Saturday, August 26, 2017

Adding Free Satellite Imagery Layer in QGIS

Free satellite imagery
Free satellite imagery with high resolution can be viewed with Google Earth. Google Earth is a popular tool to view satellite imagery at global scope. But Google earth is just a visualization tool to visualize geodata with its KML/KMZ data file. Frequently, we need more sophisticated way how to visualize satellite imagery data and overlay it with other data format in a GIS Desktop software like ArcGIS or QGIS. In this post we will see how to add free satellite imagery layer in an open source GIS software QGIS. There are two ways that we can add free satellite imagery layer in QGIS. First, using Openlayers Plugin and secondly using ESRI World Imagery.

Free Satellite Imagery with Openlayers Plugin

Using Openlayers Plugin, we can add free satellite imagery layer from Google or Bing. But before using this plugin, we have to make sure the plugin is already installed into QGIS software. To check if it  already installed or not, can be done in the following way.
1. In the menu Plugins, select Manage and Install Plugins...(See figure 1).

Manage and Install Plugin menu
Figure 1. Manage and Install Plugin menu
 2. Plugins window appears as in figure 2. In the left panel select Installed. If Openlayers plugin already installed, it will appear in the right panel. If not, select All and type Openlayers in Search toolbar (see figure 2). The Openlayers plugin will show up. Select it and click Install plugin button in the right bottom window. When installation finish, close the window.

QGIS plugin window
Figure 2. QGIS plugin window
3. The installed Openlayers plugin can be found in the Web menu. To add google satellite imagery, select Web >> Openlayers plugin >> Google Maps >> Google Satellite. (See figure 3)
Adding Google Satellit Imagery with Openlayers plugin
Figure 3. Adding Google Satellit Imagery with Openlayers plugin
4. The satellite imagery layer will be added to QGIS map window as in figure 4. Zoom in the satellite imagery, and see how close enough yo can see the image for high satellite imagery resolution. The high satellite imagery resolution will be vary place to place depends on the image availability from google. So not every place will have the same resolution. For example in figure 5, wen can see the high resolution satellite imagery of Treasure Island California.

Google Satellite Imagery Layer
Figure 4. Google Satellite Imagery Layer
Figure 5. Treasure Island satellite imagery from Google

How to Check the Date of Google Satellite Imagery

There is no direct way in QGIS to check the google satellite imagery date. But we can use google earth to do it. Open Google Earth, zoom in to the place of imagery you want to check, the imagery date can be seen at the bottom of google earth as in figure 6.
  
Checking Google Imagery date in Google Earth
Figure 6. Checking Google Imagery date in Google Earth

ESRI World Satellite Imagery

The second way to add satellite imagery as a layer in QGIS is using ESRI World Imagery, which is provided in ESRI ArcGIS online. It serves as ArcGIS REST API service. To add the service can be used a tool called Add ArcGIS Map Server Layer. The tool can found at menu Layer >>  Add Layer >> Add ArcGIS Map Server Layer... as in figure 7. The satellite imagery from ESRI can be seen as in figure 8. The date of satellite imagery can be checked using Identify feature tool in QGIS. See how to use ArcGIS REST API Service for complete tutorial.

Add ArcGIS Map Server Layer tool in QGIS
Figure 7. Add ArcGIS Map Server Layer tool in QGIS

Treasure Island satellite imagery from ESRI ArcGIS REST API
Figure 8. Treasure Island satellite imagery from ESRI ArcGIS REST API


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