Creating and modifying shapefiles

Shape files (.shp) are QGIS's way of storing location, shape, and attributes of geographic features (aka labels). Continuing our example, we'll take a look at how to create shape files in QGIS.

1. Open QGIS.

2. Open the GeoTiff file(s) to be labeled.

3. Open the Bing Satellite.

   

   Example of step 3
4. Make sure the Data Source Manager Toolbar is on your screen.

5. In the Data Source Manager Toolbar at the top, select the icon with four dots that says New Shapefile Layer... when hovered over.

   

   New Shapefile Layer

   

   New Shapefile Layer menu
6. In the window that appears begin by giving the file a name next to File name.

Try to give it a unique name that won't be confusing later.

• For example, you could include the name of the instrument, the date that the data corresponds to, and the feature being labeled (e.g. eMAS_08022019_fire). However, this is just a guideline so feel free to be as detailed as you'd like.

• Naming the shapefile after the original file with the specific feature at the end is also always a safe bet (e.g. eMASL1B_19910_06_20190806_1815_1824_V03_fire).

1. Then, select the button with 3 dots to the right of the file name, choose a directory for the shapefile to be stored in, and click save.

Stay consistent with how/where shape files are stored, we'll need to access their file paths later.

1. For Geometry type, select Polygon.

This allows us to have a 2D shape rather than just a line.

1. At the bottom right of the window click OK.

Note: if you'd like to change the color of the shapefile, select the shapefile from the Layers panel and hover over to the Layer Styling panel and select any color.

Congrats, you now have your first shape file! Labeling is pretty simple.

1. With the data layer selected (in the Layers panel), navigate to the Layer Styling panel and choose which spectral band is best for viewing the feature you are labeling. For more documentation on this, see Understanding the data.

2. Now, with the shapefile layer selected, select the yellow pencil button from the Digitizing toolbar that says Toggle Editing when hovered over.

3. Then select the green button to the right of the pencil (that appears when the pencil is selected) that says Add Polygon Feature when hovered over.

Toolbars

1. Click on the perimeter of the feature you would like to label and begin labeling.

2. Once you have completed your label, right click on the screen and select OK in the pop up that appears.

Congrats, you now have your first label! Use these steps to create as many labels as needed.

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Here is an example of a label of the burnscar from the William's Flat's Fire.

Figure 1. eMAS William's Flat's Fire, greyband 9, burnscar label

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Note: It is important to create a background label(s) so that SIT-FUSE can properly segment key features of the image.

There are a few ways to go about creating a background label.

1

For each image you can create a general label (e.g. <file_name>_background.shp) that encompasses everything except the features you are labeling.

For example, if you have 2 features you're labeling: smoke and fire, then the background label would cover everything except those two.

2

Or for each image you can create a background label for each specific feature (e.g. <file_name>_fire_background.shp, <file_name>_smoke_background.shp).

This label encompasses everything except that specific feature. For example, if you have 2 features you're labeling, smoke and fire, it would be okay if the background label for the fire overlapped onto the regular label for the smoke in this case, and vice versa. As long as the fire background label does not overlap onto the actual fire label.

The advantage of the second case is that it may generate more accurate output, as SIT-FUSE would clearly know where each feature begins and ends based on the surrounding background label.

Additionally, SIT-FUSE has a built in functionality that can generate these background labels based on the labels of the actual features.