Practical Manual - Malareo

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Open the attribute table. Notice there are no Longitude latitude columns but there is a shape length column. Notice the figures, (Very small numbers) these distances are in degrees, which are not constant dependant on where you are on the globe. To get an idea of distance you will now measure a length of Conductor. Go to the bookmark Measure. Select the measure line tool from the toolbar. Starting at the top left of the line using the left mouse button click along the line following the line to its end. Notice in the pop up window the distance is shown in metres and the distances increase with each added click. What is the approximate total length of the line Next you will look at the relative accuracy of layers. Open the bookmak Scale. This is an area on the Orange river on the border between South Africa and South West Africa Notice that while at full zoom differences between the layers are not visible, but when zoomed in you can see the lines although similar do not coincide. When undertaking analysis or editing data, this can cause problems. Be aware of the data you are using. Notice how the river has 2 lines (one on either side of the border representing the width of the river.) Also notice that the SA Provinces do not match the Boundaries for South Africa. (This is because they are from different sources and digitized (created) at different levels or scales. You can use the Zoom Last tool to zoom to the last view extent or zoom full to zoom to the full extents of all layers. Be aware of these issues when acquiring or using different data sets. Raster Data. Open the project called raster. This project contains a Digital elevation model, where each pixel represents the average altitude across that area of land in the country. The pixel size is 800m x 800m. Notice there are vector layers present in the Map legend. Turn these on. Do the rivers match the Elevation Zoom into a river. Notice the size of the pixels get larger as you zoom in while the vector lines stay the same thickness. This is one of the advantages of vector GIS over raster GIS. Symbols used to represent lines and points will stay the same point size irrelevant of scale or zoom. However pixels have a set size and will increase or decrease in relative size as you zoom in or out. Use the Zoom bookmarks to show this or zoom in interactively. QGIS for Malaria Page 14
Open your Identify features and examine the values of pixels for both Raster layers. Notice that although there are 2 Raster layers displaying elevation, only the Africa_Elev contains the actual height values. The colour image contains red green and blue values and cannot be used to determine altitude, but can be used to drape over an elevation layer to increase visibility or contrast. Use your transparency to make the Africa layer 70% transparent. Zoom to the full extent of your map and examine your map. Again it is important to know your data and determine what each layer represents. Challenges The following exercises are optional but allow you to interact more intensly with the software. Undertake the following: Create a map of Africa integrating the Africa Elevation data with the malaria_2008 cases data and Rivers. Save the output as a JPG image Using Any Project Zoom into South Africa at a scale of 10 000 000. (Use your scale window) and add the Rivers_SA layer. How Many Countries are there in the Malaria_Cases_2008 layer What is the Mean number of Cases for Angola, Zambia and Mozambique Combined Using the basic statistics tool, determine the Mean number of cases of Malaria across Africa QGIS for Malaria Page 15
Page 1 and 2: Introduction to Geographic Informat
Page 3 and 4: occurrences you can gain a better u
Page 5 and 6: Once in the folder, using your mous
Page 7 and 8: Map Legend You now have 2 layers lo
Page 9 and 10: Select the Identify features tool a
Page 11 and 12: 30% release it and click on Apply a
Page 13: It is important to note that althou
Page 17 and 18: Acquiring Spatial Data There are nu
Page 19 and 20: This adds the shapefile to the lege
Page 21 and 22: You will be creating a layer using
Page 23 and 24: This opens a co-ordinate reference
Page 25 and 26: Next you will create a line layer (
Page 27 and 28: Continue digitising the other roads
Page 29 and 30: If you are interested in seeing the
Page 31 and 32: PROJECT COORDINATE REFERENCE SYSTEM
Page 33 and 34: Task 1: Changing the Default CRS in
Page 35 and 36: Practical 5 Tabular Data Queries Ou
Page 37 and 38: ecords. Switching and clearing yo
Page 39 and 40: Practical 6 Spatial Analysis Outlin
Page 41 and 42: Task 1: Open a new QGIS project. A
Page 43 and 44: In order to make measurements in un
Page 45 and 46: Now to measure along the length of
Page 47 and 48: Buffer and Dissolve Buffer: Often i
Page 49 and 50: Open the Attribute Table for the Pr
Page 51 and 52: The result window shows the number
Page 53 and 54: Task 5: Slope Analysis Open a new
Page 55 and 56: Active Layers in the TOC Mathematic
Page 57 and 58: In this practical you will undertak
Page 59 and 60: 1999 (which was year 1 of the 10 ye
Page 61 and 62: updated with percentages of prevale
Page 63 and 64: Click on Set to current extent Leav
Page 65 and 66:
Practical 8 Summary Practical Outli
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Practical Manual - Malareo

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