关键词：ArcObject，ArcGIS，栅格像元值（遥感图像）读取，样带，Excel，Matlab。 遥感影像以缩微的形式记录地表特征，已被广泛应用于区域土地覆被变化等研究当中。每幅遥感数据都是一个数据矩阵，这与很多科学软件的数据格式有共同之处（如Matlab、Excel）。任何专业软件都有其突出的有点和明显的缺陷，一般的遥感处理软件（如ERDAS或ENVI）都是针对栅格数据的，或实现矢量数据的一般功能。所以，不同软件之间高精度数据迁移转换是日常科研当中的重要任务。本文以NDVI为例，基于ArcObject＋VBA在ArcGIS环境中编写程序，生成NDVI样带数据序列，为日后在Matlab中进行数据分析调定基础。 背景：时间序列数据分析在地理学研究当中是一种常用的地理过程研究方法，GIS以其强大的能力能够有效处理空间问题，把GIS与时间序列分析方法相结合，根据其共性发展出一种空间序列分析方法。在空间序列方法中，以空间位置代表时间位置，而空间位置上的属性变量的表达方式与时间序列相一致。其实，空间序列方法有其地理学的传统名词样带。 需求分析：提取NDVI影像上的数据样带NDVI值，生成一维空间序列数据，使其能在EXCEL或Matlab中进行数据分析。 代码思路： 1）用线数据集Clip影像，生成样带数据，数据中只有线数据集覆盖下的范围融合NDVI值； 2）循环计算栅格影像各行数据，当像元值大于0时则记录该值，否则跳过。（AO的PixelBlock每128行跳过一次）； 3）将记录好的数据保存在txt中。（Excel和Matlab支持文本数据导入。） 实现代码： ' Part 1: Define the temporary raster data. Dim pMxDoc As IMxDocument Dim pMap As IMap Dim pRasterLy As IRasterLayer Dim pRaster As IRaster Dim pRasBandC As IRasterBandCollection Dim pRasterDS As IRasterDataset Set pMxDoc = ThisDocument Set pMap = pMxDoc.FocusMap ' Get the raster from the raster layer. Set pRasterLy = pMap.Layer(0) Set pRaster = pRasterLy.Raster ' Set the raster dataset to be the first band of the raster Set pRasBandC = pRaster Set pRasterDS = pRasBandC.Item(0).RasterDataset Dim pRasterCursor As IRasterCursor Dim pRaster1 As IRaster2 Set pRaster1 = pRasterDS.CreateDefaultRaster Set pRasterCursor = pRaster1.CreateCursorEx(Nothing) 'use IRasterEdit interface Dim pRasterEdit As IRasterEdit Set pRasterEdit = pRaster1 'loop through each pixel block in the raster. Dim pPB As IPixelBlock3 Dim PixelBlockWidth As Long, PixelBlockHeight As Long ' Dim pTLC As IPnt Dim pBandCol As IRasterBandCollection Set pBandCol = pRasterDS ''''''''''''''' Dim v As Double Dim i As Integer Dim j As Integer Dim length As Integer length = 0 Dim VAL1(2890) As Double '1990=2959 这里要实现计算样带中的非零值个数 '2000=2961 '2005=2890 Do Set pPB = pRasterCursor.PixelBlock For i = 0 To pPB.Width - 1 For j = 0 To pPB.Height - 1 v = pPB.GetVal(0, i, j) If v 0 Then 如果像元值不为零，则存入数据集中 VAL1(length) = v length = 1 + length End If Next j Next i Loop While pRasterCursor.Next = True MsgBox length ' Dim l As Integer l = length Open c:\ndvi05.txt For Output As #1 记入文本 For i = 0 To l - 1 Step 1 Print #1, , VAL1(i); Next i Close #1 ' End Sub 相关截图： 1）ArcGIS图示效果 2）Excel数据显示（其中一段） 3）Matlab中显示效果（整个数据样带） 原文于新浪博客 2010-10-21
NITF is abbrevation of National Imagery Transmission Format, whihc is a raster format standard defined by NITF Standards Technical Board. Geospatial analysts in different industries use NITF to store multiple types of data in a single file, including imagery, vectors, annotation, and complex metadata. The NITF format allows for storage and disseminaiton of imaginery and its associated metadata - or the detailed information about the location, context, context, and structure of the image - in a single file. NITF is essential to the interoperability of systems within and among many government organizations worldwde. Further, to ensure proper usage and implementation across systems and customers accessing the NITF data format, the Joint Interoperability Test Command (JITC) certifies systems implementing the NITF format for compliance with the standard. The NITF is the standard for formatting digital imagery and imagery-related products and exchanging them among members of the Intelligence Community (IC), the Department of Defence (DOD), and other departments and agencies of the United States Government as governed by Memoranda of Agreement (MOA) with those departments and agencies. The initial NITFS purpose was to standardize the imagery format and associated data being transmitted from/to secondary imagery dissemination (SIDS). Due to the growing NITFS acceptance, it is now being applied to imagery dissemination systems in general, not SIDS alone. The purpose of NITFS is to transmit a file composed of an image accompnied by subimages, symbols, labels, text, and other information that relate to the image. One of the main features of NITFS is that it allows several items of each data type to be included in one file, yet any data types may be omitted. The NITF file incorporates the CGM standard for graphic and accommodates user-selectable compression for images. The file is submitted to the Message Transfer Facility (MXF), which allows it to be transferred usiing any of a set of user-selectable protocols and media. The output is a message which, by conforming to the standards and their use, is compliant with NITFS.
标签: ArcGIS
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