KR100312410B1 - Method for compression and ecompression of vector data in ageographic information system - Google Patents

Abstract

1. Technical field to which the invention described in the claims belongs

The present invention relates to a vector data compression and decompression method in a geographic information system.

2. The technical problem to be solved by the invention

The present invention converts planar rectangular coordinates of vector data into relative screen coordinates in a server of a geographic information system (GIS) having a client / server structure, converts these values into bits, and stores them in accordance with their size. We want to provide a restoration method by receiving the data from the server.

3. Summary of Solution to Invention

In the method of compressing and restoring vector data applied to a client / server geographic information system, the server converts planar rectangular coordinates of vector data into relative screen coordinates, and converts the converted relative screen coordinates into characteristics of vector data. The range of X ("X") absolute value and Y ("Y") absolute value for classifying vector data according to the vector data type by converting into bits according to the data is determined. A first step of determining and storing a bit representing a number and a number; And a fraudulent client receives the reference absolute coordinates and the vector data from the server, and discriminates the delimiter bits and the consecutive bits of the compressed data according to the type of the vector data, and selects X ("X") from the bits representing the sign bits and the number. And a second step of restoring the original data which is the Y ("Y") coordinate value.

4. Important uses of the invention

The present invention is used for geographic information system

Description

Method for compression and ecompression of vector data in ageographic information system}

The present invention converts planar rectangular coordinates of vector data into relative screen coordinates in a server of a geographic information system (GIS) of a client / server structure, stores these values in several defined types, and compresses them in the client. The present invention relates to a method of compressing and restoring vector data that reduces the amount of vector data transmitted by restoring data, thereby enabling a faster user response, and a computer-readable recording medium having recorded thereon a program for realizing the same.

Data compression refers to physically reducing the size of various files handled by a computer.

Compression and decompression of data is a very important technology in the fields of distributed computing systems, data communication, computer networks, video and audio processing, and is applied to efficiently use storage devices and communication resources.

Data compression techniques include Huffmann coding, Run-Length Coding, Prediction, Conversion, and Motion Compensation.

Since the above compression methods are intended for document, image, video and audio data, it is inevitable to introduce the document compression method to compress vector data files of graphics, but the amount of raw data itself to be compressed is huge. Fast data transfer time cannot be guaranteed unless the data compression rate is high.

In general, the vector data format of an electronic map varies greatly depending on the GIS tool used, and includes Data eXchange Format (DXF), Spatial Data Transfer Standard (SDTS), National Transfer Format (NTF), and Digital Geographic Information Exchange Standard (DIGEST). Store and retrieve raw data built in standard formats such as the GIS tool's own format.

If you store a vector coordinate value (X ₁ , Y ₁ ) representing a point in the real world in ASCII (American National Standard Code for Information interchange) type, "(X value representation character + Y value representation indefinite number) X 1 byte. ", And storing it in the previous double-precision floating point type requires 16 bytes of storage. The GIS tool calculates the relative coordinate values of the vector data, or the coordinates of the real system. The method converts to value integer and stores (X ₁ , Y ₁ ) in Floating Point type or Integer type, which requires 8 bytes of storage space. By reducing raw data to a 2: 1 level, higher processing performance and faster user response time are achieved.

However, even if the vector data is stored in its own format as described above, in the conventional client-server structure geographic information system in which the spatial data processor and the user application which perform the map search operation do not exist in the same computer, the vector data is stored. The network transfer took a considerable time.

However, in the conventional method, the vector data transmission amount can be shortened by the server performing the screen coordinate conversion work performed by the client and applying the relative screen coordinate system, but the compression rate is reduced by processing the uniform data type. have.

In order to solve the above problems, the present invention converts the planar rectangular coordinates of the vector data into the state screen coordinates in a server of a geographic information system (GIS) having a client / server structure, and converts the values into bits to convert the size into bits. A method of compressing and restoring vector data for reducing the amount of vector data transmitted and enabling a faster user response by receiving and restoring the compressed data from the server, and a program for realizing the same. The purpose is to provide a computer-readable recording medium.

1 is a block diagram of a client / server geographic information system to which the present invention is applied.

2 is a structural diagram of compressed data used in the present invention.

3 is a flowchart of an embodiment of a vector data compression method according to the present invention;

4 is a flowchart of an embodiment of a vector data recovery method according to the present invention;

* Explanation of symbols for the main parts of the drawings

10: Geographic Information System Server 11: Map Database

12: Property Database 13: User Application Client

According to an aspect of the present invention, there is provided a vector data compression and decompression method applied to a client / server geographic information system, wherein the planar rectangular coordinates of vector data are converted into relative screen coordinates in the server, and the converted relative screen In order to classify the vector data according to the vector data type by converting the coordinates into bits according to the characteristics of the vector data, the upper part of the X ("X") absolute value and the Y ("Y") absolute value is determined, and the separator bit and A first step of determining and storing consecutive bits and bits representing a number of sign bits and a number; And the client receives the reference absolute coordinates and the vector data from the server, and discriminates the delimiter bits and the consecutive bits of the compressed data according to the type of the vector data, and selects X ("X") from the bits representing the sign bits and the number. A first step of determining a range of absolute (" Y ") absolute values, determining and storing a separator bit, a continuous bit, and a bit representing a sign bit and a number; And the client receives the reference absolute coordinates and the vector data from the server, and discriminates the delimiter bits and the consecutive bits of the compressed data according to the type of the vector data, and selects X ("X") from the bits representing the sign bits and the number. And a second step of restoring the original data which is the Y ("Y") coordinate value.

The present invention also provides a vector data compression method applied to a client / server geographic information system, comprising: a first step of converting planar rectangular coordinates of vector data into relative screen coordinates in the server; And converting the changed relative screen coordinates into bits according to characteristics of the vector data to determine a range of an absolute value of X ("X") and an absolute value of Y ("Y") to classify the vector data according to the type of the vector data. And a second step of determining and storing the separator bit, the continuous bit, and the bit representing the sign bit and the number.

The present invention also provides a vector data restoration method applied to a client / server geographical information system, comprising: a first step of the client receiving reference absolute coordinates and vector data from the server; And discriminating the delimiter bits and the consecutive bits of the compressed data according to the type of the vector data, and restoring the original data which is an X ("X") and a Y ("Y") coordinate value from the bits representing the sign bit and the number. Characterized in that it comprises two steps.

On the other hand, in the present invention, a vector data compression and decompression system having a processor, the server converts the planar rectangular coordinates of the vector data into relative screen coordinates, and converts the converted relative screen coordinates into bits according to the characteristics of the vector data. To classify the vector data according to the type of the vector data, determine a range of X ("X") absolute value and Y ("Y") absolute value, and indicate delimiter bits, consecutive bits, sign bits and numbers. A first function of determining and storing bits; And the client receives the reference absolute coordinates and the vector data from the server, and discriminates the delimiter bits and the consecutive bits of the compressed data according to the type of the vector data, and selects X ("X") from the bits representing the sign bits and the number. A computer readable recording medium having recorded thereon a program for realizing a second function of restoring original data that is a Y ("Y") coordinate value is provided.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a client / server geographic information system to which the present invention is applied.

As shown in FIG. 1, a client / server geographic information system that handles an electronic map and attribute information related thereto according to an embodiment of the present invention may receive geographic information for receiving a map search request from a user application client 13 and transmitting vector data. The system server 10 and the user application client 13 which makes a map search request to the geographic information system server 10 and receives the result and outputs the result to the screen.

The geographic information system server 10 includes a database management system 102 for storing and managing a map database 11 and an attribute database 912, and a spatial database engine 101 mounted on the database management system 102 to retrieve vector data. It is provided.

The vector data of an electronic map is classified into spatial data types of points, lines, and faces, and is a set of absolute planar coordinate values constituting them, that is, {(X ₀ , X ₀ ), (X ₁ , Y ₁ ), { (X ₁ , Y ₁ ), (X ₂ , X ₂ ), ..., (X _n , Y _n )} (0 ?? n ?? Maximum number of points), but not displayed on the computer's monitor screen. In this case, the coordinates of the screen coordinate system must be converted and output.

In the client / server geographic information system to which the present invention is applied, the coordinate conversion process is performed by the geographic information system server 10 without performing the coordinate conversion process by the user application client 13 and monitors the user application client 13 necessary for this. The resolution is reported from the user application client 3 when the geographic information system server 10 connects to the user application client 913.

In general, the size of the data types representing and storing Number data are 2, 4, 8, and 16 bytes, but do not utilize all bits. That is, the actual number of bits required to store the integer N is "[log ₂ N + 1] + 1" including the Sign bit.

Therefore, the screen coordinate system has the resolution (640 ?? 480, 800 ?? 600, 1024 ?? 768, 1152 ?? 864, 1280 ?? 1024, 1600?) Of the monitor whose number range is the output device of the user application client 13. Suppose you do not deviate from? 1200), in order to represent (X _i , Y _i ) (1 ?? i ?? n), "[log ₂ (X total pixels) +1] + 1 + [log ₂ (Y Total pixels) +1] + 1 " bits. Here, assuming that the X coordinate is at least 0, at most 1600, and the Y coordinate is at least 0, at most 1200, at most "24 (11 + 1 + 11 + 1)" at least "4 (1 + 1 + 1 + 1)" bits. "I need a bit.

However, since the number of bits representing (X _i , Y _i ) is changed every time, a separate display method is required to classify and process them.

FIG. 2 is a structural diagram of compressed data used in the present invention, in which a total of five types including a flag bit and a next bit are fixed by fixing vector data storage units to 4 bits, 1 byte, and 2 bytes. Format exists.

Referring to Fig. 2, each of the relative screen coordinates X and Y is less than 1 byte unless it is less than ?? 3, one separator bit indicating "0", one negative sign bit, and two bits representing the number, respectively. Allocates X and Y to store (21).

If the relative screen coordinates X and Y both exceed ?? 3, and X or Y does not exceed ?? 32, one delimiter bit that indicates "1" is one byte or more, and there is no data consecutive to the next one byte. One continuous bit indicated by "0", one negative sign bit, and five bits representing a number are allocated to store X or Y (22).

On the other hand, if the relative screen coordinates X and Y both exceed ?? 3, and if X or Y exceeds ± 32 and does not exceed ± 2048, one delimiter bit that indicates that the first one byte is one or more bytes is 1, and then One consecutive bit to indicate that there is data contiguous in one byte, one negative sign bit, one separator bit to indicate that the next one byte is at least one byte, and a number representing a number. Allocate five upper bits, and one consecutive bit indicating "0" that there is no data consecutive to the next one byte, and six lower bits representing a number to store X or Y (23 to 25). ).

3 is a flowchart illustrating a vector data compression method according to the present invention, which illustrates a vector data compression procedure of an object transmitted from a server to a client.

As shown in FIG. 3, the vector data compression method according to the present invention first selects first coordinates (X, Y) from a coordinate group of vector data to be compressed (301).

If both the X and Y absolute values are less than hexadecimal "0x04" (?? X ?? <0x04 and ?? Y ?? <0x04) (302), the separator bit and the sign bit as shown in "21" of FIG. After determining the bit representing the number of and the number, and storing X in the upper 4 bits and Y in the lower 4 bits (303), it is checked whether the last coordinate of the object has been reached (312).

If both X absolute value and Y absolute value are greater than " 0x04 " and less than " 0x20 " (302,304), after storing X in the upper 8 bits and Y in the lower 8 bits as shown in " 22 " In operation 312, it is checked whether the last coordinate of the object has been reached.

If the X absolute value is greater than or equal to "0x20" and less than "0x800", and the Y absolute value is less than "0x20" (302,304,306), X is stored in the upper 16 bits and Y in the lower 8 bits as shown in "23" of FIG. Later (307), it is checked if the last coordinate of the object has been reached (312).

If the X absolute value is less than "0x20" and the Y absolute value is more than "0x20" and less than "0x80" (302,304,306,308), X is stored in the upper 8 bits and Y in the lower 16 bits as shown in "24" of FIG. Later (309), it is checked if the last coordinate of the object has been reached (312).

If both the X and Y absolute values are greater than or equal to '0x20' and less than "0x800" (302,304,306,308,310), after storing X in the upper 16 bits and Y in the lower 16 bits as shown in "25" of FIG. 2 (51) In operation 312, it is checked whether the last coordinate of the object has been reached.

As a result of the inspection, if the object is not the last coordinate, it moves to the next coordinate (313) and repeats steps 9302 to 311 until the last coordinate of the object is reached.

If both the X absolute value and the Y absolute value are greater than or equal to "0x800" (310), an error process is performed (314).

4 is a flowchart illustrating a method of recovering vector data according to an embodiment of the present invention.

As shown in FIG. 4, the vector data restoration method according to the present invention first selects the first 1 byte of the vector data to be restored (401), and analyzes the separator bit that is the first bit (402).

As a result of the analysis, if the separator bit is "0", the second bit is a sign and the third and fourth bits are converted into numbers, the X variable is converted into the X variable, the sixth bit is converted into a number, and the seventh and eighth bits are converted into numbers. After storing in a variable (9403), it is determined whether or not the final coordinate of the object (414).

As a result of the analysis, if the separator bit is "1", the continuous bit, which is the second bit, is checked (404).

As a result of the check, if the continuous bit is "0", the third bit is stored as a sign, the fourth to eighth bits as X (405), the pointer moves to the next byte (406), and then again at the moved position. A continuous bit, which is the second bit of the first 1 byte, is determined (409).

As a result of the check, if the consecutive bit is "1", the third bit is stored as X, which is the sign, the fourth through eighth bits, and the eleventh through sixteenth bits, and after moving the pointer after the next two bytes. (408), at the moved position, again determine the consecutive bits that are the second bits of the first one byte (409).

As a result of the determination, if the continuous bit is "0", the third bit is stored as a sign and the fourth to eighth bits as Y (410), and after moving the pointer to the next byte (411), it is the final coordinate of the object. Determine (414).

As a result of the determination, if the consecutive bit is "1", the third bit is stored as Y, which is a sign, the fourth through eighth bits, and the eleventh through sixteenth bits, and 412, and the pointer is moved after the next two bytes. In operation 413, it is determined whether the object is the final coordinate.

If it is determined that the final coordinates of the object are not (ie, the last byte has not been reached), the above steps 402 to 413 are repeated until the final coordinates are reached.

As described above, in the vector data compression and decompression method according to the present invention, various data compression ratios are calculated according to the distribution of the X and Y values of the vector data compressed by the compression algorithm, but the data amount of the raw data is large and dense There is a greater compression effect on vector data.

Particularly, in the present invention, if the relative screen coordinates in the relative screen coordinate system are all vector data within the range of ?? 3, the compression ratio is 8: 1, and the relative screen coordinates are all ?? If the vector data exists within the range of 31, the compression ratio is 4: 1. In addition, the present invention does not exceed the compression ratio 2: 1 even in the worst case, and the large-scale electronic map does not significantly affect the network transmission speed because the amount of vector data to be transmitted is small.

Therefore, the present invention can be applied to a S / W system based on a geographic information system (ie, vehicle control service, traffic information service, living geographic information service, etc.) in a client / server environment.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the spirit of the present invention for those skilled in the art to which the present invention pertains, and the above-described embodiments and accompanying It is not limited to the drawing.

As described above, the present invention can compress and decompress vector data in a geographic information system in a client / server environment, thereby reducing the amount of map data transmitted from the server to the client, reducing the transmission time, and solving user response delays. It has an effect.

Claims (7)

In the vector data compression and decompression method applied to a client / server geographic information system, The server converts the planar rectangular coordinates of the vector data into the relative screen coordinates, converts the converted relative screen coordinates into bits according to the characteristics of the vector data, and classifies the vector data according to the type of the vector data. A first step of determining a range of absolute values and Y ("Y") absolute values, and determining and storing a separator bit, a continuous bit, and a bit representing a sign bit and a number; And The client receives the reference absolute coordinates and the vector data from the server, and discriminates the delimiter bits and the consecutive bits of the compressed data according to the type of the vector data, so that X ("X"), Y Second step to restore the original data which is the ("Y") coordinate value Vector data compression and decompression method comprising a. The method of claim 1, The type of vector data is Units for storing vector data (XY) are fixed to 4 bits, 1 byte, and 2 bytes in X ("X") and Y ("Y") coordinates, respectively, so that the separator bit, the next bit, and the sign are fixed. Vector data compression and decompression method comprising five types including bits. The method of claim 1, The first step is, A third step of selecting first coordinates (X, Y) from a coordinate group of vector data to be compressed; For all object coordinates, if the absolute value of X ("X") and Y ("Y") are both less than hexadecimal "0x04", the delimiter bit, the sign bit, and the bit representing the number are determined to determine X ( A fourth step of storing "X") in the upper 4 bits and the Y ("Y") in the lower 4 bits; If both X ("X") and W ("Y") absolute values are greater than or equal to "0x04" and less than "0x20", then X ("X") is in the upper 8 bits and Y ("Y") is lower. A fifth step of storing in 8 bits; If X ("X") is greater than or equal to "0x20" and less than "0x800" and Y ("Y") is less than "0x20", then X ("X") is in the upper 16 bits and A sixth step of storing ") in the lower eight bits; If X ("X") is less than "0x20" and Y ("Y") is greater than "0x20" and less than "0x800", then X ("X") is in the upper 8 bits and Y ("Y"). A seventh step of storing &quot;) in the lower 16 bits; If both X ("X") and Y ("Y") absolute values are greater than or equal to "0x20" and less than "0x800", then X ("X") is in the upper 16 bits and Y ("Y") is lower. An eighth step of storing in 16 bits; And If the absolute value of X ("X") and the absolute value of "Y" are both "0x800" or more, the ninth step of error processing Vector data compression and decompression method comprising a. In the vector data compression method applied to client / server geographic information system, A first step of changing, from the server, planar rectangular coordinates of vector data into relative screen coordinates; And In order to classify the vector data according to the type of the vector data by converting the converted relative screen coordinates into bits according to the characteristics of the vector data, a range of an absolute value of X ("X") and a Y ("Y") is determined. And determining and storing the separator bit, the continuous bit, and the bit representing the sign bit and the number. Vector data compression method comprising a. A vector data restoration method applied to a client / server geographic information system, A first step of the client receiving reference absolute coordinates and vector data from the server; And A second bit for discriminating delimiter bits and contiguous bits of the compressed data according to the type of vector data, and restoring the original data as X ("X") and Y ("Y") coordinate values from the bits representing the sign bit and the number; step Vector data restoration method including The method of claim 1, The second step, Selecting a first day (" 1 ") byte of vector data to be restored; A fourth step of analyzing, for all object coordinates, a separator bit that is a first bit; As a result of the analysis of the fourth step, if the separator bit is zero ("0"), the second bit is a sign and the third and fourth bits are converted into numbers to sign the X ("X") variable and the sixth bit is a sign. A fifth step of converting the seventh and eighth bits into numbers and storing them in a Y ("Y") variable; A sixth step of checking a continuous bit as the second bit if the separator bit is one ("1") as a result of the analysis of the fourth step; As a result of the check in the sixth step, if the continuous bit is zero ("0"), the third bit is stored as a sign, and the fourth to eighth bits are numbers X ("X"), and the pointer is moved to the next byte. Later, a seventh step of determining the contiguous bit which is the second bit of the first one ("1") byte again in the moved position; As a result of the check in the sixth step, if the consecutive bits are one ("1"), the third bit is suited as X ("X") which is a number, followed by the fourth to eighth bits and the eleventh to sixteenth bits. An eighth step of, after moving the pointer behind the next two ("2") bytes, determining a contiguous bit that is the second bit of the first one ("1") byte again at the moved position; As a result of the determination in the seventh and eighth steps, if the continuous bit is zero ("0"), the third bit is stored as a sign ("Y") with the number and the fourth to eighth bits as numbers, and the pointer is stored as the next byte. A ninth step of moving; And As a result of the determination of the seventh and eighth steps, if the consecutive bits are one (" 1 "), the wise number " Y " is the number, followed by the fourth to eighth bits and the eleventh to sixteenth bits. The tenth step to save as ") and move the pointer behind the next two (" 2) bytes Vector data recovery method comprising a. In a vector data compression and decompression system with a processor, The server converts the planar rectangular coordinates of the vector data into the relative screen coordinates, converts the converted relative screen coordinates into bits according to the characteristics of the vector data, and classifies the vector data according to the type of the vector data. A first function of determining a range of absolute values and absolute ("Y") absolute values, and determining and storing a separator bit, a continuous bit, and a bit representing a sign bit and a number; And The client receives the reference absolute sin and vector data from the server, and discriminates the delimiter bits and the consecutive bits of the compressed data according to the type of the vector data, and selects X ("X"), Y from the bits representing the sign bit and the number. Second function to restore the original data which is the ("Y") coordinate value Vector data compression and decompression method comprising a.