CADRG(压缩弧数字化光栅图形)阅读器/作家
Licensing optionsfor this format begin with FME Professional Edition.
FME可以在CADRG(压缩弧数字化光栅图形)格式中读取和写入数据。
概述
CADRG是一种通用产品,包括计算机可读数字地图和图表图像。它支持各种武器,C3I剧院战役管理,使命规划和数字移动地图系统。CADRG数据通过DOWN采样,过滤,压缩和重新格式化为栅格产品格式(RPF)标准来源于ADRG和其他数字源。
CADRG文件通常在国家图像传输格式(NITF)消息中物理格式化。CADRG读取器可以读取有或没有NITF消息包装器的CADRG文件。CADRG Writer可以创建带有或不带NITF消息包装器的CADRG数据集。这些选项可在Writer功能类型参数中提供。
The CADRG reader and writer implement the following standards:
- MIL-C-89038
- MIL-STD-2411
- MIL-STD-2411-1
- MIL-STD-2411-2
CADRG image data is of appropriate size and quality for use in military command and control systems, ground-based force to unit-level mission planning systems, and aircraft cockpit “moving map” displays. The post-reduction filtering scheme emphasizes legibility of text and contour lines to ensure that displayed and printed digital maps are readable and distinct. CADRG is intended to satisfy the needs of a broad range of users in its compression ratio, display and print quality and displayed screen size.
The CADRG datasets shall conform to MIL-STD-2411. It normally will be produced directly from source maps of all scales by processing and re-formatting into a CADRG frame file structure. Miscellaneous scale maps and charts or non-DMA maps may be the source for CADRG production. The processing includes spatial reduction (pixel downsampling) with filtering, vector quantization image compression, and color quantization.
为了允许飞机驾驶舱显示器直接使用,CADRG数据布置在具有恒定像素大小的帧和子帧中,并且与航空电子计算机的有限存储器和处理能力一致的重叠。
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在CADRG中,投影系统是弧形。如MIL-A-89007中所述,电弧系统将地球椭圆体的表面分成18个纬度带称为区域。区域1-9覆盖北半球和区域10-18(A至J,CADRG中的I A到J,Cadrg)覆盖南半球。每个半球的一个区域覆盖了极地区域。每个非极性区域覆盖两个纬度限制之间的椭圆体的一部分,并且完全环绕地球。CADRG的基准应为WGS-84,如DMA TM 8358.1所定义。CADRG中的经度和纬度的WGS-84坐标在-180度<= +180度和-90度<=纬度<= +90度的范围内签名值。
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CADRG数据集由每个区域的像素帧的矩形网格组成。CADRG可以分布在矩形或非矩形区域,以及连续或非连续覆盖范围。每个帧由离散文件表示。CADRG库是无缝的;也就是说,除了由原始源图形中的颜色或图案之间的差异是凹陷的,除了颜色变化之外,连续源映射的边缘是难以区分的。
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CADRG数据文件位于分层文件夹/子文件夹结构中。文件夹的所有名称和标签以及文件夹的格式和结构应遵循MIL-STD-2411中规定的约定。根文件夹包含一个目录文件表(a.toc),一个或多个帧文件文件夹,图例文件夹和一个或多个概述图像。目前,在任何情况下都没有使用图例文件夹和概述图像。
The ARC system divides the surfaces of the earth ellipsoid into 18 latitudinal bands called zones. The CADRG database is composed of rectangular grids of frames of pixels for each zone. Each frame is represented by a discrete file, and the data files are arranged in a hierarchical folder/subfolder structure. The location and name of each file are recorded in a CADRG Table of Contents (TOC) file in the root folder.
TOC文件提供了分发媒体的数据内容的概述。它将路径名存储给每个帧文件。CADRG生产者将在给定数据集中的框架文件文件夹中选择将帧文件分配给文件夹的框架文件文件夹数。给定数据集上的每个帧文件文件夹应以授权生产者确定的方式唯一命名。使用变量层次结构,生产者还可以根据需要分配嵌套帧文件文件夹以组织帧文件。FME中的CADRG Writer为每个数据序列代码创建一个唯一的帧文件文件夹,如下面的属性部分所述。帧文件包含CADRG数据集上的地理帧的瓷砖图像和支持数据。框架文件命名约定应符合MIL-STD-2411。
For each map or chart scale, which can be adjusted with the data series attribute, a constant latitudinal (row) and longitudinal (column) pixel interval shall exist in each zone.
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每个帧应包括1536的矩形阵列,乘1536像素(2,359,296像素)。每个帧应将每个帧铺在6乘6个子帧(36个子帧)的网格中。每个子帧应包括256的矩形阵列256输出像素(65,536像素)。区域内的所有帧和子帧应以互斥的方式邻接,无需任何像素重叠或像素冗余。区域的北部和南部边界通常不会落在框架或子帧的北部和南部边界上。区域之间应框架重叠。
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框架文件内部的实体的编号公约应符合MIL-STD-2411。所有索引号应从帧文件子项中的帧,像素和索引中的行和列的行开始。应从0中计算。帧内帧和子帧中的子帧和像素编号的原点应为左上角。子帧和像素应以来自原点的行主要顺序计数。另外,可以认为CADRG帧在区域内形成概念行和列。该概念用于通过使用比例和区域特定帧编号来定义各种尺度的帧的命名惯例。行和列的编号为0.计算北部和南半球的非极性帧行和列的起源是该区域的南部最纬度,180度的西部经度,柱子以东方方向计算来自原点。计数偏光帧的原点是极性区域的左下角,具有从该原点编号的行和列。
对于非极性区域,由于在向外纬度的伸展处伸展并且在东西方向上的赤道纬度处缩小,存在一些视觉变形。在每个区域的中纬度下,没有沿着所选平行的失真。由于区域之间包含重叠的整个帧文件,因此对于非常小的刻度图(例如,GNC,JNC),重叠区域中可能存在显着的视觉失真。对于大多数尺度,极性区域的失真小于10%。
The CADRG format itself allows updates/replacements of frame files. However, the current versions of CADRG Reader and Writer in FME do not support CADRG updates/replacements.
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在压缩过程中,源数据中的可用颜色应从1670万可能颜色的调色板量化到CADRG帧文件中最多216种颜色。量化颜色应在带有216个条目的LUT中定义。为透明像素保留217个条目。
提供额外的颜色表中of the 216 colors in the primary color table is mapped to a color in the reduced color table through use of a color conversion table. Standard CADRG data sets will include 216, 32, and 16 entry color tables. Each color entry contains 4 bytes. The first byte contains the red intensity level, the second byte contains the green intensity level, the third byte contains the blue intensity level, and the fourth byte contains a monochrome (grayscale) intensity level, which is an arithmetic combination of red, green and blue intensity levels. The equation used to calculate the monochrome intensity level is: 0.299 (Red) + 0.587 (Green) + 0.114 (Blue). The 216 or 217 entries in the color table contain RGB and monochrome values in the range 0 - 255. The entries in the color table represent RGBM values for pixels in the digitized map that represent RGBM values for pixels in the digitized map that represent digitized map data. Entry 216 is reserved for “transparent” pixels, for cases where the data is missing or not available at the given geographic location. The RGBM values in the CADRG color table for the 217th entry (index 216, for transparent pixels) are 0, 0, 0, 0.
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Spatial compression shall be performed using a Vector Quantization (VQ) algorithm that employs a 4 x 4 compression kernel size with 4096 codebook entries.
读者概述
FME considers a single CADRG TOC file to be a dataset.
CADRG TOC文件包含帧文件的位置和名称。帧文件是包含像素数据的栅格文件。
Writer Overview
FME认为CADRG目标数据集是容器文件夹名称。每个特征类型都有一个容器文件夹内的子文件夹。在每个子文件夹中,有一个目录文件A.TOCand one or more subfolders containing some frame files. The frame files and their subfolders are named according to the specification MIL-STD-2411.
All raster features of the same CADRG feature type are grouped under one table of contents file. Each raster feature represents one boundary rectangle, but when the extents of the raster feature overlap two or more zones, the raster feature will be broken down into multiple boundary rectangles, each of which covers the raster subset in one zone. According to the specification, adjacent zones overlap each other, and the raster data in the intersection area will be repeated in the two boundary rectangles. Since each zone has a specific vertical/horizontal intervals and resolutions, the boundary rectangles may need to be resampled.
每个边界矩形将被分解为一个或多个帧文件。每个帧文件的大小为1536 x 1536.当帧中的行数或列数小于4时,写入器不会创建帧文件,因为编写器需要至少4行和列进行空间压缩。当栅格具有Nodata值或217,33和17条目时,三个调色板分别有216,32和16个条目分别当栅格具有Nodata值时。每个调色板条目是一个四字节的RGBM。第一个字节R包含红色强度级别,第二个字节G包含绿色强度级别,第三个字节B包含蓝色强度级别,第四个字节M包含单色(灰度)强度级别,这是红色的算术组合,绿色和蓝色强度水平。用于计算单色强度水平的等式是:0.299(红色)+ 0.587(绿色)+ 0.114(蓝色)。
在调色板中,最后一个条目(分别为217,33和第17条条目)保留用于Nodata值,或者“透明”像素,或者在给定的地理位丢失或不可用的情况下的“透明”像素。Nodata条目的CADRG调色板中的RGBM值为0,0,0,0。
FME栅格特色
FME raster features represent raster data and use several concepts that are unlike those used in the handling of vector data. See关于FME Rasters.。
The CADRG reader produces rasters with a single UInt8 band that has multiple palettes.
CADRG作家只接受带有RED8频段,绿色8频段和蓝色8频段的栅格。