这是ArcLessons上的一个很新的GIS课例，原文地址见：

http://edcommunity.esri.com/arclessons/lesson.cfm?id=616

 

这个课例本来是为大学生准备的，但也适用于中学生，我看了过程，觉得其中涉及到的电脑操作对我们的学生来说应该是很简单的，而其中需要用到的GIS软件操作也不难，学生在明师的指导下应该很快能掌握。

 

课程大致这样设计：给出足够的图层数据---文中对数据来源轻描淡写，而我认为这恰恰是我们准备GIS辅助教学的最难的地方，给出茶叶的种植条件，要求在肯尼亚地图上找出能够种植茶叶的区域。

其实就是一个GIS的模式分析问题。

 

他的课程设计在我们看来很简单，有两大特点：一是操作步骤很详细，指导性很强；二是整个课程基本由问题构成，没有知识和原理的讲授和灌输。

 

我觉得凡是GIS课例都必须首先考虑清楚这个问题：这个课是不是一定要使用GIS技术？这个课不使用GIS是否也能大到同样的效果。但是至少这个课例向我们展示了非要使用GIS于地理课堂的必要性。

 

另外，关于茶叶的生长条件，文中给出的六个标准不知道是不是足够权威？还是作者根据本课例的需要自己创作的？

 

我以前给学生讲茶叶，必讲印度和斯里兰卡，却不知道肯尼亚也是种茶叶的大户，也算是另一种收获。

 

ArcLessons是public license还是CC license? 无论那种都不妨碍我把原文附录于此吧。不过图去掉了，想看全文的请浏览上面那个网址。

Selecting Sites for Tea Cultivation in Kenya with GIS

Your Name:_______________

Goal:  To use GIS and the spatial framework to select suitable sites for growing tea in Kenya, and by extension, to understand the physical and cultural geography of Kenya, and how to analyze spatial data.

Software:  ArcGIS 10 and above, from Esri. 

Audience:  Students working through this lesson should be familiar with computer file management, and some familiarity with ArcGIS will be helpful.

Academic Level:  This lesson is aimed at the university level, although more advanced students at the secondary level will be able to use it.

Time Required:  This lesson contains 30 questions and requires 2 to 4 hours to complete.

Geospatial Skills
1)  Tabular data joining, sort, query, and analysis.
2)  Spatial data sort, query, and analysis.
3)  Overlay and other geoprocessing operations.
4)  Symbolizing and classifying data.
5)  Making a decision in a GIS environment.

Issue
Tea is an important world cash crop, including for Kenya.  The Kenya Tea Development Company is a cooperative of growers that represents 28% of Kenya’s total export earnings. It is the largest tea cooperative in the country.  Over 400,000 growers are in its network, cultivating land that is over 86,000 hectares and produces over 700 million kg of tea annually.  

Hearing about your GIS skills, the Kenya Tea Development Company has hired you to select additional lands that might be suitable for tea cultivation. These lands need to have the following characteristics:

1.  It must be grown on moderately high ground, between 914 meters and 2,133 meters above sea level. 

2.  It cannot be on any water-related land cover, including inundated areas, wetlands, or distorted water surface.

3.  It cannot be in an urban area.

4.  It cannot be within 500 meters of a populated place.

5.  It cannot be within 2000 meters of a mine.

6.  It must be within 5 km of a road, to reduce transport costs.

Data Management
Create a folder on your computer or on the network where you will store the data.  Make sure this folder has a logical name so that you will understand what its contents are.

The data for this lesson was created by the World Resources Institute (WRI).

Access ArcMap.

 

Open the wri_kenya.mxd map document.

 

1)  Become familiar with each of the data layers in your map document, filling out the following data table:

 

Next, set your workspaces in this project so you will be storing the data in the correct and logical location. 

 

Go to the Geoprocessing pull-down menu and then to Geoprocessingà Environments à Workspace.  

 

Set the current workspace and the scratch workspace to the geodatabase, as shown below, that you are using for this course.

 

Let’s turn our attention first to criteria 4 and 5.  In order to determine which land is far away from populated places and mines, we must first determine which land is near these features, and then switch the selection.  Expand the Catalog tab on the right (you may need to use Windowsà Catalog to pull up the catalog), move to Toolboxes à System Toolboxes à Analysis Tools à Proximity à Buffer (or simply search for “Buffer” and pull up the tool), as follows, naming your output populated_places_500m_buffer:

 

Examine your new layer.

 

2)  Is your new layer a point, line, or polygon feature class?   Why?

 

3)  What is the shape of your buffers?  Why?

 

4)  Are your buffers 500 meters from the populated place to the edge of the buffer or are they 500 meters in diameter?

 

Repeat the process to create 2000 meter buffers around mines.

 

5)  What is the spatial pattern of mines in Kenya?

 

Let’s deal with criterion #6 next.  Examine the roads layer. 

 

6)  Does the roads layer include other things besides roads?

 

For this study, you will only include primary and secondary roads.  Use Selection à Select by attribute on primary and secondary roads, as follows:

 

Now, create 5 km buffers around primary and secondary roads. 

 

7)  What is the shape of your roads buffers?   Why?

 

You want your buffer layer to include only the primary and secondary roads, not all of the features in the roads layer.

 

Check the roads buffer. 

 

8)  Does it only include the primary and secondary roads?

 

9)  Open your attribute table for your roads buffers.  How many polygons do you have?

 

Run, under Data Management tools à Generalization à Dissolve on your roads buffers, as follows:

 

 

Toggle on and off your original roads buffer with your dissolved roads buffer. 

 

10)  What did the dissolve tool accomplish?

 

11)  How many records are in your dissolved buffer table?

 

Now that you have created areas that will meet criteria #4, #5, and #6, you  can turn your attention to the final analysis, beginning with criterion #1 about elevation.

 

Use Selection from the top pull-down menus, and à Select By Attribute, for the elevation layer, which is named “hypso_net_poly”, as follows:

 

 

To see the list of values possible, be sure to click on “Get Unique Values” before finishing your selection.

 

When done, examine your map.  You may wish to, under Selectionà Selection Options, change the selection color from the default of cyan to yellow or something easy to notice.

 

12)  What is the pattern of that specific elevation range in Kenya?

Examine your attribute table. 

 

13)  How many polygons of land are under consideration for tea cultivation that meet the elevation requirement?

 

Right click on the layer à Selection à Create layer from selected features.  This will create a layer file just for the areas meeting the elevation requirement.   Note that it is just a layer file, rather than a new dataset.  This layer file still points to the original data file named hypso_net_poly. 

 

14)  How many records are in your hypso_net_poly_selection layer?  Why?

 

In ArcToolbox, find the Analysisà Overlay à Erase tool, and erase the water areas (landcover_water_poly) from your hyso_net_poly_selection (where the elevation is suitable), naming your output feature class elev_ok_water_ok.

 

 

15) Toggle the layer elev_ok_water_ok on and off with your suitable elevation layer and your landcover_water_poly layer.  Explain what the differences are and what the erase tool did.

 

16)  How many polygons are now suitable for tea cultivation?

 

Next, erase urban areas from your elev_ok_water_ok layer, and name the output elev_water_urban_ok.

 

17) How many polygons are now suitable for tea cultivation?

 

Even thought the number of polygons is the same as before the urban areas were erased, the total area is reduced. 

 

Right click on the shape_area field in both attribute tables and Summarize.  The data in shape_area is in square meters.  Fill in the following data:

 

 

 rase your populated place buffers from the elev_water_urban_ok layer, creating the output elev_water_urban_popplace_ok. 

 

Examine your map. 

 

19)  Do you have “holes” now in your area under consideration that represent areas near populated places?

 

Next, erase your areas near mines from the areas under consideration.

 

Check your map. 

 

20)  Are the areas near mines now excluded from the land under consideration?

 

You have now considered nearly all of the criteria except for roads.  Recall earlier that you created a buffer layer representing all land within 5 km of primary and secondary roads.  Run a Data Managementà Analysis Tools à Overlay à Intersect.  When the tool appears, select “Show Help” and read the tool help for Intersect.

 

21)  Explain in your own words what this tool does.

 

You will intersect your roads buffers with the layer (elev_water_urban_popplace_mines) that considered the other 5 layers.  Use these two inputs with an appropriately named output of “final_sites”, as follows:

 

 

22)  How many polygons are in your final consideration layer?

 

You were just about to create a report and final map when you receive a call from the tea cooperative indicating that they want one more factor to be considered. Tea plants can only be planted every 1.5 meters to avoid overcrowding and for maximum sunlight and production of tea leaves. 

 

23)  If 50000 plants is considered a minimum below which it is not economically feasible to grow tea, and if tea can only be planted at a density of 1 plant every 1.5 square meters, what is the minimum total area that should be considered?  Show your work:

 

 

 

Use Select By Location to select the pieces of land that meet the other criteria but are too small.

 

24)  How many pieces of land are too small?

 

Switch selection to obtain all of the acceptable pieces of land, as follows:

 

25)  How many sites are in your final consideration?

 

26)  Select what you believe would be 3 good pieces of land to grow tea on in the final sites layer.  Describe how far these 3 pieces of land are located from Nairobi, and where they are located in Kenya.

 

Create a final map showing your data for your report for the Kenya Tea Development Company.  All of the information you wish to include in the final plot will be in a "layout view."  Access the layout view by selecting the button on the lower left of the data frame.  Alternatively, you could also use the View pulldown menu, and select Layout View.

 

You may also wish to use Customize à Toolbarsà Layout to display the layout tools. 

 

Using the Insert pull down menu, add:

A scale bar in kilometers,

A title,

Your name,

The date.

A text box explaining how you determined the tea cultivation sites.
      An photograph of tea cultivation.

Any other information you think is pertinent.

 

27)   Copy your layout and paste in the document below, or print and attach.

 

Save your map document.

 

28)  What other layers might you have wanted to deepen your analysis of selecting suitable tea cultivation sites?

 

29)  Summarize in a few sentences what you have learned about the spatial pattern of suitable tea cultivation sites in this lesson.

 

30)  How did GIS help you in your analysis of tea cultivation and about Kenya’s cultural and physical geography?