DEM拼接的问题

<P>DD</P>
<P>我有几个临近地区的DEM文件，请问各位大侠用什么软件把它们拼接成一个DEM文件，如何拼接啊？</P>

<P>creates one grid from two or more adjacent grids and makes a smooth transition over the overlapping areas of the neighboring grids.</P>
<P>MOSAIC(<grid, ..., grid>) </P>
<P>Arguments</P>
<P><grid, ..., grid> - names of the spatially neighboring grids which are to be put into a mosaic. </P>
<P>Notes</P>
<P> The MOSAIC function can be very useful when a set of adjacent grids needs to be merged into one entity but also when it is desired to minimize  the abrupt changes along the boundaries of the overlapping grids. </P>
<P> MOSAIC is designed primarily for the continuous data. That is, due to the nature of mosaicing, the appropriate results over the overlapping areas can be expected only for the continuous type of data, such as the spatially adjacent grids representing Digital Elevation Models, satellite images acquired in a slightly different time, containment plumes, etc.</P>
<P> Both, integer and floating point type of grids can be entered as input into MOSAIC. The output grid will be a floating point grid unless all of the member grids are of the integer type. </P>
<P> For the floating point input grids of different resolution it is recommended to RESAMPLE all the data using BILINEAR interpolation or CUBIC convolution before running MOSAIC. Otherwise, the MOSAIC function will automatically resample the grids using NEAREST neighbor (which is not appropriate for the continuous type of data) and the current cell size setting in GRID environment and then perform mosaicing. The default cell size is set to the MAXOF. With that unchanged, the function will resample the finer grid(s) to the coarsest resolution. </P>
<P> The maximum number of grids that can be opened simultaneously in GRID is 50. Therefore, the maximum number of grids entered into the MOSAIC function is restricted to 49 (which includes 49 input grids and 1 output grid), 48 if a mask grid has been identified, 1024 characters (including commas) on the input string, and the number of files that the Operating System which can open at a time.</P>
<P> Valid expressions include:</P>
<P>biggrid = mosaic( ingrid1, ingrid2, ingrid3 )</P>
<P>Discussion</P>
<P>The MOSAIC function works similarly to the MERGE function. When the grids to be put together do not have any overlapping area, there is no difference in the output from both functions. The difference is the processing of the overlapping areas. In case of MERGE, the sequence of input grids determines the values assigned to cells over the common map extent, giving  priority to those entered first.</P>
<P>For MOSAIC, the sequence of entry on the command line is irrelevant if on each overlapping area no more than two grids intersect. MOSAIC uses a weighted average method to calculate values of cells in the overlapping area, taking input from two or more input grids. The proximity analysis algorithm applied to determine cell values over the overlapping areas is called the Hermite Cubic and can be described by the following formula:</P>
<P>where, s is the normalized distance (ranging values from 0 to 1) of the width of the overlapping area (it may be oriented horizontally or vertically). The cell values for the output C grid, being the mosaic of grids A and B (see left diagram below) on the overlapping area (marked x on the diagram) are calculated according to this formula:</P>
<P>The right diagram above shows graphically how the applied weighted average method works on the overlapping area. The ratio of weights of the overlapping grids changes within the width (s) of the x area. </P>
<P>Examples</P>
<P>For the purpose of explanation, each one of the two grids used in the following example represents a discrete type of data which in general is not applicable for mosaicing. The input grids have different map extents, one is shifted versus the other for one column, with the five columns being common for both. The one called 搃ngrid2?is a floating point grid while the other one is an integer. </P>
<P>If the input grids are of the integer type of data, the output grid would also be integer and the values of the output grid would be truncated.</P>
<P>The MOSAIC function itself will not interpolate to fill missing data which may happen while putting a set of grids into one composite entity. The following GRID expression may help to solve the problem by interpolating values of the missing cells. It will fill gaps of up to three rows or columns of NODATA cells (the length of the gap is unrelated) with the mean cell value of the 4 x 4 square, leaving the valid existing data unchanged. If the gap is wider than 3 cells, the size of the focal window may be very conservatively increased.</P>
<P>Grid: final_mosaic = con(isnull(gap_mosaic), focalmean(gap_mosaic, rectangle,4,4), gap_mosaic) </P>
<P>References</P>
<P>Franke, R. (1982). Smooth Interpolation of Scattered Data by Local Thin Plate Splines. Comp. ; Maths with Appls. Vol. 8, No. 4, pp. 273 - 281. Pergamon Press Ltd. </P>

<P>水平有限，还看不大明白，支持一下！</P><img src="images/post/smile/dvbbs/em01.gif" /><img src="images/post/smile/dvbbs/em02.gif" /><img src="images/post/smile/dvbbs/em05.gif" />

用GLOBALMAPPER软件

我用的是ArcGIS9.1，方法是ArcTool——>Data Managment Tools——>Raster——>Mosaic To New Raster工具.

<P>必须是9.1么？9.0可以么？</P><img src="images/post/smile/dvbbs/em01.gif" /><img src="images/post/smile/dvbbs/em02.gif" />

GRID下用MERGE可以合并。

<P>为什么我在执行Mosaic To New Raster时总是出错呢？</P>
<P>提示信息如下：</P>
<P>Executing (MosaicToNewRaster_8): MosaicToNewRaster C:\aa\2.bil;C:\aa\3.bil C:\aa 4.bil # 32_BIT_UNSIGNED # 1 FIRST REJECT C:\aa\4.bil<BR>Start Time: Tue Oct 17 09:59:23 2006<BR>Executing (Create Raster Dataset): CreateRasterDataset C:\aa 4.bil # 32_BIT_UNSIGNED # 1 # "PYRAMIDS -1 NEAREST" "128 128" LZ77 # C:\aa\4.bil<BR>Start Time: Tue Oct 17 09:59:23 2006<BR>Error in executing function<BR>Failed to execute (Create Raster Dataset).<BR>End Time: Tue Oct 17 09:59:23 2006 (Elapsed Time: 0.00 secs)<BR>Failed to execute (MosaicToNewRaster_8).<BR>End Time: Tue Oct 17 09:59:23 2006 (Elapsed Time: 0.00 secs)<BR></P>
<P>哪位高人帮看一下，谢谢啦！</P>

<P>研究了好久，有了一点进展，处理的数据可能必须是grid格式才行，而且转化成grid格式后，再使用Mosaic To New Raster，依然会有一个错误，如下：</P>
<P>Executing (MosaicToNewRaster_15): MosaicToNewRaster C:\test\calc26;C:\test\calc27 C:\aa 147 12.5 32_BIT_UNSIGNED # 1 FIRST REJECT C:\aa\147<BR>Start Time: Wed Oct 18 15:38:17 2006<BR>Executing (Create Raster Dataset): CreateRasterDataset C:\aa 147 12.5 32_BIT_UNSIGNED # 1 # "PYRAMIDS -1 NEAREST" "128 128" LZ77 # C:\aa\147<BR>Start Time: Wed Oct 18 15:38:17 2006<BR>Executed (Create Raster Dataset) successfully.<BR>End Time: Wed Oct 18 15:38:17 2006 (Elapsed Time: 0.00 secs)<BR>Executing (Mosaic): Mosaic C:\test\calc26;C:\test\calc27 C:\aa\147 FIRST REJECT # # NONE 0 C:\aa\147<BR>Start Time: Wed Oct 18 15:38:18 2006<BR>("esriDataSourcesRaster.RasterDataset") Failed to rename the specified file<BR>Failed to execute (Mosaic).<BR>End Time: Wed Oct 18 15:38:20 2006 (Elapsed Time: 2.00 secs)<BR>Failed to execute (MosaicToNewRaster_15).<BR>End Time: Wed Oct 18 15:38:20 2006 (Elapsed Time: 3.00 secs)<BR></P>
<P>原因可能是数据名称有问题，换用了字母开头的数据名称，问题就解决了</P>
<P>一点小技巧，和大家分享一下</P>

学习<img src="images/post/smile/dvbbs/em01.gif" />