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When point cloud data is collected,将各种组件分配给每个单独的点,包括坐标,intensity,and classification.在创建曲面模型时,使用点分类可以快速轻松地识别地面点,从而从中提取曲面模型。In the examples below we will demonstrate how a custom transformer called thePointCloudLASClassifiercreated by a 亚搏在线Safe Software team member can be used within a 亚搏在线workflow to create a DEM or TIN model.
The custom transformer PointCloudLASClassifier can be used to increase the accuracy of a DEM or TIN output by extracting just the ground points.If the point cloud data that you are working with does not have a classification component,then using shapefiles to remove non-ground points,像建筑物一样,can be used.Thisarticleexplains how to this can be done.
要沿点云边缘生成正确的高程,all adjacent point cloud tiles must be taken into account.However,generating a single digital elevation model (DEM) for the center tile and all adjacent tiles can significantly affect performance.为了减少整体数据量,we can generate a relatively small buffer around the central point cloud tile and clip the edges of the adjacent tiles with this buffer.The resulting point cloud (the center tile with the edges of adjacent tiles) will be used for making a DEM raster,and then the raster can be clipped to the original extents of the center tile.
a.b.
Image a.shows the original point cloud data with the central tile of interest selected.Image b.is the resulting DEM output from the LAS to DEM 亚搏在线workflow below.
DEM是代表地球表面的常用模型。They are raster based models with cell values representing different levels of elevation.由于每个单元是表面积高程的平均表示,natural landscapes appear smooth,while man-made landscapes appear rough.使用FME从LAS数据创建DEM快速简单,因为您只能使用地面分类点来创建模型。
The points within a point cloud have a component called classification.组件中代码的值表示类建筑物或地面。为了创建DEM,我们只需要地面类。The steps for creating a DEM from a point cloud are as follows:
Optional: Try running the workspace without the link from the PointCloudLASClassifier transformer to the RasterDEMGenerator and instead connect the "Split" points from the PointCloudSplitter.Compare the different output DEMs.
a.b.
Image a.shows the what the DEM output looks like when all points are used in the 亚搏在线workflow to create a DEM.Image b.Is what the DEM looks like when only the ground classified points are used.Using only the ground classified points creates a much smoother and realistic representation of the ground itself.
如果使用其他LAS文件生成DEM,检查这些点是否带有分类。If so,确保只使用适当的类来生成DEM。
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当点云具有分类组件时,可以实现用建筑物创建曲面模型的最佳结果。We can use the Data Inspector orPointCloudPropertyExtractor以检查此组件是否存在。If the point cloud has a classification of 2,地面,it is often enough for generating surface.However,excluding buildings can still help to make a more precise model as it can help avoid classification errors.Thisarticleexplains more about splitting points cloud by class.此工作区的步骤如下:
The output from this workspace is much smoother.Note that the bridges have disappeared from the model.This means that they have some other classification rather than ground:
This workspace generates a TIN (as a 3D PDF file) using a DEM as a texture:
hi Mita
I triedLAS_to_Textured_TIN_FME2011.fmwtand it gave me blank PDF after 14 minutes running.what am i missing here?can u advise please.
海卡尔It's hard to say without looking at your data/workspace.Note that the workspace is reading in tiles and then doing some processing on them in the workspace.Are you also reading tiles?Does the log report any errors/warnings?We have a debugging guide that should helphttps://knowledge.亚搏在线safe.com/articles/19301/root-cause-analysis-guide.html
你好
I tried your las to DEM and I got "Translation was SUCCESSFUL with 1 warning(s) (0 feature(s) output)
FME Session Duration: 24 minutes 52.7 seconds.(CPU: 1489.6s user,1.1s system)
END - ProcessID: 5428,峰值进程内存使用率:1322008 KB,current process memory usage: 50552 kB
Translation was SUCCESSFUL"
However,我无法显示结果,Any advice?
regards
Please find attached my *.fmw filemita-las-to-dem.fmw
I appreciate any advice and recommendation
Hi海卡尔The log is saying you have "0 features output".There are transformers in your workspace that need to be connected,and also that don't have their properties set.I suggest removing everything but the RasterDEMGenerator and see if that works,至少。If you are still having problems please send along your workspace and source data to our support teamhttps://support.亚搏在线safe.com/knowledgeSubmitCase
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