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Looking at the chi map in QGIS

One we run the analysis, we can have a look at the results in QGIS. The steps will be similar in ArcMap, but we show QGIS here since it is open source.

  1. In QGIS the add data button looks like this:

    Add data
    Figure 1. Open raster data in QGIS

  2. Find the data rasters and add them:

    1. WA_DArea.bil

    2. WA_SO.bil

  3. To change the styling of these, see the section [Looking at the first analysis in QGIS].

  4. Here is a coloured version of the stream order raster:

    stream order
    Figure 2. Stream orders over the elevation raster of the Killmade Burn, Scotland

Adding csv data

  1. It is a bit more difficult to add csv data (csv stands for comma separated values). In QGIS, you need to click on the layer menu and then scroll to the add text delimeted layer button:

    Add csv
    Figure 3. Add csv data

  2. We will add the WA_MChiSegmented.csv layer. Once you select that file (using browse) you will see something like this:

    Create layer
    Figure 4. Create layer menu

  3. Hit okay. You will then be asked what coordinate system you want. All csv data from LSDTopoTools is in the WGS84 coordinate system! Your rasters are typically in a local coordinate system but we convert point data to WGS84 so that they can be loaded onto web mapping platforms (i.e., Google Earth). The upshot is that you need to use WGS84 for the coordinate system.

  4. All coordinate systems have a code, called an EPSG code, and the EPSG code for WGS84 is 4326: search for this (in the Filter form) and select it:

    EPSG:4325
    Figure 5. Choose WGS 84 coordinate system with EPSG:4325

  5. You should get something that looks like this:

    Chi point data
    Figure 6. Point data
    Warning
    		 Sometimes you need to click in the little symbol that looks like a globe in the bottom right corner of QGIS an enable on the fly CRS transformation.

  6. Okay, this doesn’t look so great, right click on properties of the layer, choose graduated symbols, select the m_chi column (this is chi slope) pick a nice colour ramp, and then click on classify:

    Chi map
    Figure 7. Chi map coloured by chi steepness