FFS – Land degradation assessment
Training module
Lesson 1
Thomas Gumbricht
ICRAF
FFS – Land degradation assessment Training module Lesson 1 Thomas Gumbricht ICRAF |
Using Farmer Field Schools Approaches to Overcome Land Degradation in Agro-Pastoral Areas of Kenya
Land degradation assessment – Baseline survey on spatial analysis of land cover / degradation trends and Toolkit Development.
Training module created by Thomas Gumbricht, www.mapjourney.com
Last updated: October 2007
LESSON 1 – DIVA-GIS BASICS
Lesson overview
In this lesson you will learn about GIS data layers, and how to add and remove them from a DIVA-GIS project, how to turn layers on and off, and change the display order. You will also learn how to retrieve information about geographic features, and see the difference between vector and image data.
With the project opened, save it as a new project (e.g. with the name lesson1) via the menu: Project – Save As. See lesson 0 to repeat saving a project if you need.
When you click Add Layer a standard windows Open folder and file navigation window will pop up. Navigate the folder \data_spatial\ke\mapdata\politic.
As you can see in the lower section of the Open window DIVA-GIS can work with several types of files, including: shape files (shp – files with vector GIS data), grid files (grd, files with raster GIS data), and various standard image formats (tif, jpg, sid, arc). Do not worry about this now, it will be explained later. The most common format for GIS data is as vectors, and DIVA-GIS uses shape (*.shp) files for working with vectors.
Click the drop down menu for Files of type:, and select Shapefiles (*.shp) as shown below.
Add the vector layer ke_country-index.shp (dependent on your computer setting you can also click or double click on the filename to add it).
DIVA-GIS displays the content of the shape file in the Data View, and the legend in the Legend, to the left. Note also how most of the tools became colored when you added the map layer – DIVA-GIS now has some data to operate on.
The project CD contains around almost a hundred shape files for you to start working with. With each shape file follows a jpg-image file (*.jpg). The jpg file can be viewed with most image programs (paint, photoshop etc), or using a web-browser (Internet Explorer, FireFox, Netscape, Opera, Safari etc). The jpg-images that are included can all be viewed via the project data catalogue web-page. But they are also possible to view in DIVA-GIS (or any other GIS). The jpg-images are almost all symbolized (that is, have colors and patterns) that are standard. And you can use the jpg-images in your projects, just as background images, or as templates for symbolizing your own GIS data layers. If you have a license for ArcView or ArcGIS there is a ready-made project file that contains most of data layers available on the CD (except the time-series data, there are simply too many layers to include). The ArcView project file is in the directory \av on the project CD. You might have to install some of the included extensions (also under the \av folder on the project CD) if you want to see all the data in ArcView.
In the Legend View you select which layers to be shown in the Data View, and also which layer(s) the Tools should operate on. To turn on and turn off a layer, click the checkbox to the left of the layer name. In the example below the checkbox for ke_dnoint is unchecked, and the drainage points are not shown in the Data View.
To check/uncheck all layers in the Legend hold down the ctrl-key and click any layer that is on.
When you clicked in the checkbox the layer you clicked also got a highlighted frame around it (ke_dnoint in the example above). The lifted frame of ke_dnpoint indicates that ke_dnpoint is now the active layer. Any layer-related operation that you will now do will work on the highlighted layer(s) only. You do not need to check or uncheck the checkbox to highlight a layer – just click anywhere else on the layer in the Legend (e.g. on the small symbol or the text) and that layer will be selected as the active layer. To select more than one layer to be active, hold down both the ctrl and shift keys, then use the mouse to click on the layers you want to make active in the Legend. All active layers will appear lifted in the Legend View. You can also deselect layers in this way.
Click on the layer ke_country-index in the Legend to make it active (it appears lifted), make sure the Identify Feature tool is active, and click inside the map (Kenya in the example below).
A pop up window (called Identify) will show you information about the feature you clicked. A feature or record is a single point, line or polygon (as in the case above) that represent one particular phenomena in the map layer – in this case a country in the map layer ke_country-index.
You can also get the zoom and pan functions from the menu, under the Map option.
Under the map menu you also find the Properties option. Select the Properties option to see the Map Properties of your project.
So far you have only worked with vector map layers. But DIVA-GIS can also work with images (jpg, tif, sid and arc) and grid files (introduced in lesson 4). Use the Add Layer tool to add both a vector file and an image file showing land degradation, navigate to \data_spatial\ke\mapdata\landstatus and add both the jpg and shp file for the layer ke_glasod_geo – you can select both at the same time by holding down the ctrl key.
In the Data View the added layers end up at the top in the Legend. As the jpg layer is an image it covers all the layers below in the Legend, hence you only can see the image and the layers positioned above it in the Legend.
You can easily change the hierarchical display order in DIVA-GIS. Use the mouse to grab the image layer for ke_glasod_geo (image), make it active and click and hold the left mouse button, then drag the legend of the layer to the bottom of the Legend. A black frame will indicate the movement and position of the legend.
You can also change a layers legend position, and do other things, by making a layer active and then click the right mouse button pointing at the layer in the Legend. By doing that a small popup window will appear as shown below.
One of the options in the popup menu above is to include an overview map. To make an overview map you can also just click F7, or go via the menu: Map – Overview Map. You can toggle between including and excluding the map by clicking F7 (or one of the other options) again. Choose the layer you want to use for making an overview map, and make it active. Then right click on the legend, and click Add to Overview Map, in the popup window (the one shown above). In the example below, the ke_country-index layer was used to create the overview map. By right clicking in the overview map, you get different options for designing the overview map, including adding layers not used in the Data View.
In the Identify window information about land degradation for the feature you clicked will be shown. The land degradation map in ke_glasod_geo is from the Global Assessment of Human-Induced Land Degradation (GLASOD), a United Nations Environment Program (UNEP) funded project that complied land degradation data in cooperation with a large number of soil scientists throughout the world. The legend for GLASOD as symbolized (colored) in ke_glasod_geo.jpg is shown below, to see the full documentation click here. All the documents and backgrounds on the data layers, as well as jpg image files, and most legends can be reached via the project data catalog web-page.
You will work more with GLASOD in other lessons. Before ending this lesson, save your project.