on the ground, and the observation data is received from the aircraft device during the flight of the aircraft and analyzed to calculate the surface shape. A ground device, and the on-board device includes compression means for compressing at least the launch time data of the observation data on the flying object to generate compressed time data, and the compression means Comprises difference means for generating a secondary difference value sequence from the data sequence of the launch time data, and k secondary difference values extracted from the secondary difference value sequence in the order of generation (k is an integer of 2 or more). When the partial sequence matches any of the numerical value sequence patterns registered in advance, the association means for associating the index data associated with the numerical value sequence pattern with the partial sequence; Forming means for forming the compressed data based on the index data associated with the index data, and the set of numerical value string patterns has an appearance probability in the secondary difference value string equal to or greater than a predetermined value. It includes m ^k permutation patterns composed of representative difference values (m is a natural number).

  In another laser measurement system according to the present invention, the index data is represented by 4-bit binary data, and the forming means is a preceding partial sequence of two consecutive partial sequences by the association unit. The first index data associated with the second index data associated with the subsequent subsequence is combined to generate the compressed data of 1 byte.

  According to the present invention, there is provided a laser measurement method and a laser measurement system in which a plurality of secondary difference values of the emission time data are represented by one index data, thereby further improving the compression efficiency of the emission time data and improving the responsiveness. Realized.

  Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

  FIG. 1 is an explanatory diagram showing an outline of laser measurement using a flying object such as an aircraft or a helicopter. The flying object 1 includes a laser measurement unit 4 and a transmission unit 6, and the laser measurement unit 4 includes a laser scanner 2, a reflected wave reception sensor 8, and a GPS / IMU (Global Positioning System / Inertial Measurement Unit). The

  The laser scanner 2 includes a laser emitting unit 2a that emits laser pulses at predetermined time intervals by a control unit (not shown), and a rotating mirror 2b that enables scanning on the ground by shaking the laser pulses within a predetermined angle range. Is provided. The reflected pulse (return pulse) from the ground surface with respect to the laser emission pulse is detected by the reflected wave receiving sensor 8.

  FIG. 2 is an explanatory diagram showing a return pulse. A plurality of (usually about 1 to 5) reflections from the ground object occur with respect to one emitted laser pulse, and a return pulse can be detected a plurality of times accordingly. The reflected wave receiving sensor 8 outputs the capture time information of the kth return pulse for the nth emission pulse as return pulse data Pkn. The GPS / IMU outputs the GPS position, tilt information, and the like of the flying object 1 at the time of laser pulse emission in synchronization with the laser pulse emission timing of the laser scanner 2.

  The laser data, GPS position, and tilt information may be output as numerical values appropriately made dimensionless by the structure of the laser measuring unit 4, and time information such as laser pulse emission time or return pulse data. For example, the elapsed time from the start of measurement may be used.

  In addition to the return pulse data Pkn and GPS / IMU information, the laser pulse emission time data Tn and the rotation angle data θn of the rotating mirror 2b at that time are acquired as observation data. Wirelessly transmitted. As will be described later, the ground base station calculates the distance between the flying object 1 and the ground surface from the observation data centered on the return pulse data Pkn using the GPS / IMU information as an evaluation element, and calculates the position and height of the ground surface. Calculate.

  FIG. 3 is a block diagram showing the configuration of the laser measurement unit 4 and the transmission unit 6. As described above, the laser measurement unit 4 includes the laser scanner 2, the reflected wave reception sensor 8, and the GPS / IMU, and observation data in the laser scanner 2 and the reflected wave reception sensor 8 is output to the pulse data generation unit 9, and Observation data in the GPS / IMU is output to the GPS / IMU data generation unit 10.

  FIG. 4 is a schematic diagram showing an output format of data from the pulse data generation unit 9. FIG. 5 is a schematic diagram showing an output format of data from the GPS / IMU data generation unit 10. As described above, the pulse data generation unit 9 outputs a data string in which output values corresponding to the emission pulse are arranged in a predetermined order with the emission pulse (laser pulse) as a unit. The example shown in FIG. 4 shows a data format when it is assumed that return pulse data Pkn up to the fifth order can be obtained for each emission pulse, and laser pulse emission time data Tn, The mirror rotation angle data θn and the return pulse data Pkn are stored in this order. Incidentally, as described above, since the return pulse data Pkn is not necessarily acquired up to the fifth order, for example, “0” is stored in the storage position of the order not acquired (see FIG. 14).

  On the other hand, as shown in FIG. 5, the GPS / IMU data generation unit 10 receives GPS time TAn, IMU time TBn, x-direction acceleration VXn, x-direction angle AXn, y-direction acceleration VYn, y-direction angle AYn, z-direction acceleration. VZn and z-direction angle AZn are output. The output values from the GPS / IMU data generation unit 10 are associated with the output values of the pulse data generation unit 9 via a subscript “n” representing a pulse number.

  When laser measurement on the flying object 1 is started, observation data acquired by the laser measurement unit 4 is output to the pulse data generation unit 9 or the GPS / IMU data generation unit 10. The pulse data generation unit 9 and the GPS / IMU data generation unit 10 generate a predetermined data string from the input observation data and output it to the compression unit 11 of the transmission unit 6 (step S1).

  The compression unit 11 includes a data separation unit 11a, a compression processing unit 11b, and an encoding processing unit 11c, and compresses input data. In order to improve immediacy, this compression processing is performed in a relatively small unit of about 4 Mbytes with respect to the entire data capacity.

  As shown in FIG. 4, the data separation unit 11a converts the pulse data output from the pulse data generation unit 9 into three types of data strings SD including laser pulse emission time data Tn, mirror rotation angle data θn, and return pulse data Pkn. (T), SD (θ), and SD (P) are divided (step S2), and each separated data SD is output to the compression processing unit 11b. As shown in FIG. 4, the laser pulse emission time data Tn and the mirror rotation angle data θn in each of the separated data strings SD (T) and SD (θ) are arranged in the order of pulse emission. In the return pulse data Pkn in the separated data sequence SD (P), a data group consisting of five data having the same pulse firing order is arranged in the pulse firing order, and in each data group, five data are in the order of reflection order. Has side-by-side format. In this separated data SD (P), a data end mark is inserted at the boundary of the data group as necessary.

  The compression processing unit 11b performs data compression using different algorithms using the characteristics of each separated data string SD (step S3). FIG. 6 is a graph showing changes in laser emission time data, where the horizontal axis represents the laser pulse emission order and the vertical axis represents the emission time. As shown in this figure, the emission times tend to be distributed on a straight line that rises periodically with respect to the laser pulse emission order. From this property, it is expected that the secondary difference value of the adjacent launch time data Tn will be a small value distributed in the vicinity of 0. By using this secondary difference value, the launch time data can be compressed.

  FIG. 7 is a block diagram showing an outline of the compression processing of the emission time data in the compression processing unit 11b. First, the compression processing unit 11b sequentially generates a secondary difference value sequence (processing P1), and generates a secondary difference value pair in which the generated secondary difference values are combined in order two (processing P2). . The compression processing unit 11b presets an index table TBL that defines the association between the numerical value string pattern that appears in the secondary difference value pair and the index data, and is registered in the secondary difference value pair and the table TBL generated in the process P2. The association process with the index data is performed (process P3). In this process, when a numerical value string pattern that matches the secondary difference value pair exists in the table TBL, index data corresponding to the numerical value string pattern is associated with the secondary difference value pair. The compression processing unit 11b forms compressed data using this index data (processing P4).

  FIG. 8 is a schematic flowchart showing the secondary difference value generation process P1 in the compression process of the laser pulse emission time data Tn. In the following description, the symbol “Tn” represents the firing time of the nth laser pulse, the symbol “Δ1, n” represents the primary difference value (Tn + 1) − (Tn) of the firing time Tn, and the symbol “Δ2,”. n ″ represents the secondary difference value (Δ1, n + 1) − (Δ1, n) of the launch time Tn.

  When generating the secondary difference value sequence S (Δ2, n), first, the buffer area BUF for generating the secondary difference value sequence is set on the memory, and an SOB (Start of Block) mark is inserted at the head (step ST1). ). The SOB has a predetermined predetermined bit length, and is set to a code that does not appear in the following processing. Thereafter, a laser pulse emission time Tn is inserted after the SOB mark. This Tn is used when restoring the separation data string SD (T) of the original launch time from the secondary difference value string.

  Next, the primary difference value Δ1, n is calculated (step ST2), and the sign is determined (step ST3). As described above, since the emission time data Tn tends to be distributed on a straight line that rises periodically and repeats, when the sign of the primary difference value is positive, Tn + 1 related to the primary difference value and When Tn is located along the same straight line, and the sign of the primary difference value is negative, a straight line transfer occurs between Tn + 1 and Tn, and Tn + 1 follows the next straight line. It is considered to be located.

  If the sign is negative, the pulse number n is incremented by 1, and the process is repeated from step ST1. That is, the SOB mark is newly inserted at the end of the buffered data, and then Tn is inserted. For example, if the process from the previous step ST1 is for n = k and (Tk + 1) − (Tk) <0 after inserting Tk, the process from the next step ST1 Tk + 1 is inserted after the SOB mark.

  Incidentally, when the sign of the primary difference value is negative, the SOB mark is inserted as described above, and the SOB mark moves from the straight line to which the previous T value belongs to the evaluation target to a new regression line. Will be shown. That is, each SOB mark has a meaning as a delimiter of a data block corresponding to one straight line.

  On the other hand, if the sign is positive, the obtained primary difference value Δ1, n is inserted after Tn inserted immediately before (step ST4). This Δ1, n is used when restoring the separation data sequence SD (T) of the original launch time from the secondary difference value sequence together with Tn inserted immediately before.

  If the sign is positive, a primary difference value Δ1, n + 1 is further obtained (step ST5). The sign of the primary difference value Δ1, n + 1 is also determined for the same reason as in step ST3 (step ST6). If the sign is negative, the pulse number n is increased by 2 and the processing from step ST1 is performed. Repeatedly, generation of a new data block is started.

  When the sign of Δ1, n + 1 is positive, a secondary difference value Δ2, n is obtained (step ST7), and Δ2, n is inserted after Δ1, n inserted in step ST4 (step ST8). The generation of the secondary difference value is repeated while increasing n by 1 (step ST9). Whether the T value belongs to the next straight line as described above (step ST6), or at the end of the T value. The secondary difference values are sequentially buffered until it reaches (step ST10).

  Note that the straight line in FIG. 6 may vary somewhat depending on the observation accuracy of the launch time data Tn. In this case, if the primary difference value is negative and the absolute value is greater than a predetermined value, it is determined that a straight line transfer has occurred between Tn + 1 and Tn. On the other hand, if the primary difference value is positive or the primary difference value is negative and the absolute value is equal to or less than a predetermined value, it is determined that Tn + 1 and Tn are located along the same straight line.

  Although the original time data Tn can take a large value, the secondary difference value Δ2, n is a small value near 0 as described above, and can be expressed by a shorter data length than the original time data Tn. . For example, even if the original data Tn requires 4 bytes, the secondary difference value Δ2, n can be basically expressed by 1 byte. That is, it can be said that the secondary difference value is already compressed. However, the compression processing unit 11b further compresses the secondary difference values successively inserted into the buffer by the processes P2 to P4 described below, and generates saved data. Hereinafter, the compression process of the secondary difference value sequence will be described.

  FIG. 9 is a schematic diagram showing the structure of the index table TBL used in the process P3. In the figure, the first value (preceding secondary difference value Δ2P), the second value (subsequent secondary difference value Δ2F), and saved data corresponding to the index I shown in the left column Elements E are arranged in the horizontal direction. Here, as described above, most of the secondary difference values are distributed in the vicinity of 0. Empirically, −1, 0, and +1 appear with a high appearance probability in the secondary difference value sequence. Therefore, in the present embodiment, −1, 0, +1 is set as the representative difference value whose appearance probability in the secondary difference value sequence is equal to or greater than a predetermined value, and the index table is defined correspondingly. E is data in which I is binary-displayed. As will be described later, since there are 13 types of indexes I, E can be expressed by substantially 4 bits.

  The indexes I = 0 to 5 and 10 to 12 correspond to nine permutation patterns in which a numerical pattern composed of Δ2P and Δ2F arranges two types of representative difference values (−1, 0, +1).

  In the index I = 6 to 8, Δ2P is one of three types of representative difference values (−1, 0, +1), and Δ2F is a value other than the representative difference value (including the case where Δ2F does not exist) 3 There are two special patterns. In FIG. 9, other than the representative difference value is represented by the symbol “NULL”.

  Index I = 9 defines exception identification data used in exceptional cases. Here, one of the exceptional cases is a case where the secondary difference value extracted as Δ2P is other than the representative difference value (special difference value). In this case, 9 is assigned as the index I using only the secondary difference value extracted as Δ2P without combining subsequent secondary difference values as Δ2F. Another exceptional case is the case where neither Δ2P nor Δ2F is present.

  The compression processing unit 11b sets a data area STR for storing compressed data on the memory when starting the compression processes P1 to P4. The compression processing unit 11b stores data in the above-described buffer BUF in the secondary difference value sequence generation process P1, and sequentially extracts data from the buffer BUF in processes P2 to P4.

  In the process P2, when the data extracted from the buffer BUF is the SOB mark, Tn, Δ1, n, the compression processing unit 11b transfers the data as it is to the data area STR.

  On the other hand, when the data extracted from the buffer BUF is the secondary difference value Δ2, n, the compression processing unit 11b also extracts the subsequent secondary difference value Δ2, n + 1 to generate a secondary difference value pair. (Process P2), matching with a pattern composed of Δ2P and Δ2F of the table TBL is performed to determine a storage data element E1 corresponding to the secondary difference value pair (Process P3).

  When the secondary difference value pair is a combination of representative difference values I = 0 to 5 and 10 to 12, the compression processing unit 11b, as a rule, further follows the secondary difference values Δ2, n + 2, Δ2 , n + 3, the storage data element E2 is similarly determined for the secondary difference value pair. Then, E1 is the upper 4 bits, E2 is the lower 4 bits, and both are combined to generate 1-byte storage data ES, which is additionally stored in the compressed data storage data area STR (process P4).

  FIG. 10 is a schematic diagram for explaining the compressed data forming process P4. FIGS. 10A to 10C show cases where the index I of the above-described second-order differential value pair is 0 to 5, 10 to 12, respectively. FIGS. 10A and 10B correspond to the principle case where the stored data ES is generated based on the four secondary difference values, and FIG. 10A shows the index I of the subsequent secondary difference value pair. Is also a case where 0 to 5, 10 to 12, and FIG. 10B is a case where the index I of the subsequent secondary difference value pair is 6 to 8.

  On the other hand, FIGS. 10C and 10D are exceptional cases where the storage data ES is generated based on three or two secondary difference values, and the index I = 9 is stored as the storage data element E2. Corresponding data is assigned. Similarly to the case of FIGS. 10A and 10B, E1 is the upper 4 bits and E2 is the lower 4 bits, and both are combined to generate 1-byte storage data ES, which is a compressed data storage data area STR. (Process P4).

  Here, FIG. 10C shows a case where the secondary difference value extracted as Δ2, n + 2 is other than the representative difference value. As will be described later, when a secondary difference value (special difference value) other than the representative difference value appears, as a part of the process P4, a process of storing the special difference value in the data area STR is performed. The processing for the next difference value is continued after the processing for storing the special difference value. Therefore, the secondary difference value subsequent to the secondary difference value extracted as Δ2, n + 2 is not extracted as Δ2, n + 3, and data corresponding to the index I = 9 is assigned as the storage data element E2.

  FIG. 10D shows a case where Δ2, n + 1 is a special difference value. Also in this case, the subsequent secondary difference value is not extracted as Δ2, n + 2, Δ2, n + 3, and corresponds to the index I = 9 as the saved data element E2 for the convenience of shifting to the processing for storing the special difference value. Assign data to be used.

  Incidentally, in the case shown in FIG. 10B, Δ2, n + 3 is a special difference value, and after storing the stored data ES in the data area STR, a special difference value storage process is performed. Further, the case where Δ2, n is a special difference value is not shown in FIG. 10, but in this case, the storage data ES consisting of the combination of the storage data elements is not generated, but the preceding storage data is directly generated. Following the ES, the special difference value is additionally stored.

  The special difference value storage process is a process of adding data (special storage data EE) in a predetermined format that can be identified between the preceding storage data ES and the subsequent storage data ES to the data area STR. It is. For example, the first byte of the special storage data EE is a data header that can be distinguished from any storage data ES. For example, the data header can be “0xFF”. Following the data header, 1 to 4 bytes of variable length data is added. The data length of the variable length data is defined so as to be expressed by using some predetermined bits of the second byte, for example. When decompressing the compressed data on the ground base station side, based on the contents of the predetermined bit, it is determined to what byte the special storage data EE starting from the data header is up to, and the storage data ES from the subsequent bytes again. I can grasp it. The special difference value is represented using the remaining bits of the variable length data.

  As already described, most secondary difference values are representative difference values due to the nature of the launch time data. When the representative difference values are continuous by the processes P2 to P4 described above, the four representative difference values are represented by 1-byte storage data ES. That is, it is possible to further improve the compression efficiency of the emission time data as compared with the case where individual secondary difference values are stored as saved data.

  Next, a compression operation for the mirror rotation angle data θn will be described. The mirror rotation angle data θn on the vertical axis and the laser pulse emission order on the horizontal axis, the laser pulse emission order-mirror rotation angle diagram can be approximated as a sine curve. The value is stored data. In addition, unlike the above-described laser pulse emission time, the regression line does not have discontinuous points in the entire region. For this reason, since there is no concern that the data length becomes excessively large by storing the difference value at the jump point, it is not necessary to set a data block delimited by the SOB mark, and it is sufficient to simply connect the secondary difference values. In order to be able to calculate the original data from each compressed value that is the secondary difference value, the original data and then the primary difference value are inserted at the beginning of the compressed data, followed by the secondary difference value.

  FIG. 11 is a schematic diagram illustrating an example of compression of the mirror rotation angle data θn. The table on the left shows the original data and calculation progress, and shows which elements in this table are stored as saved data (compressed data) shown on the right. The original data is shown vertically, the “row” column corresponds to the firing order of the laser pulses, and the example mirror rotation angle data θn is 100 for the first shot, and thereafter 200, 301, 400, ... and it continues.

  If there is such original data, first, the original data “100” at the head is extracted as saved data 1 (step Sθ1). Thereafter, in step Sθ2, the primary difference between the second original data “200” and the head original data “100” is calculated, and the calculation result “100” is registered as saved data 2 as subsequent data of saved data 1. Next, the secondary difference “1” obtained from the primary difference “101” between the third original data “301” and the second original data “200” and the primary difference “100” obtained in step Sθ2 is obtained. The saved data 3 is registered following the saved data 2 (step Sθ3). Thereafter, the same procedure as step Sθ3 is repeated, and the secondary differences are sequentially registered as saved data to complete the process.

  FIG. 12 is a schematic diagram showing a data format for storing secondary difference of compressed data obtained by the above procedure. As described above, the first original data and the primary difference data exist before this data format, but are not shown here. As shown in FIG. 12, since the secondary difference is a small value, it can be expressed by about 6 bits, and is stored in an 8-bit (1 byte) length obtained by adding two kinds of state determination bits to this.

  The state determination bits are a positive / negative determination bit and an error determination bit each having a length of 1 bit. The positive / negative determination bit is determined by the positive / negative of the secondary difference. The error determination bit indicates that an error value is stored when it cannot be described with a 6-bit length. In the present embodiment, in a state where an error bit is set, the secondary difference is stored in an area extended by 2 bytes.

  The compression procedure of the return pulse Pkn will be described with reference to FIGS. FIG. 13 is a schematic diagram showing the flow of compression processing, and the upper frame is the separated data string SD (P) shown in FIG. As shown in FIG. 13, in the separated data string SD (P), five return pulse data (P1n, P2n,..., P5n) areas are secured for one laser pulse, and return pulse data Pkn. “0” is stored in the portion where there is no symbol. As shown in FIG. 2, the return pulse is obtained by reflecting a laser pulse leaking from between leaves in a tree in a forest or the like to another reflector located on the ground surface side, so that all regions are buried. Even if a small value such as “0” indicates “no value”, an area having the same predetermined bit length as that for storing other return pulse data values is allocated. It is done.

  In order to eliminate the data redundancy associated with such a data structure, first, the data structure is changed (step SP1). In carrying out step SP1, header information “Head_n” indicating the data filling in the area for storing the return pulse data group (P1n, P2n,..., P5n) for the nth laser pulse is introduced and “no value” “Delete the data. In the present embodiment, a 1-byte area is given to the header information Head_n, and the final order and return pulse data storage position are indicated by the lower 5 bits. For example, if only the primary return pulse data P1n exists and the secondary and subsequent values are “no value”, the header information Head_n is given as “00000001” and exists up to the tertiary return pulse data P3n. When there is no next return pulse and primary and tertiary return pulses are present, “00000101” is given, and when all are filled, “00011111” is given. As a result, the data string is described by the header information Head_n and the actual data as shown in the middle frame of FIG.

  Next, the difference between the data is taken as storage data (step SP2). In step SP2, the stored data is determined while performing the Q calculation and the R calculation, and the compressed data string includes header information Head_n, Q value for the pulse number “n” as shown in the lower frame of FIG. Stored in the order of “Q1n” and R value “Rkn”. The subscript “k” of the R value Rkn indicates the return order. As will be described later, for the primary return pulse data P1n, the Q value Q1n, which is the difference from the immediately preceding primary return pulse data (P1, n-1), is stored data, so k is 2 or more. It becomes an integer of 5 or less.

  Q calculation and R calculation will be described with reference to examples shown in FIGS. Here, FIG. 14 is a schematic diagram showing a specific example of the separated data string SD (P). FIG. 15 is a schematic diagram of saved data generated corresponding to the separated data string of FIG.

  The original data shown in FIG. 14 indicates that only the primary return pulse is obtained for the laser pulse number “1” and its value is “100”. Further, for the laser pulse number “7”, the return pulse up to the fifth order is captured, and the value is shown to be “700, 800, 810, 820, 850” from the primary side. .

  First, as the initial information, only the primary return pulse of the laser pulse number “1” is acquired. Therefore, after storing “00000001” in the header information Head_n, “100” is directly used as the primary return pulse data P11. Store. In order to facilitate the description, the stored data is represented by using an array Cmp of k rows and n columns, and the original data is represented by an array Org of k rows and n columns. For example, the fact that the leading data “100” has been stored as saved data can be known by substituting Org (1,1) for Cmp (1,1).

  Here, since the header information Head_1 indicates that only the primary pulse data is stored, the processing for the first laser pulse is completed without searching for the secondary return pulse. Next, the process proceeds to the second (n = 2) laser pulse processing.

After n = 2, the Q value is calculated first. Q calculation is an operation for obtaining a difference between primary return pulses with respect to adjacent laser pulses,
Q1n = P1n-P1, n-1
Given in.

In this example, since n = 2,
Q12 = P12-P11
= Org (1,2) -Org (1,1)
= 200-100 = 100
This is assigned to Cmp (1,2).

When the Q calculation is completed, the R calculation is performed with the same n value. R calculation is an operation for taking a difference between adjacent values in the same row of the Org array,
Rkn = Pkn-Pk-1, n
Given in. In the example of FIGS.
R22 = P22-P12
= Org (2,2) -Org (1,2)
= 300-200 = 100
Is substituted into Cmp (2,2).

  The R calculation is continued until the return pulse data Pkn of the same laser pulse number is completed, and thereafter, the above-described procedure, that is, the assignment of header information Head_n, one Q calculation, and an appropriate number of R calculations are repeated. .

  The Cmp array obtained in this way is arranged in a one-dimensional array (bit string) to be a data string to be compressed.

  When the compression processing for each separated data string SD is completed as described above, the combination processing is performed and the files are combined into one file, and then the encoding processing in the encoding processing unit 11c shown in FIG. 3 is performed (step S4). . Entropy encoding or the like can be used for the encoding process.

  When the encoding process is completed, first, streaming is performed in the streaming unit 12 to enable analysis at the ground base station during data transmission (step S5), and then the transmission data conversion processing unit 13 shapes the carrier wave. (Step S6) and transmitted from the output unit 14 (step S7).

  In the above embodiment, only the pulse data is compressed and the GPS / IMU data is directly transmitted as it is. However, the GPS / IMU data is also compressed and transmitted. Is also possible. Incidentally, GPS / IMU data can be transmitted using a period of turning and moving to the measurement route.

  The transmission unit 6, the pulse data generation unit 9, and the GPS / IMU data generation unit 10 can be achieved by using a computer program that causes a computer to perform the function.

  FIG. 16 is a block diagram of a ground base station that receives transmission information from an aircraft. The terrestrial base station has a data reproduction unit 7 including a reception processing unit 15 and a restoration processing unit 16. When the reception unit 15a of the reception processing unit 15 receives the compressed data from the flying object 1, the streaming processing unit 15b performs a streaming process so that subsequent data analysis can be performed while receiving the data (step SG1). It outputs to the decoding part 16a of the decompression | restoration process part 16 (step SG2).

  FIG. 17 is an explanatory diagram illustrating the decompression process of compressed data. In the decoding unit 16a, the encoding and combination of the compressed data file are canceled to return to the state before encoding, and further, the restoring unit 16b performs restoration processing (step SG3). By the restoration process, as shown in the middle part of FIG. 17, the emission time data Tn, the mirror rotation angle data θn, and the return pulse data Pkn are each in the state of the separated data string SD and are combined in the data combining unit 16c (step SG4), as shown in the lower part of FIG. 17, the output from the pulse data generation unit 9 is reproduced.

  The combined data is analyzed by the data analysis unit 5 and the measurement result by the return pulse group is calculated. In the analysis, the observation data is temporarily stored in the pulse data / GPS / IMU data storage unit 5a (step SG5), and the actual position and the like are calculated in the actual distance / coordinate processing unit 5b (step SG6). The actual distance / coordinate processing unit 5b uses an internal rating element based on the characteristics of the optical system of the aircraft 1 and an external rating element based on GPS / IMU data on a predetermined projection space of the reflection part of the return pulse. Calculate the position and height. In general, the number of data from the GPS / IMU is a fractional number compared to the number of laser pulses emitted and does not correspond one-to-one. Therefore, as described above, laser data other than the laser data corresponding to the subscript “n” For the external rating element for, an interpolated value for the acquired GPS / IMU data is used.

  Since each point data obtained in this way has three-dimensional information, it is also possible to display the ground surface in a stippled pattern using this. The data is stored in the point data storage unit 17 (step SG7).

  Furthermore, in this embodiment, the 3D processing unit 18 is provided in the ground base station. The 3D processing unit 18 includes a 3D data generation unit 18a for forming a 3D image including, for example, a three-dimensional polygon and a texture based on the point data group. The data generated by the 3D data generation unit 18a is stored in the generated 3D data 18b and displayed on the 3D data display unit 18c as desired.

  Further, the ground base station is provided with a comparison unit 19 so that information such as crustal movement, disaster, etc. can be obtained immediately using quick response. The comparison unit 19 includes existing 3D data 19a, a difference data generation unit 19b, and the 3D data display unit 18c. The output from the 3D data generation unit 18a is compared with the existing 3D data 19a in the difference data generation unit 19b, and a difference on the image is detected. The detection result is displayed on the 3D data display unit 18c, and can be instructed to re-measure or expand the measurement range to the flying vehicle 1 as necessary.

  In the above, the data reproduction unit 7, the data analysis unit 5, the 3D processing unit 18, and the comparison unit 19 can also be achieved by a computer program that causes a computer to operate so as to exhibit the functions.

It is explanatory drawing which shows the outline | summary of the laser measurement using flying bodies, such as an aircraft and a helicopter. It is explanatory drawing which shows a return pulse. It is a block diagram which shows the structure of a laser measurement part and a transmission part. It is a schematic diagram which shows the output format of the data from a pulse data generation part. It is a schematic diagram which shows the output format of the data from a GPS / IMU data generation part. It is a graph which shows the change of laser emission time data. It is a block diagram which shows the outline | summary of the compression process of the discharge time data in a compression process part. It is a general | schematic flowchart which shows the secondary difference value sequence production | generation process P1 in the compression process of the laser pulse emission time data Tn. It is a schematic diagram which shows the structure of the index table TBL used by the matching process P3. It is a schematic diagram explaining the compressed data formation process P4. It is a schematic diagram which shows the example of compression of mirror rotation angle data (theta) n. It is a schematic diagram which shows the data format for the secondary difference storage of compressed data. It is a schematic diagram which shows the flow of a compression process of mirror rotation angle data (theta) n. It is a schematic diagram which shows the specific example of separation data sequence SD (P). It is a schematic diagram of the preservation | save data produced | generated corresponding to the separation data sequence of FIG. It is a block diagram of a ground base station that receives transmission information from a flying object. It is explanatory drawing which shows the decompression | restoration process of compressed data.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Aircraft, 2 Laser scanner, 3 Data block, 4 Laser measurement part, 5 Data analysis part, 6 Transmission part, 7 Data reproduction part, 11 Compression part, 11a Data separation part, 11b Compression processing part, 11c Encoding processing part .

Claims (9)

An observation that is mounted on a flying object and that obtains observation data including the emission time data of the laser pulse on the flying object using a laser scanner that repeatedly emits laser pulses according to a predetermined period and scans the ground surface. A laser measurement method comprising: a transmission step for transmitting the observation data to a ground base station; and a calculation step for calculating the surface shape by analyzing the observation data in the ground base station during the flight of the flying object. There,
The transmission step includes a compression step of compressing at least the launch time data of the observation data on the aircraft and generating compressed time data,
The compression step includes
A difference step for generating a secondary difference value sequence from the data sequence of the launch time data;
Index data associated with a numerical sequence pattern when a partial sequence consisting of two secondary differential values extracted from the secondary differential value sequence in the order of generation matches one of the previously registered numerical sequence patterns Associating with the subsequence,
Forming the compressed data based on the index data associated with the partial sequence in the association step;
Have
The value set in train pattern, the secondary differential value permutation pattern of nine that probability of occurrence arranged two three representative difference value is above a predetermined value in the column, and two of the constituting the partial sequence Only the secondary difference value after the secondary difference value includes three special patterns that are arbitrary values other than the representative difference value.
A laser measurement method characterized by the above. The laser measurement method according to claim 1,
The index data is represented by 4-bit binary data,
The forming step combines the first index data associated with the preceding partial sequence and the second index data associated with the subsequent partial sequence of the two consecutive partial sequences in the association step. Generating a 1-byte compressed data,
In the combining step, only the subsequent secondary difference value of the two secondary difference values constituting the partial sequence associated with the first index data is an arbitrary value other than the representative difference value. Or when the second index data does not exist, generating 1-byte compressed data by combining the first index data with 4-bit exception identification data that can be identified with any of the index data;
A laser measurement method characterized by the above. An observation that is mounted on a flying object and that obtains observation data including the emission time data of the laser pulse on the flying object using a laser scanner that repeatedly emits laser pulses according to a predetermined period and scans the ground surface. A laser measurement method comprising: a transmission step for transmitting the observation data to a ground base station; and a calculation step for calculating the surface shape by analyzing the observation data in the ground base station during the flight of the flying object. There,
The transmission step includes a compression step of compressing at least the launch time data of the observation data on the aircraft and generating compressed time data,
The compression step includes
A difference step for generating a secondary difference value sequence from the data sequence of the launch time data;
Index data associated with a numerical sequence pattern when a partial sequence consisting of two secondary differential values extracted from the secondary differential value sequence in the order of generation matches one of the previously registered numerical sequence patterns Associating with the subsequence,
Forming the compressed data based on the index data associated with the partial sequence in the association step;
Have
The set of numerical sequence patterns includes m ² permutation patterns in which ^two types of representative difference values (m is a natural number) in which the appearance probability in the secondary difference value sequence is a predetermined value or more are arranged .
The index data is represented by 4-bit binary data,
The forming step combines the first index data associated with the preceding partial sequence and the second index data associated with the subsequent partial sequence of the two consecutive partial sequences in the association step. Generating a 1-byte compressed data,
In the combining step, only the subsequent secondary difference value of the two secondary difference values constituting the partial sequence associated with the first index data is an arbitrary value other than the representative difference value. Or when the second index data does not exist, generating 1-byte compressed data by combining the first index data with 4-bit exception identification data that can be identified with any of the index data;
A laser measurement method characterized by the above. In the laser measuring method according to claim 2 or claim 3,
The forming step, a special difference values other than the representatives difference integral value of the stored in the compressed data said secondary difference values, inserted in a predetermined format between the compressed data and succeeding the compressed data And a laser measuring method characterized by comprising an insertion step. In the laser measuring method according to any one of claims 1 to 4 ,
The representative differential value is -1, 0, and +1. The observation data including the emission time data of the laser pulse is acquired on the aircraft using a laser scanner that is mounted on the aircraft and repeatedly emits laser pulses according to a predetermined period to scan the ground surface. An on-board device for measuring and transmitting the observation data;
A ground device that is installed on the ground, receives the observation data from the onboard device during the flight of the flying object and analyzes it to calculate the surface shape;
Have
The onboard device is:
Compression means for compressing at least the launch time data of the observation data on the aircraft and generating compressed time data;
The compression means includes
Difference means for generating a secondary difference value sequence from the data sequence of the launch time data;
Subsequence consisting of two second-order difference value extracted in the order of generation from the secondary differential value column, if it matches any of the numeric string patterns registered in advance, the index data associated with the numerical sequence pattern Associating means for associating
Forming means for forming the compressed data based on the index data associated with the partial sequence by the association means;
Have
The set of numerical sequence patterns includes nine permutation patterns in which two types of representative difference values having an appearance probability in the secondary difference value sequence equal to or higher than a predetermined value are arranged , and two of the above-described partial sequences. Only the secondary difference value after the secondary difference value includes three special patterns that are arbitrary values other than the representative difference value .
A laser measurement system characterized by The observation data including the emission time data of the laser pulse is acquired on the aircraft using a laser scanner that is mounted on the aircraft and repeatedly emits laser pulses according to a predetermined period to scan the ground surface. An on-board device for measuring and transmitting the observation data;
A ground device that is installed on the ground, receives the observation data from the onboard device during the flight of the flying object and analyzes it to calculate the surface shape;
Have
The onboard device is:
Compression means for compressing at least the launch time data of the observation data on the aircraft and generating compressed time data;
The compression means includes
Difference means for generating a secondary difference value sequence from the data sequence of the launch time data;
Index data associated with a numerical sequence pattern when a partial sequence consisting of two secondary differential values extracted from the secondary differential value sequence in the order of generation matches one of the previously registered numerical sequence patterns Associating means for associating
Forming means for forming the compressed data based on the index data associated with the partial sequence by the association means;
Have
The set of numerical sequence patterns includes m ² permutation patterns in which m types of representative difference values having an appearance probability in the secondary difference value sequence equal to or higher than a predetermined value are arranged ,
The index data is represented by 4-bit binary data,
The forming means combines the first index data associated with the preceding partial sequence and the second index data associated with the subsequent partial sequence in the continuous two partial sequences. have a binding means for generating the compressed data of 1 byte Te,
In the combining means, only the subsequent secondary difference value of the two secondary difference values constituting the partial sequence associated with the first index data is an arbitrary value other than the representative difference value. Or when the second index data does not exist, generating 1-byte compressed data by combining the first index data with 4-bit exception identification data that can be identified with any of the index data;
A laser measurement system characterized by The laser measurement system according to claim 7,
The forming means inserts a special difference value other than the representative difference value among the secondary difference values stored in the compressed data in a predetermined format between the compressed data and the subsequent compressed data. A laser measuring system characterized by comprising means. In the laser measurement system according to any one of claims 6 to 8,
The representative difference value is -1, 0, and +1.

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