DIGITIZING IMAGES IN GOOGLE EARTH
G1811 Spring - Discovering Spanish Landscapes
Domingo F. Rasilla
2024-04-28
IMPORTING IMAGES IN GEOTIFF FORMAT.
Google Earth has a good archive of images from the past, but in most cases it does not exceed 30 years. To do this you have to activate them by clicking on the small clock in the toolbar located at the top of the image.
It is possible to import georeferenced images in Google Earth from a foreign source. Next, it will be shown how to import the image corresponding to the “Flight of the year 1956-1957”. These images will be downloaded from the instructor´s website Downloading the image.
Once downloaded to your machine, you will return to Google Earth to import them. To do this, click on the Fichero tab on the toolbar, and search for Importar. From here it is enough to select the file to import, which must have a format readable by Google Earth (*.tiff format).
In the case of GeoTiff files, the program displays a message warning that their size is greater than the maximum size supported by the software. The first option will be chosen: Si quieres crear una superposición a partir de la imagen original, pulsa “Crear superposición.
Once done, the program also requires you to identify in which directory where the partial files will be stored, in *.kml format. It is advisable to create a specific directory to store them, since a large number of files will be created.
Once this is done, the overlay image will appear.
You can control the level of transparency using the tool on the left.
DIGITIZING FEATURES FROM A GEOREFERENCED MAP
It is possible to create custom features and store them in the folder. The mapping tools at the top of the viewer offer custom feature creation such as points (placemark), lines (path) & polygons.
Adding a polygon or a path
Buttons for adding placemarks, paths, and polygons are found in the menu bar.
To add a polygon shape, click the polygon drawing tool. A New Polygon dialogue box appears and the cursor has changed to a polygon drawing tool. It is advisable to drag the previous dialog box away from the area to be digitized, so that it does not get in the way, but it should not be closed.
The digitization process can begin below. To draw the line, a target-shaped cursor appears. Every time the left button is clicked, a dot appears. Successive clicks will join together to form the line. When the scanning is complete, you must return to the dialog box that remains open and press ok. Enter a name and description in the respective fields in the dialogue box. Again, colour and line thickness may be customized as well as the fill colour, and a name and description should be added in the New Polygon dialogue box.
To add a line, click the Add Path tool. Click along the path on the imagery to create a line (as if you are creating the dots for a connect-the-dots puzzle), double-clicking when it is complete. To change the colour, select the Style, Color tab, click the Color box, and select a new colour. Click OK. The width of the line can also be changed at this point by entering a new line thickness.
Adding a placemark
Like paths and polygons, a point (called Placemarks in Google Earth) can be added and the symbol style, size, and colour customized. To create a new placemark, click on the drawing pin icon. A drawing pin with a yellow flashing box around it will appear on the map. You can drag this to your exact location using thee cursor and mouse. (Note: zoom in for greater accuracy). A dialogue box will also appear. Type a name for your placemark. You can also write a description in this area, which will be displayed when you click on the icon. Once you have chosen the location, names and description, click ‘OK’.
It is possible to add content to the placemarks. When you are creating the Placemark, a box will show up with many choices to add information: Name, description, colors, etc. etc.
There are also two buttons, one for “Add Image” and one for “Add Link.” When you click on the “Add Image” button you get a field that says, “Image URL,”where you place a URL which points to the location of the image that is already online. Important: images can only be added if they are placed somewhere online, such as Flickr, or even your own WordPress site (such as a UO Blogs site that you’ve created).
When you click on the “Add Link” button you’ll see a field that says, “Link URL” where you put the hyperlink to the content that is online. This content can be an article in Wikipedia, a related journal article or even a .pdf file that is being hosted online.
When satisfied with your changes, click OK to return to the map viewer. **You can always adjust the properties by right-clicking the feature in the table of contents and selecting Properties from the menu.
SAVING FEATURES
The new feature will be stored by default in the “Temporary Sites” folder in KML or KMZ (zipped KML) format (native to Google). This means that when you exit Google Earth, the layer will disappear. To save it, you must right-click and press “Save to my places” or any other directory of the student’s choice. When you open Google Earth next time, this layer will automatically appear if it is located in “My Places.” If this is not the case and it has been saved as a *.kml file in another directory on the hard drive, you will have to press Open and select the corresponding kml file.
To view a KMZ or KML file, run Google Earth and select File > Open. Navigate to the file of interest and open it. The layers will appear under Places > Temporary Places.