- 1.Please start QGIS and add the following layers (from bottom to top)
a.Orthophoto (2_109898.tif)
b.Nwi44p1.shp and Nwi38p1.shp (NWI dataset)
c.Wetdep_connp1.shp
- 2.Change Symbology
As you see NWI layers are continuous, so you cannot see through them. Field “poly_code” consists of codes for different features. Features with code 0 and 1 are upland and open water, which are no interest for us. Let’s change symbology of NWI layers, so we depict only features we have interest in.
a.Select one of NWI layers, right-click and click on “ Properties”.
b.Click on “Symbology” tab
c.Select “Unique value” in Legend Type
d.Select “Poly_code” in Classification Field
e.Then click on “0” and change “Fill Pattern” to transparent one. Do the same for code 1. Click 0K. (Figure 1)
Nwi – datalayer (values of poly_code field):
0 = Upland (non-wetland areas) 1 = Predominantly Open Water 2 = Estuarine, sub-tidal Marine Systems 3 = Estuarine, intertidal 4 = Non-tidal, aquatic bed 5 = Non-tidal, emergent vegetation 6 = Forested wetlands 7 = Non-tidal, scrub-shrub 8 = Non-tidal, unconsolidated shore 9 = Non-tidal, farmed land, bogs 10 = Tidal, channels
Your TOC should look similar to this one:
Repeat the same for the second NWI layer.
Zoom to the Orthophoto extent.
Make the “Wetdep_connp1” layer transparent, and change the outline color to bright yellow and the outline width to 2. Now you should be able to see the differences in the data sets (NWI and DEP).
Zoom in/pan and identify some problematic areas. What we would like to do now is to outline areas we need to explore. Let’s create a new vector layer “StudyAreas.shp”.
- 3.Click “Layer” > “New Vector Layer” in the main menu.
a.Select “Polygon” as layer type and add attributes. Click OK.
b.Then specify a name for new layer to save as. (“ StudyArea.shp). The new layer will be added to the TOC. The layer is empty.
c.Now we can add new features to the layer. First we need to switch this layer into “editing mode”. Select layer, right click and select “Start Editing” or "Allow Editing" depending on the version you are working with.
d.Layer is now in editable mode
e.Click on the “capture polygons” tool.
or 
f.Start digitizing features. Left-click to add vertex, right-click to complete the polygon. (Note you cannot delete vertices/polygons).
g.Add attribute information to the feature
h.Continue adding study areas.
i.When done, be sure that you “closed” editing mode. Selecting “ stop editing in the context menu” and save your changes.
You now have a vector layer (StudyAreas.shp) with the outlines of areas you need to explore.
Now let’s add a point layer and identify some locations to take measurements. Again, you will use the orthophoto as the main source of information for your preliminary decisions. Later you can use this layer to delegate some research work to your assistants/colleagues.
- 4.Click “layer > New Vector Layer”.
a.Specify point as the type of layer and create the attributes pid as an integer and name as a string.
b.Save the layer as MeasurePoints.shp.
c.Switch to editing mode
d.Start capturing points and filling in the attribute data
e.Stop editing.
f.Save your work.