使用lidar360和arcgis生成DEM渲染图

将原始点云数据生成漂亮的dem的过程：

1、首先使用lidar360软件加载原始点云数据，使用地形分类工具完成地面点提取，也就是滤波操作，完成之后，将提取的地面点生成dem并以tif格式保存。

2、将lidar360软件生成的dem数据在Arcmap当中加载并打开。使用search直接搜索hillshade功能，

需要设置的除了设置输入输出路径和文件名，还需要设置两个参数：一个是altitude太阳高度角（0-90，默认值是45，早上和下午低，正午最高），一个是azimuth方位角（0-360，默认值是315，表示光照来自西北方向）。网上搜索得到北京夏天正午的日照效果参数是225和90 。我试着设置成135和45，上午的照射方向，效果也不错。

Z factor的意思是夸张程度，这个值可以适当改大，更能突出效果，我在生成的时候设置的是5。

3、生成hillshade之后将其放到图层的最下方，在下图的图层管理模式下可以自由拖动图层排列层次。

4、剩下的就是设置dem的colorbar和调节相关的参数使得显示效果更佳。

选择如上图所示的colorbar效果较好，使用的stretch类型可根据实际情况进行选择和实验，esri官方给出的介绍：

Stretch types

The stretch type defines a histogram stretch that will be applied to the rasters to enhance their appearance. The stretch types include Minimum-Maximum, Standard Deviation, Percent Clip, and None. Stretching improves the appearance of the data by spreading the pixel values along a histogram from the minimum and maximum values defined by their bit depth. For example, an 8-bit raster dataset or mosaic dataset will be stretched from 0 to 255. Different stretches will produce different results in the raster display.

Below shows an example of a stretch: Histogram A represents the pixel values in image A. By stretching the values (shown in histogram B) across the entire range, you can alter and visually enhance the appearance of the image (image B).

Minimum-Maximum

This stretch type applies a linear stretch based on the output minimum and output maximum pixel values, which are used as the endpoints for the histogram. For example, in an 8-bit dataset, the minimum and maximum values could be 33 and 206. A linear stretch is used to distribute the values across 256 values, from 0 to 255. Features in the imagery are easier to distinguish as the pixel values are distributed across the entire histogram range, brightening and increasing the contrast of the image.

Standard Deviation or Percent Clip

In many cases, you can assume that the majority of the pixel values fall within an upper and lower limit. Therefore, it's reasonable to trim off the extreme values. You can do this statistically by defining either a standard deviation or clipping percent. The Standard Deviation stretch type applies a linear stretch between the values defined by the standard deviation (n) value. The Percent Clip stretch type applies a linear stretch between the percent clip minimum and percent clip maximum pixel values defined.

When you use either of these stretch types, all the values in the histogram falling outside the values defined will be pushed to the ends. For example: Your histogram has the same range of values as above, 33 to 206, and you've defined a percent clip minimum and maximum of 2. If 2 percent at the low end is values 33 to 45 and 2 percent at the high end is 198 to 206, the histogram will be redistributed to spread the values from 0 to 255, all values 33 to 45 becoming 0 and 198 to 206 becoming 255, with all others spread in between. Similarly, if you define a 2 standard deviation, then the values beyond the 2nd standard deviation become 0 or 255 and the remaining values are stretch in between 0 to 255.

5、继续设置图层属性的display效果：

通过对比度、亮度、透明度的设置来对比效果。

这里我使用的是对比度10和透明度30的设置。

最终效果：

参考资源：

http://resources.arcgis.com/en/help/main/10.1/index.html#//009t00000059000000；

http://www.orz520.com/a/doc/2014/0911/2025527.html?from=haosou；