Important

翻译是一项社区工作:ref:你可以加入<translation_guidelines>。此页面目前翻译进度为 74.42%。

8.2. 课程：结合分析

使用栅格分析的矢量化结果将允许您仅选择适合地形上的建筑。

本课目标: 使用矢量化地形结果选择合适的地块。

8.2.1. ★★☆ 自己试试：

1. 保存当前地图 (raster_analysis.qgs) 。

2. 打开之前在矢量分析期间创建的地图 (您应该将文件保存为 analysis.qgs) 。

3. 在 图层 面板，启用以下图层：

   • hillshade,

   • solution (or buildings_over_100)

4. 除了这些图层之外 (应该在您之前处理地图时已经加载到地图中)，还需要添加 suitable_terrain.shp 数据集。

5. 如果缺少某些图层，您应该在 exercise_data/residential_development/ 中找到它们。

6. Use the Intersection tool (Vector ► Geoprocessing Tools) to create a new vector layer called new_solution.shp which contains only those buildings which intersect the suitable_terrain layer.

现在，您应该有一个显示某些建筑的图层作为解决方案，例如：

8.2.2. ★★☆ 自己试试：检查结果

Look at each of the buildings in your new_solution layer. Compare them with the suitable_terrain layer by changing the symbology for the new_solution layer so that it has outlines only. What do you notice about some of the buildings? Are they all suitable just because they intersect with the suitable_terrain layer? Why or why not? Which ones would you deem to be unsuitable?

答案

You may notice that some of the buildings in your new_solution layer have been "sliced" by the Intersection tool. This shows that only part of the building - and therefore only part of the property - lies on suitable terrain. We can therefore sensibly eliminate those buildings from our dataset.

8.2.3. ★★☆ 自己试试：改进分析

从结果可以看出，其中一些建筑并不真正适合，因此我们现在可以细化分析。

We want to ensure that our analysis returns only those buildings which fall entirely within the suitable_terrain layer. How would you achieve this? Use one or more Vector Analysis tools and remember that our buildings are all over 100m squared in size.

答案

目前，您的分析应该是这样的：

视为一个圆形区域，在所有方向上持续100米。

如果它的半径大于100米，那么从它的尺寸 (从各个方向) 减去100米将导致它的一部分留在中间。

Therefore, you can run an interior buffer of 100 meters on your existing suitable_terrain vector layer. In the output of the buffer function, whatever remains of the original layer will represent areas where there is suitable terrain for 100 meters beyond.

例如：

1. 转到 矢量 ► 地理处理工具 ► 缓冲区 打开缓冲区对话框。

2. 设置如下：

   

3. Use the suitable_terrain layer with 10 segments and a buffer distance of -100. (The distance is automatically in meters because your map is using a projected CRS.)

4. 在 exercise_data/residential_development/ 保存输出为 suitable_terrain_continuous100m.shp 。

5. If necessary, move the new layer above your original suitable_terrain layer.

   您的结果将如下所示：

   

6. 现在使用 按位置选择 工具 (矢量 ► 研究工具 ► 按位置选择).

7. 设置如下：

   

8. Select features in new_solution that intersect features in suitable_terrain_continuous100m.shp.

   结果是：

   

   The yellow buildings are selected. Although some of the buildings fall partly outside the new suitable_terrain_continuous100m layer, they lie well within the original suitable_terrain layer and therefore meet all of our requirements.

9. 将选择保存在 exercise_data/residential_development/ 为 final_answer.shp 。

8.2.4. 总结

现在，您已经回答了最初的研究问题，并且可以就开发哪处房产提出建议 (有理由，有分析支持)。

8.2.5. 接下来是？

接下来，您将在第二次作业中展示这些结果。