QGIS Points and Grids

PT: I juiced the pictures up a bit with some cropping. I wonder if you could add image of what these things produce on an actual map? PS: the buttons are a nice touch.

What are Random Points/Regular Points/Vector Grid?

Random points, Regular points, and Vector grid are "Research Tools" which are under the umbrella of fTools (as defined by Carson Farmer (Yr), "tools for vector data analysis and management" Plugin.)

To find fTools:

Step 1: Start QGIS
Step 2: Go to the top of the screen to find "Plugins"
Step 3: Click on "Manage and Install Plugins…"
Step 4: fTools is already installed for you so you can find it in the "Installed" tab of the Plugin Manager.

To find these 3 plugins:

In QGIS, go to the top of the screen to find "Vector" then "Research Tools"


What do Random points, Regular points, and Vector Grid do?

1. random_points.png Random Points —> Generate pseudo-random points over a given input layer. Random Points tool offers two designs: Unstratified Sampling and Stratified Sampling Designs.
A. Unstratified Sampling Design (Entire Layer) with 5 points allows you to randomly generate points in the entire layer.

Step 1: Select your Input Boundary Layer.


Step 2: Select Use this number of points and choose type in number of points you would like to generate (for ex: 5)


Step 3: Once you pick a folder of where you want your output to be located, a pop up message will appear and ask if you would like to create a layer and add that to your existing map canvas. After you clicked Yes, your map should have 5 red points.

B. Stratified Sampling Design (Individual Polygons) with 2 points allows you to generate points in individual polygons or within certain categories based on those individual polygons.

Step 1: Click on the button Use this number of points and type in how many points you would like to generate in each polygon


Step 2: Once you selected the location of the output, a pop up message will ask you if you would like to add that new shapefile/layer to your existing map canvas. You should select Yes. You will see that there are many burgundy points on this map but each polygon only has 2 points.


2. regular_points.png Regular points —> Generate a regular grid of points over a specified region and export them as a point shapefile.

Step 1: Pick your Input Boundary Layer or Input Coordinates


Step 2: Select how many points you would like to generate in the layer. As you can see, the point generated through the use of this tool is located on the bottom right corner like a regular grid of points.


3. vector_grid.png Vector grid —> Generate a line or polygon grid based on user specified grid spacing.

Step 1: Select your Grid Layer


Step 2: You may select the grid extent manually or you can click on the "Update Grid extents from (map) canvas or layer"


Step 3: A pop up message will ask you if you want to add that new layer that you just generated to your existing canvas. You should click Yes to see the result. Your map should look like this. Vector grid created a purple grid layer that covers your entire canvas or layer depending on your selection of grid extents in Step 2.