CN108830929A - Multi-resolution Terrain pyramid model generation method and system based on database - Google Patents
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Abstract
本发明公开了一种基于数据库的多分辨率地形金字塔模型生成方法及系统,通过数据获取—模型生成—数据入库这三个步骤,对现有金字塔模型方法进行了大幅度的改进,大大减少数据搜寻定位的时间和I/O次数,使得数据可共享,提高了渲染绘制速度;同时将模型数据按照预设规则存入数据库中,可以降低数据的冗余量,减少数据预处理及存储时间,提高漫游响应速度。
The invention discloses a method and system for generating a multi-resolution terrain pyramid model based on a database. Through the three steps of data acquisition-model generation-data storage, the existing pyramid model method is greatly improved, greatly reducing The time of data search and positioning and the number of I/O times make the data shareable and improve the rendering speed; at the same time, the model data is stored in the database according to the preset rules, which can reduce data redundancy and reduce data preprocessing and storage time , to improve roaming response speed.
Description
技术领域technical field
本发明涉及三维GIS领域,尤其涉及一种基于数据库的多分辨率地形金字塔模型生成方法及系统。The invention relates to the field of three-dimensional GIS, in particular to a method and system for generating a multi-resolution terrain pyramid model based on a database.
背景技术Background technique
三维地形可视化是一项涉及计算机图形学、多媒体学以及地理信息科学这三门学科领域的应用技术,它是对一定区域范围内的地形数据进行多分辨率组织、建模和渲染的过程。目前,大规模三维地形可视化技术在各个领域都被广泛应用。例如,军事模拟作战系统、3D游戏、街景导航、城市规划等。3D terrain visualization is an application technology involving computer graphics, multimedia and geographic information science. It is a process of multi-resolution organization, modeling and rendering of terrain data within a certain area. At present, large-scale 3D terrain visualization technology is widely used in various fields. For example, military simulated combat systems, 3D games, street view navigation, urban planning, etc.
随着计算机图形学、计算机图形硬件技术以及计算机存储硬件水平的不断发展,计算机仿真与可视化技术日益成熟,这也为三维地形可视化技术的深入发展赋予了新的动力。但即使这样,对于数据量多达GB甚至TB数量级的大规模地形数据,无论是在数据的组织存储上,还是在数据的计算调度上,都会给三维地形的实时渲染带来极大的挑战。With the continuous development of computer graphics, computer graphics hardware technology and computer storage hardware level, computer simulation and visualization technology is becoming more and more mature, which also gives new impetus to the in-depth development of 3D terrain visualization technology. But even so, for large-scale terrain data of the order of GB or even TB, it will bring great challenges to the real-time rendering of 3D terrain, whether it is in the organization and storage of data or in the calculation and scheduling of data.
现有技术中,构建多分辨率地形金字塔模型的方法是以DEM(Digital ElevationModel,数字高程模型)数据为出发点,但其没有考虑计算机渲染设备的能力,且其对于原始数据的宽高尺寸有硬性要求,即宽高尺寸必须为2 N ×2 N ,但实际的某地域的原始数据宽高尺寸不可能刚好满足要求。同时,地形数据的存储方式主要是基于文件或文件夹,该方式需要建立很多的文件或文件夹,并且其数据组织结构不紧凑、索引编号繁杂,数据更新缓慢,不支持网络环境下的多用户操作。In the prior art, the method of constructing a multi-resolution terrain pyramid model is based on DEM (Digital Elevation Model, digital elevation model) data, but it does not consider the ability of computer rendering equipment, and it has rigidity for the width and height of the original data Requirements, that is, the width and height dimensions must be 2 N × 2 N , but the width and height dimensions of the original data in a certain region cannot just meet the requirements. At the same time, the storage method of terrain data is mainly based on files or folders. This method needs to create a lot of files or folders, and its data organization structure is not compact, the index number is complicated, the data update is slow, and it does not support multi-users in the network environment. operate.
因而,结合目前三维地形可视化的迅猛发展,立足于我国现状,设计一个可操作的且经济有效的方法,对三维GIS领域的发展意义重大。Therefore, in combination with the rapid development of 3D terrain visualization and based on the current situation of our country, designing an operable and cost-effective method is of great significance to the development of 3D GIS field.
发明内容Contents of the invention
本发明正是针对现有技术中大数据高存储对当下三维地形的实时渲染带来的挑战,提供了一种基于数据库的多分辨率地形金字塔模型生成方法及系统,通过数据获取—模型生成—数据入库这三个步骤,对现有金字塔模型方法进行了大幅度的改进,大大减少数据搜寻定位的时间和I/O次数,使得数据可共享,提高了渲染绘制速度;同时将模型数据按照预设规则存入数据库中,可以降低数据的冗余量,减少数据预处理及存储时间,提高漫游响应速度。The present invention is aimed at the challenges brought by the high storage of big data to the real-time rendering of the current 3D terrain in the prior art, and provides a method and system for generating a multi-resolution terrain pyramid model based on a database. Through data acquisition-model generation- The three steps of data warehousing have greatly improved the existing pyramid model method, greatly reducing the time of data search and positioning and the number of I/O times, making the data shareable and improving the rendering speed; at the same time, the model data is Preset rules are stored in the database, which can reduce data redundancy, reduce data preprocessing and storage time, and improve roaming response speed.
为了实现上述目的,本发明采用的技术方案是:基于数据库的多分辨率地形金字塔模型生成方法,包括如下步骤:In order to achieve the above object, the technical solution adopted in the present invention is: a method for generating a multi-resolution terrain pyramid model based on a database, comprising the steps of:
S1,获取原始地形数据并进行格式转换,获得DEM数据和DOM数据;S1, obtain the original terrain data and perform format conversion to obtain DEM data and DOM data;
S2,根据显存限制利用S1中获取的DEM数据和DOM数据分别生成多分辨率DEM金字塔模型和多分辨率DOM金字塔模型;S2, using the DEM data and DOM data obtained in S1 to generate a multi-resolution DEM pyramid model and a multi-resolution DOM pyramid model respectively according to the video memory limitation;
S3,将所述多分辨率DEM金字塔模型的数据和多分辨率DOM金字塔模型的数据按预设规则存入数据库中。S3, storing the data of the multi-resolution DEM pyramid model and the multi-resolution DOM pyramid model into the database according to preset rules.
作为本发明的一种改进,所述步骤S2包括:As an improvement of the present invention, the step S2 includes:
S21,读取DEM数据和DOM数据;S21, reading DEM data and DOM data;
S22,根据S21中获取的DEM数据和DOM数据确定多分辨率DEM金字塔模型和多分辨率DOM金字塔模型的模型层数;S22, determining the number of model layers of the multi-resolution DEM pyramid model and the multi-resolution DOM pyramid model according to the DEM data and DOM data obtained in S21;
S23,根据所述模型层数和显存限制分别确定所述DEM数据和DOM数据的地形分块大小;S23. Determine the terrain block size of the DEM data and the DOM data respectively according to the number of model layers and the video memory limit;
S24,对所述DEM数据和DOM数据进行无效数据填充处理;S24, performing invalid data filling processing on the DEM data and DOM data;
S25, 根据S23中地形分块大小分别对S24无效数据填充处理后的DEM数据和DOM数据进行分块;S25, the DEM data and the DOM data after S24 invalid data filling processing are respectively divided into blocks according to the terrain block size in S23;
S26,计算出每一DEM分块的粗糙度数值;S26, calculating the roughness value of each DEM block;
S27,对分块后的DEM数据和DOM数据采用双线性插值法进行重采样,生成上一层数据;S27, resampling the DEM data and DOM data after block by bilinear interpolation method to generate upper layer data;
S28,重复步骤S25至S27,直到达到S22中多分辨率DEM金字塔模型和多分辨率DOM金字塔模型的模型层数。S28, repeat steps S25 to S27, until the number of model layers of the multi-resolution DEM pyramid model and the multi-resolution DOM pyramid model in S22 is reached.
作为本发明的一种改进,所述步骤S22中,根据如下公式计算出DOM数据中包含的DEM分块个数k:As an improvement of the present invention, in the step S22, the number k of DEM blocks contained in the DOM data is calculated according to the following formula:
k=max(RasterXSize,RasterYSize)/(max(col,row)-1);k=max(RasterXSize, RasterYSize)/(max(col, row)-1);
其中,max(RasterXSize,RasterYSize) 为DOM数据宽度和高度两者中的较大值,max(col,row)为DEM数据中行和列两者中的较大值;Among them, max(RasterXSize, RasterYSize) is the larger value of DOM data width and height, and max(col, row) is the larger value of row and column in DEM data;
根据如下公式计算多分辨率DEM金字塔模型和多分辨率DOM金字塔模型的模型层数n:The number of model layers n of the multi-resolution DEM pyramid model and the multi-resolution DOM pyramid model is calculated according to the following formula:
k×2n∈[512,1024],计算出最小正整数n。k×2 n ∈ [512, 1024], calculate the smallest positive integer n.
作为本发明的另一种改进,所述步骤S23中,根据如下公式计算DEM分块大小:As another improvement of the present invention, in the step S23, the DEM block size is calculated according to the following formula:
(2n+1)×(2n+1);( 2n +1)×( 2n +1);
根据显存支持的最佳单张影像大小,利用如下公式计算DOM分块大小:According to the optimal single image size supported by video memory, use the following formula to calculate the DOM block size:
max(RasterXSize,RasterYSize)/(max(col,row)-1)×2n max(RasterXSize, RasterYSize)/(max(col, row)-1)×2 n
其中,max(RasterXSize,RasterYSize) 为DOM数据宽度和高度两者中的较大值,max(col,row)为DEM数据中行和列两者中的较大值,n为多分辨率DEM金字塔模型和多分辨率DOM金字塔模型的模型层数。Among them, max(RasterXSize, RasterYSize) is the larger value of DOM data width and height, max(col, row) is the larger value of row and column in DEM data, and n is the multi-resolution DEM pyramid model and the number of model layers for the multi-resolution DOM pyramid model.
作为本发明的另一种改进,所述步骤S24包括:以原始地形数据左上角为原点,对所述原始地形数据进行无效数据填充处理,使得DEM数据的行和列均为2N+1,DOM数据的宽和高均为2N,其中,N为能使填充后的数据刚好包围所述原始地形数据的最小正整数。As another improvement of the present invention, the step S24 includes: taking the upper left corner of the original terrain data as the origin, performing invalid data filling processing on the original terrain data, so that the rows and columns of the DEM data are both 2 N + 1, The width and height of the DOM data are both 2 N , where N is the smallest positive integer that enables the filled data to just surround the original terrain data.
作为本发明的又一种改进,所述步骤S26中,提前计算出地形粗糙度数值并存入数据库中,每一DEM分块的粗糙度数值根据如下公式计算:As another improvement of the present invention, in the step S26, the terrain roughness value is calculated in advance and stored in the database, and the roughness value of each DEM block is calculated according to the following formula:
其中,d为DEM分块的边长,e 1~e 6为地形块节点的6个顶点误差值,e 7~e 10为地形块节点的4个子节点误差值。Among them, d is the side length of the DEM block, e 1 ~ e 6 are the error values of the 6 vertices of the terrain block node, and e 7 ~ e 10 are the error values of the 4 child nodes of the terrain block node.
作为本发明的又一种改进,所述步骤S27中对进行无效数据填充处理且分块后的原始地形数据再进行每2×2个数据块的重采样,若每2×2个数据块中既包括原始地形数据,又包括无效填充数据,则将所述无效填充数据改为数值0,再进行重采样计算;若每2×2个数据块中只包括无效填充数据,则不进行重采样计算。As another improvement of the present invention, in the step S27, resampling of every 2×2 data blocks is performed on the original terrain data after the invalid data filling process and block, if every 2×2 data blocks If both original terrain data and invalid filling data are included, the invalid filling data is changed to a value of 0, and then resampling calculation is performed; if only invalid filling data is included in each 2×2 data block, resampling is not performed calculate.
作为本发明的更进一步改进,所述步骤S3包括:As a further improvement of the present invention, the step S3 includes:
S31,根据地形分块的坐标及其在金字塔模型中的层数,计算出多分辨率DEM金字塔模型中每一DEM分块的索引编号和多分辨率DOM金字塔模型中每一DOM分块的索引编号,将所述索引编号作为主键索引;S31, calculate the index number of each DEM block in the multi-resolution DEM pyramid model and the index number of each DOM block in the multi-resolution DOM pyramid model according to the coordinates of the terrain block and the number of layers in the pyramid model number, using the index number as the primary key index;
S32,在数据库中创建一个项目,并在项目中建立多分辨率DEM金字塔模型数据表和多分辨率DOM金字塔模型数据表;S32, creating a project in the database, and establishing a multi-resolution DEM pyramid model data table and a multi-resolution DOM pyramid model data table in the project;
S33,将所述多分辨率DEM金字塔模型的数据和多分辨率DOM金字塔模型的数据以二进制BLOB的形式分别存入多分辨率DEM金字塔模型数据表和多分辨率DOM金字塔模型数据表。S33. Store the data of the multi-resolution DEM pyramid model and the multi-resolution DOM pyramid model in the form of binary BLOB into the multi-resolution DEM pyramid model data table and the multi-resolution DOM pyramid model data table respectively.
作为本发明的更进一步改进,所述步骤S33中,将每一DEM分块的边界数据在多分辨率DEM金字塔模型数据表中重复存储,在所述多分辨率DOM金字塔模型数据表中增加一行记录,用于存储DOM数据的原始尺寸信息及分块大小信息。As a further improvement of the present invention, in the step S33, the boundary data of each DEM block is repeatedly stored in the multi-resolution DEM pyramid model data table, and one row is added in the multi-resolution DOM pyramid model data table Record, used to store the original size information and block size information of DOM data.
为了实现上述目的,本发明还采用了一种技术方案是:基于数据库的多分辨率地形金字塔模型生成系统,包括:In order to achieve the above object, the present invention also adopts a kind of technical scheme is: the multi-resolution terrain pyramid model generation system based on database, comprising:
数据获取模块:获取原始地形数据并进行格式转换,获得DEM数据和DOM数据;Data acquisition module: acquire the original terrain data and perform format conversion to obtain DEM data and DOM data;
模型生成模块:根据显存限制,利用数据获取模块中获得的DEM数据和DOM数据分别生成多分辨率DEM金字塔模型和多分辨率DOM金字塔模型;Model generation module: according to the memory limit, use the DEM data and DOM data obtained in the data acquisition module to generate a multi-resolution DEM pyramid model and a multi-resolution DOM pyramid model respectively;
数据入库模块:将多分辨率DEM金字塔模型的数据和多分辨率DOM金字塔模型的数据按预设规则存入数据库中。Data storage module: store the data of the multi-resolution DEM pyramid model and the multi-resolution DOM pyramid model into the database according to preset rules.
与现有技术相比,本发明的有益效果是:本发明摒弃了传统的文件存储方式,采用了数据库的存储方式,可以大大减少数据搜寻定位的时间和I/O次数,并使得数据可共享;模型的建立考虑显存的显示性能,可以充分利用计算机硬件的性能,提高渲染绘制速度;将模型数据按照预设规则存入数据库中,可以降低数据的冗余量,减少数据预处理及存储时间,提高漫游响应速度。Compared with the prior art, the beneficial effect of the present invention is that the present invention abandons the traditional file storage method and adopts the database storage method, which can greatly reduce the time of data search and location and the number of I/O times, and make the data shareable ;The establishment of the model considers the display performance of the video memory, which can make full use of the performance of the computer hardware and improve the rendering speed; store the model data in the database according to the preset rules, which can reduce the redundancy of data, reduce the time of data preprocessing and storage , to improve roaming response speed.
附图说明Description of drawings
图1为本发明实施例提供的基于数据库的多分辨率地形金字塔模型生成方法流程图;Fig. 1 is the database-based multi-resolution terrain pyramid model generation method flowchart that the embodiment of the present invention provides;
图2为本发明实施例中地形粗糙度的确定示意图;Fig. 2 is the determination schematic diagram of terrain roughness in the embodiment of the present invention;
图3为本发明实施例中DEM边界数据存储原则示意图;Fig. 3 is the schematic diagram of DEM border data storage principle in the embodiment of the present invention;
图4为本发明实施例提供的基于数据库的多分辨率地形金字塔模型生成系统框图。FIG. 4 is a block diagram of a database-based multi-resolution terrain pyramid model generation system provided by an embodiment of the present invention.
具体实施方式Detailed ways
以下将结合附图和实施例,对本发明进行较为详细的说明。The present invention will be described in detail below with reference to the accompanying drawings and embodiments.
实施例1Example 1
一种基于数据库的多分辨率地形金字塔模型生成方法,如图1所示,包括如下步骤:A database-based multi-resolution terrain pyramid model generation method, as shown in Figure 1, comprises the following steps:
S1,获取原始地形数据并进行格式转换,获得DEM数据和DOM数据;可以从LocalSpaceViewer上下载需要进行三维可视化操作的原始地形数据,并使用ArcMap软件中ArcToolbox转换工具的【Raster to ASCII】功能,将下载的TIFF(Tag Image File Format,标签图像文件格式)格式的地形高程数据文件转为规则格网DEM数据;DOM(DigitalOrthophoto Map,数字正射影像)数据则保持下载时的TIFF格式不变。S1. Obtain the original terrain data and perform format conversion to obtain DEM data and DOM data; you can download the original terrain data that needs to be visualized in 3D from LocalSpaceViewer, and use the [Raster to ASCII] function of the ArcToolbox conversion tool in the ArcMap software to convert The downloaded topographic elevation data file in TIFF (Tag Image File Format, tag image file format) format is converted into regular grid DEM data; DOM (Digital Orthophoto Map, digital orthophoto) data remains in the same TIFF format when downloaded.
需要说明的是,规则格网DEM数据一般是以.asc作为后缀的文本文件,其包含有6行头信息和若干行高程数据值。头信息中,ncols和nrows分别表示规则格网地形数据的列数、行数,xllcorner和yllcorner表示的是栅格的左下角角点的坐标,cellsize是指像元大小,也即每个格网单元的尺寸,NODATA_value表示无效数据,其余的是相应坐标的高程数据。It should be noted that the regular grid DEM data is generally a text file with the suffix .asc, which contains 6 lines of header information and several lines of elevation data values. In the header information, ncols and nrows represent the number of columns and rows of regular grid terrain data respectively, xllcorner and yllcorner represent the coordinates of the lower left corner of the grid, and cellsize refers to the size of the cell, that is, each grid The size of the unit, NODATA_value means invalid data, and the rest is the elevation data of the corresponding coordinates.
S2,根据显存限制利用S1中获取的DEM数据和DOM数据分别生成多分辨率DEM金字塔模型和多分辨率DOM金字塔模型;S2, using the DEM data and DOM data obtained in S1 to generate a multi-resolution DEM pyramid model and a multi-resolution DOM pyramid model respectively according to the video memory limitation;
S3,将所述多分辨率DEM金字塔模型的数据和多分辨率DOM金字塔模型的数据按预设规则存入数据库中,可选用Oracle数据库,将多分辨率DEM金字塔模型的数据和多分辨率DOM金字塔模型的数据按预设规则存入Oracle数据库中,方便快捷。S3, storing the data of the multi-resolution DEM pyramid model and the data of the multi-resolution DOM pyramid model in the database according to the preset rules, the Oracle database can be selected, and the data of the multi-resolution DEM pyramid model and the multi-resolution DOM The data of the pyramid model is stored in the Oracle database according to the preset rules, which is convenient and quick.
实施例2Example 2
本实施例与实施例1不同之处在于:步骤S2包括:The difference between this embodiment and Embodiment 1 is that step S2 includes:
S21,读取DEM数据和DOM数据,如DEM数据行列数、DOM影像尺寸等。对于规则格网DEM数据,获取DEM数据中行和列两者中的较大值max(col,row)。对于DOM数据,借助GDAL(Geospatial Data Abstraction Library,空间数据转换库)函数,获取DOM数据宽度和高度两者中的较大值max(RasterXSize,RasterYSize)。S21, reading DEM data and DOM data, such as the number of rows and columns of DEM data, DOM image size, etc. For regular grid DEM data, obtain the larger value max(col, row) of both rows and columns in the DEM data. For DOM data, use the GDAL (Geospatial Data Abstraction Library, spatial data conversion library) function to obtain the larger value max(RasterXSize, RasterYSize) of the width and height of the DOM data.
S22,根据S21中获取的DEM数据和DOM数据确定多分辨率DEM金字塔模型和多分辨率DOM金字塔模型的模型层数;由公式k=max(RasterXSize,RasterYSize)/(max(col,row)-1)计算出DOM数据中可包含的DEM分块个数。以显存支持的最佳单张影像大小为前提,即条件k×2 n ∈[512,1024],计算出最小正整数n,得到多分辨率金字塔层数n。S22, determine the number of model layers of the multi-resolution DEM pyramid model and the multi-resolution DOM pyramid model according to the DEM data and DOM data obtained in S21; by formula k = max(RasterXSize, RasterYSize) / (max(col, row)- 1 ) Calculate the number of DEM blocks that can be included in the DOM data. On the premise of the best single image size supported by video memory, that is, the condition k× 2 n ∈ [512, 1024], the minimum positive integer n is calculated to obtain the number of multi-resolution pyramid layers n .
S23,根据所述模型层数和显存限制分别确定所述DEM数据和DOM数据的地形分块大小,根据如下公式计算DEM分块大小;S23. Determine the terrain block size of the DEM data and the DOM data respectively according to the number of model layers and the video memory limit, and calculate the DEM block size according to the following formula;
(2n+1)×(2n+1);( 2n +1)×( 2n +1);
根据显存支持的最佳单张影像大小,利用如下公式计算DOM分块大小;According to the optimal single image size supported by video memory, use the following formula to calculate the DOM block size;
max(RasterXSize,RasterYSize)/(max(col,row)-1)×2n。max(RasterXSize, RasterYSize)/(max(col, row)-1)×2 n .
由于是从显存支持的最佳单张影像大小及DEM和DOM数据范围的对应关系出发来计算DEM分块及DOM分块的大小,可保证对任意尺寸的原始地形数据来说,充分考虑计算机硬件的性能,可充分发挥显存的渲染绘制性能,渲染绘制均非常流畅,若显存支持的最佳单张影像范围发生变化,也只需在程序中修改定义的常量值即可。同时,金字塔模型的层数不需在程序中提前设定,也不需要对金子模型数据中最顶层数据的尺寸进行限制。该种计算方式,可以自由控制金字塔的分层层数及最顶层金字塔模型数据的尺寸(不一定非要为2n×2n)。Since the size of the DEM block and DOM block is calculated based on the optimal single image size supported by the video memory and the corresponding relationship between the DEM and DOM data ranges, it can ensure that the computer hardware is fully considered for the original terrain data of any size. It can give full play to the rendering and drawing performance of the video memory, and the rendering and drawing are very smooth. If the optimal single image range supported by the video memory changes, it is only necessary to modify the defined constant value in the program. At the same time, the number of layers of the pyramid model does not need to be set in advance in the program, nor does it need to limit the size of the topmost data in the golden model data. This calculation method can freely control the number of hierarchical layers of the pyramid and the size of the top pyramid model data (not necessarily 2 n × 2 n ).
S24,对所述DEM数据和DOM数据进行无效数据填充处理,如果不进行无效数据填充处理,对于边界数据,在进行分块操作时,若其大小不满足每一分块大小要求,则对不满足要求的地形块,还要计算其应该增加几行几列数据以及这些数据的位置,不利于地形分块的进行。该实施例中,对原始数据进行无效数据填充,可加速地形分块的过程,避免在边界处重复计算。S24, perform invalid data filling processing on the DEM data and DOM data, if the invalid data filling processing is not performed, for the boundary data, if the size does not meet the size requirements of each block when performing the block operation, then For terrain blocks that meet the requirements, it is necessary to calculate how many rows and columns of data should be added and the location of these data, which is not conducive to the terrain block. In this embodiment, padding the original data with invalid data can speed up the terrain block process and avoid repeated calculations at boundaries.
以原始地形数据左上角为原点,对所述原始地形数据进行无效数据填充处理,使得DEM数据的行和列均为2N+1,DOM数据的宽和高均为2N,其中,N为能使填充后的数据刚好包围所述原始地形数据的最小正整数。Taking the upper left corner of the original terrain data as the origin, the original terrain data is filled with invalid data, so that the rows and columns of the DEM data are both 2 N + 1, and the width and height of the DOM data are both 2 N , where N is The smallest positive integer that can make the filled data just surround the original terrain data.
这样可以定义无效数据-9999对所述原始地形数据进行无效数据填充处理,使其大小满足要求。In this way, the invalid data-9999 can be defined to fill the original terrain data with invalid data so that its size meets the requirement.
S25, 根据S23中地形分块大小分别对S24无效数据填充处理后的DEM数据和DOM数据进行分块;S25, the DEM data and the DOM data after S24 invalid data filling processing are respectively divided into blocks according to the terrain block size in S23;
S26,计算出每一DEM分块的粗糙度数值;提前计算出地形数据的粗糙度数据,可以降低在数据调度过程中所需地形数据层次确定的耗时以及计算地形三角网绘制中地形细分程度的耗时。S26, calculate the roughness value of each DEM block; calculate the roughness data of the terrain data in advance, which can reduce the time-consuming determination of the required terrain data level in the data scheduling process and calculate the terrain subdivision in the terrain triangulation drawing degree of time-consuming.
如图2所示,可根据如下公式计算出每一DEM分块的粗糙度数值;As shown in Figure 2, the roughness value of each DEM block can be calculated according to the following formula;
其中,d为DEM分块的边长,e 1~e 6为地形块节点的6个顶点误差值,e 7~e 10为地形块节点的4个子节点误差值。Among them, d is the side length of the DEM block, e 1 ~ e 6 are the error values of the 6 vertices of the terrain block node, and e 7 ~ e 10 are the error values of the 4 child nodes of the terrain block node.
S27,对分块后的DEM数据和DOM数据采用双线性插值法进行重采样,生成上一层数据;S27, resampling the DEM data and DOM data after block by bilinear interpolation method to generate upper layer data;
常规的地形金字塔生成方式是:DEM数据隔行隔列采样,DOM数据进行三次卷积法采样。这种方式由于DEM数据和DOM数据的采样方式不同,会使地形可视化过程中进行纹理映射操作时,影像纹理(DOM)发生拉伸现象,地形可视化效果质量低,仿真效果不真实。同时,三次卷积法虽然精度高,有增强边缘的功能,但其缺点是计算量较大,速度较慢,对大规模地形数据来说使用该方法进行采样耗时过多。本实施例中,采用双线性插值法进行重采样,其精度和计算量适中,并自带低通滤波功效,重采样后的图像边缘比较平滑,具有平均化的滤波效果。DEM数据和DOM数据均使用双线性插值法,这样其在数据变化的规律上是一致的,进行纹理映射操作时,不会发生纹理拉伸现象。The conventional terrain pyramid generation method is: DEM data is sampled every other row and column, and DOM data is sampled by three times convolution method. Due to the different sampling methods of DEM data and DOM data in this method, the image texture (DOM) will be stretched when the texture mapping operation is performed during the terrain visualization process, the quality of the terrain visualization effect is low, and the simulation effect is unreal. At the same time, although the cubic convolution method has high precision and has the function of enhancing the edge, its disadvantages are that the calculation amount is large and the speed is slow, and it takes too much time to use this method to sample large-scale terrain data. In this embodiment, the bilinear interpolation method is used for resampling, which has moderate accuracy and calculation amount, and has its own low-pass filtering function. The edge of the resampled image is relatively smooth and has an average filtering effect. Both DEM data and DOM data use bilinear interpolation, so that they are consistent in the law of data change, and texture stretching will not occur during texture mapping operations.
本步骤中的重采样过程,还涉及到对原始地形数据边缘处无效数据的重定义:对进行无效数据填充处理且分块后的原始地形数据进行每2×2个数据块的重采样,若每2×2个数据块中既包括原始地形数据,又包括无效填充数据,则将所述无效填充数据改为数值0,再进行重采样计算;若每2×2个数据块中只包括无效填充数据,则不进行重采样计算。The resampling process in this step also involves the redefinition of invalid data at the edge of the original terrain data: the original terrain data that has been filled with invalid data and divided into blocks is resampled every 2×2 data blocks, if Each 2×2 data block includes both original terrain data and invalid filling data, then change the invalid filling data to a value of 0, and then perform resampling calculation; if each 2×2 data block only includes invalid If the data is filled, no resampling calculation is performed.
这样就没有直接定义无效数据值为0,而是首先定义无效数据值为-9999,再修改为0,是为了避免在地形边缘数据中存在大量0值的情况下,无法准确确定出原始地形的范围,而增加过多冗余数据。In this way, the invalid data value is not directly defined as 0, but the invalid data value is firstly defined as -9999, and then changed to 0, in order to avoid the inability to accurately determine the original terrain when there are a large number of 0 values in the terrain edge data range, while adding too much redundant data.
S28,重复步骤S25至S27,直到达到S22中多分辨率DEM金字塔模型和多分辨率DOM金字塔模型的模型层数。S28, repeat steps S25 to S27, until the number of model layers of the multi-resolution DEM pyramid model and the multi-resolution DOM pyramid model in S22 is reached.
实施例3Example 3
本实施例与实施例1的不同之处在于:步骤S3进一步包括:The difference between this embodiment and Embodiment 1 is that step S3 further includes:
S31,根据地形分块的坐标及其在金字塔模型中的层数,计算出多分辨率DEM金字塔模型中每一DEM分块的索引编号和多分辨率DOM金字塔模型中每一DOM分块数据的索引编号,将所述索引编号作为主键索引;S31, according to the coordinates of the terrain block and the number of layers in the pyramid model, calculate the index number of each DEM block in the multi-resolution DEM pyramid model and the data of each DOM block in the multi-resolution DOM pyramid model An index number, using the index number as a primary key index;
根据公式ID=ix*total_row+iy*total*col+lev计算出多分辨率金字塔模型中每一DEM分块数据和DOM分块数据的索引编号;其中,ix、iy为当前地形块的横纵坐标,total_row、total_col分别为整块原始数据的行列数,lev为当前地形块所处的分辨率层次。Calculate the index number of each DEM block data and DOM block data in the multi-resolution pyramid model according to the formula ID =ix*total_row+iy*total*col+lev ; among them, ix and iy are the horizontal and vertical of the current terrain block Coordinates, total_row and total_col are the number of rows and columns of the entire original data, and lev is the resolution level of the current terrain block.
本实施例中,编号的获得充分使用了数据的所有信息。使得在知道地形分块的编号及行列号的情况下,可以计算出其在地形块在金字塔模型中所处的层号。比如,对于行和列位置相同的不同层数据,根据编号值,就可以知道其层号。In this embodiment, all the information of the data is fully used in obtaining the serial number. This makes it possible to calculate the layer number of the terrain block in the pyramid model when the number and row number of the terrain block are known. For example, for different layers of data with the same row and column position, the layer number can be known according to the number value.
S32,在数据库中创建一个项目,并在所述项目中建立多分辨率DEM金字塔模型数据表和多分辨率DOM金字塔模型数据表;S32, creating a project in the database, and establishing a multi-resolution DEM pyramid model data table and a multi-resolution DOM pyramid model data table in the project;
本实施例使用Oracle数据库,在数据库中创建一个项目,并在所述项目中建立多分辨率DEM金字塔模型数据表和多分辨率DOM金字塔模型数据表。将得到的多分辨率DEM金字塔模型的数据和多分辨率DOM金字塔模型的数据按一定规则存入Oarcle数据库中,同时设置地形块编号为主键索引,可以降低数据的冗余量,减少数据预处理及存储时间,提高场景漫游时的响应速度。In this embodiment, an Oracle database is used to create a project in the database, and a multi-resolution DEM pyramid model data table and a multi-resolution DOM pyramid model data table are established in the project. Store the obtained multi-resolution DEM pyramid model data and multi-resolution DOM pyramid model data in the Oarcle database according to certain rules, and set the terrain block number as the primary key index at the same time, which can reduce data redundancy and data preprocessing and storage time, improving the response speed when roaming the scene.
S33,将所述多分辨率DEM金字塔模型的数据和多分辨率DOM金字塔模型的数据以二进制BLOB的形式分别存入多分辨率DEM金字塔模型数据表和多分辨率DOM金字塔模型数据表。S33. Store the data of the multi-resolution DEM pyramid model and the multi-resolution DOM pyramid model in the form of binary BLOB into the multi-resolution DEM pyramid model data table and the multi-resolution DOM pyramid model data table respectively.
在本实施例中,名为GEO_DATA的表(即多分辨率DEM金字塔模型数据表),用于存储多分辨率DEM金字塔模型数据,列名为GEO_ID,LEV,GEO,NORMAL,分别用来存储DEM金字塔模型数据的索引ID,层次级别lev,高程值和地形粗糙度数值;同时,对于DEM数据,由于其数据量远小于DOM的数据量,所以,对于每一DEM分块的边界数据,在数据库中重复存储,如图3所示。In this embodiment, the table named GEO_DATA (that is, the multi-resolution DEM pyramid model data table) is used to store multi-resolution DEM pyramid model data, and the column names are GEO_ID, LEV, GEO, and NORMAL, which are used to store DEM respectively Pyramid model data index ID, hierarchical level lev , elevation value and terrain roughness value; at the same time, for DEM data, because its data volume is much smaller than DOM data volume, so, for the boundary data of each DEM block, in the database In repeated storage, as shown in Figure 3.
名为TIFF_DATA的表(即多分辨率DOM金字塔模型数据表),用于存储多分辨率DOM金字塔模型数据,列名为TIFF_ID,LEV,TIFF,分别用来存储DOM金字塔模型数据的索引ID,层次级别lev,影像RGB值;同时,在此表中增加一行记录,用于存储DOM数据的原始尺寸信息及分块大小信息。The table named TIFF_DATA (that is, the multi-resolution DOM pyramid model data table) is used to store the multi-resolution DOM pyramid model data, and the column names are TIFF_ID, LEV, TIFF, which are used to store the index ID and level of the DOM pyramid model data respectively Level lev , the RGB value of the image; at the same time, add a row to this table to store the original size information and block size information of the DOM data.
使用Oracle数据库的OCI(Oracle Call Interface,Oracle接口调用),将模型数据以二进制BLOB的形式分别存入多分辨率DEM金字塔模型数据表和多分辨率DOM金字塔模型数据表,可加速数据存取过程。Use the OCI (Oracle Call Interface) of the Oracle database to store the model data in the form of binary BLOB into the multi-resolution DEM pyramid model data table and the multi-resolution DOM pyramid model data table respectively, which can speed up the data access process .
在数据入库过程中,对于DEM数据,由于其数据量远小于DOM数据量,因此,对于每一DEM分块的边界数据,在数据库中重复存储。而对于DOM数据,其数据格式为TIFF,该格式的文件虽然画质高,但其压缩率低,占的内存多。为了避免存储大量的无效数据,本发明在存储多分辨率DOM金字塔模型数据的表中增加一行记录,用于存储DOM数据的原始尺寸信息及分块大小信息,以便于后续在调度DOM边界数据时,程序可以根据前一列或上一行的信息计算出边界数据的轮廓信息。In the process of data storage, for DEM data, since its data volume is much smaller than that of DOM data, the boundary data of each DEM block is repeatedly stored in the database. As for DOM data, its data format is TIFF. Although the file quality of this format is high, its compression rate is low and it takes up a lot of memory. In order to avoid storing a large amount of invalid data, the present invention adds a row of records in the table for storing multi-resolution DOM pyramid model data, which is used to store the original size information and block size information of DOM data, so that when scheduling DOM boundary data in the future , the program can calculate the contour information of the boundary data according to the information of the previous column or row.
实施例4Example 4
基于数据库的多分辨率地形金字塔模型生成系统,包括数据获取模块、模型生成模块和数据入库模块。A multi-resolution terrain pyramid model generation system based on a database, including a data acquisition module, a model generation module and a data storage module.
数据获取模块用来获取原始地形数据并进行格式转换,获得DEM数据和DOM数据;模型生成模块用来根据显存限制利用所述DEM数据和DOM数据分别生成多分辨率DEM金字塔模型和多分辨率DOM金字塔模型;数据入库模块将所述多分辨率DEM金字塔模型的数据和多分辨率DOM金字塔模型的数据按预设规则存入数据库中。The data acquisition module is used to obtain the original terrain data and perform format conversion to obtain DEM data and DOM data; the model generation module is used to generate a multi-resolution DEM pyramid model and a multi-resolution DOM by using the DEM data and DOM data according to the memory limit Pyramid model; the data storage module stores the data of the multi-resolution DEM pyramid model and the multi-resolution DOM pyramid model into the database according to preset rules.
上述实施例中,解决了现有方式适用性窄,数据冗余量大,数据搜寻定位时间长的技术问题。采用了数据库的存储方式,可以大大减少数据搜寻定位的时间和I/O次数,并使得数据可共享;模型的建立考虑显存的显示性能,可以适用于任意大小范围的地形数据,充分利用计算机硬件的性能,提高渲染绘制速度;将模型数据按照预设规则存入数据库中,可以降低数据的冗余量,减少数据预处理及存储时间,提高漫游响应速度。In the foregoing embodiments, the technical problems of narrow applicability, large data redundancy, and long time for data search and location are solved in the existing methods. The storage method of the database is used, which can greatly reduce the time of data search and positioning and the number of I/O, and make the data shareable; the establishment of the model considers the display performance of the video memory, and can be applied to terrain data of any size range, making full use of computer hardware The performance of the model improves the rendering and drawing speed; the model data is stored in the database according to the preset rules, which can reduce data redundancy, reduce data preprocessing and storage time, and improve roaming response speed.
以上显示和描述了本发明的基本原理、主要特征和本发明的优点。本行业的技术人员应该了解,本发明不受上述实例的限制,上述实例和说明书中描述的只是说明本发明的原理,在不脱离本发明精神和范围的前提下本发明还会有各种变化和改进,这些变化和改进都落入要求保护的本发明范围内。本发明要求保护范围由所附的权利要求书及其等同物界定。The basic principles, main features and advantages of the present invention have been shown and described above. Those skilled in the industry should understand that the present invention is not limited by the above-mentioned examples. What are described in the above-mentioned examples and descriptions are only to illustrate the principles of the present invention. The present invention also has various changes without departing from the spirit and scope of the present invention. These changes and improvements all fall within the scope of the claimed invention. The protection scope of the present invention is defined by the appended claims and their equivalents.
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