Practical Manual - Malareo

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Once you are happy with your line layer you can toggle editing off and save the layer. Be creative with your road names. Polygons Digitising polygons is essentially the same as digitising lines. The difference is that a polygons must have congruent side and must not overlap. To ensure common boundaries enable the topological snapping option for the layer you are digitising. Within GIS dependant on the scale you are working at it could be preferable to digitise a point versus a polygon. For example: Tress can be represented as polygons or as points. If you want to show the location of a tree or it is preferable to use a point however if you are working with tree canopy’s and want to deternine area of all tree canopies then polygons would be preferable. The decision as to how to digitise is dependant on your need. Challenge: Create an polygon layer called HC_Buildings and digitise the outer extents of each building that you represented as a point in your buildings layer. Remember to name them. GPS data GPS units such as the Garmin or Magallan handheld units allow you to store waypoints and tracks as you move around. A prime example would be mapping the location of a homestead where a case of malaria was found. There are various formats that are used to transfer GPS data from the GPS units to GIS one of these is the GPX format GPS Standard Exchange Format. This can be used by most GPS units and GIS systems to transfer data. There are numerous freeware programs to download files should you want to create basic text files instead of importing them directly into a GIS. The include G7toWin and DNRGarmin. In this exercise you will import a GPX file into a new project and add a Spot image as a back drop. Create a blank project. Select the GPS Tools. This opens the GPS Tools window. Select the Load GPX file tab (top left tab)Browse to find the GPS_pnts.gpx file from your prac3 directory and select it. Make sure waypoint types are checked and click ok. QGIS for Malaria Page 28
If you are interested in seeing the format you can view the GPX file in notepad or a text viewer. As you can see this file was created by DNR Garmin as this file was downloaded using DNR Garmin software. The text format is however vastly different to a standard csv file. When working with GPS data it is often worth saving the GPS data into both a gpx and a csv file to ensure no loss of data. Next you will load the backdrop image. Add a raster layer called Umfolozi. This is a spot image clipped to the extent of the main study area. In this case the points are locations soil samples within Hlhulwe-Umfolozi Game reserve. It is always safer to save a GPS event theme (waypoint layer as a new shapefile and you can do so by right clicking on the layer and selecting Save as. This practical has introduced you to the concepts of acquiring data, opening data, importing data nad creating your own data through digitizing. The QGIS manual contains further details on Data capture and digitizing. The manual is included as a PDF in your course notes. QGIS for Malaria Page 29
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 and 14: It is important to note that althou
Page 15 and 16: Open your Identify features and exa
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: Continue digitising the other roads
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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