Opening and viewing a GIS (Geographic Information System) file.
For your projects you are going to use GIS software created by the company ESRI. It is called ArcGIS 10, and is high-end analytical GIS software. You will see that it contains an amazing amount of functions and tools so follow the instructions on using it closely so that you don’t get lost.
GIS maps are usually made up of several layers of geographic information which lie over each other. These layers or coverages may be of three types. At the top are the layers of points such as towns, under these are placed the layers of lines such as roads and rivers. The bottom layers are the shapes or polygons e.g. municipal or country boundaries. We are going to use a polygon coverage today i.e. the boundaries of the countries of the world. You will be using this layer for your projects.
A standard way of storing GIS information which was created by ESRI is the shape file. This is a misnomer as a shape file is in fact about five different files which work together to show the coverage in the GIS. The three main files (there are other besides there) which make up a shape file and that you should take note of are:
1. xxx.shp - this file contains the primary geographic reference data for the coverage e.g. the data which is needed for the GIS software to draw the outline of the countries on the map
2. xxx.dbf – this file contains a table of information related to each one of the polygons which in the case represent countries
3. xxx.shx – this file improves the functionality of the coverage.
We are going to launch ArcGIS 10 , add the world map coverage (the shape file) as a layer and learn how to use the navigation and identify tools in this software - the most fundamental tools in any GIS.
Introduction to using ArcGIS 10
A. Launching the ArcMap 10
You can launch ArcMap 10 by
1. Clicking on the ArcMap 10 icon on the decktop (if it is available) or finding it on the start menu
2. Going to Start –All progtams – AccGIS – ArcMap 10.
B. Adding a new blank map
When the software launches a window will popup which gives you the options for opening an existing .mxd (map file) or start a new mxd file.(Note a map file or .mxd file must not be confused with the coverage or shape file described earlier). The .mxd file contains all the information about the map you have made by adding different converages as layers and adjusting how they coloured on the map. These changes do not alter the geographic information of the shape file but merely change how you have decided to display the information in on your particular map (.mxd) file.
1. In the pop up box choose New map in the left hand menu.
2. A series of large icons will appear on the right, click on Blank map.
3. A map containing no added layers will appear
C. Adding the world map coverage as a layer to your map.
1. Click on the Add data icon which should appear near the left of the first toolbar. Note you may have to look for the icon as the menu bar on your computers ArcGIS 10 installation may have been shifted or even removed by a previous user.
2. Navigate to where you saved the downloaded World map shape file and click on it. The world map will appear as a layer in the list of layer in the contents window to the left of the map. The map of the world will appear in the main map window.
D. Zooming into and out of the map.
There are two ways you can now move around on the map
- Rolling your mouse wheel forward you will zoom into the map and backwards you will zoom out. Left click and drag the mouse to shift the map frame with our zooming in or out.
- The first eight tool on the second toolbar are navigation tools
They are zoom in, Zoom out, pan(shit the map), zoom to full extent, fixed zoom in , fixed zoom out, back to previous extents (where you were before movement on the map), forward thorugh the pl.ace you have been.
Try using these tools on your map
E. Identifying features
Now you will want to know what the countries are on the map. You need to extract information out of the world map layer. This information comes out of the attribute table (remember its information is saved in the . dbf file of a shape file.)
1. Click on the identify feature icon which is in the second toolbar.
2. Click on a country on the map and a box will appear containing its features
F. Open the attribute table
You can open the attribute table which contains data about all the polygons or shape which make up the map. In this case these represent the countries of the world. The information you just accessed using the identify features tool comes from this table
1. Right click on the world map layer in the left hand table of contents window.
2. Choose Open attribute table from the popup menu. A window will appear containing a spread sheet with the attribute data from the world map coverage.
G. Saving the map
1. Use the normal windows save icon to save you work as a .mxd file. It is best to save this file in the same directory as where you saved the shape file.
2. AS in other windows programs you can also Click on file and then save.