Quick intro to satellite images & digital maps

Everyone knows Google Maps. Not everyone knows how to create your own map, draw your own contours, lines, and points with it. This video will introduce you to Google My Maps and guide you through (1) creating and editing your own data: points, lines, and contours (polygons); (2) delineating objects identified in satellite images; (3) sharing your map.

This video will explain you the concept of spatial data by importing a school list into Google My Maps from the Excel table. Google My Maps is an example of a simple online GIS (Geographic Information System). Key elements of the GIS software: map window, spatial data drawing/editing tools, measurement tools, layers panel. Layers – the key way to organize data in GIS. Creating and managing layers in Google My Maps.

This video will teach you saving you spatial data as a file. KML/KMZ-files as an example of the GIS-data exchange file formats. Importing your spatial data to another map or to other GIS systems.

Geographic coordinates: latitude and longitude. They are not linear but angular measurements! Where is the zero latitude and zero longitude? What is the diapason for possible values for the latitude and for the longitude? Coordinates units: degrees, minutes, and seconds. The GIS way for geographic coordinates: decimal degrees (DD). How to identify geographic coordinates of a given location with Google Maps?

For many areas Google Maps grants you access to the highly detailed images from a few top-level US satellites. What could we see in the satellite images in Google Maps? How various landscapes look like in the satellite images in Google Maps?

The Satellite View in Google Maps shows a mosaic of many different images and the boundaries can be difficult to understand. The date the images are taken is inconsistent and you cannot select the best time period for your studies. Information about the date and time of a particular image or study area is unavailable. At different levels of magnification, different satellite imagery is often used and can be outdated or inadequate. The level of detail they provide is inconsistent. Rural or remote areas are often only covered by low resolution images. Satellite images in Google Maps are presented in “natural colors”, which means valuable part of the information is lost.

Google Earth Pro as an example of a desktop geographic information system (GIS). How to install Google Earth Pro to your computer? The interface of the Google Earth Pro. How to import your KML/KMZ-files to Google Earth Pro? What additional information sources are available in Google Earth Pro? How to access multi-temporal imagery and do “time travels” in Google Earth Pro? How identify the exact date of the image you are looking at in in Google Earth Pro?

This video demonstrates how to create and edit your point, lines, and polygons in Google Earth Pro. Layers and your drawing (places) in Google Earth Pro. How to design and save your maps in Google Earth Pro. How to export your spatial data from Google Earth Pro as KML/KMZ-file(s).

Background imagery in the Global Forest Change portal – see the Earth in “false colors”. “False colors” visualize the invisible infrared light detected by sensors in Landsat satellites. How various landscapes look like in “false colors”.

Electromagnetic spectrum – we see only a small part of it but satellites could see more. Principles of the optical remote sensing. Landsat series satellites and their spectral bands. Various objects on the Earth’s surface reflect strongly or weakly at different wavelengths. You could choose any three bands, color them red, green, and blue, and combine into an RGB-image. Such images are called multispectral images. Multispectral images in Global Forest Change portal: 5-3-4 and 4-5-7 bands combinations.

This video will teach you how to find satellite data for your area of interest using Sentinel Hub EO Browser. Three simple steps to find the imagery you need: where, what, and when. Creating your own band combination and see your multispectral image. Saving it is a picture to your computer.

Step 1. Where: select the area of your interest. (A) Finding the area of your interest by name /address. (B) Finding the area of your interest by geographic coordinates. (C) Finding the area of your interest by importing the KML/KMZ-file you saved from Google Maps or Google Earth Pro.

The key features of each imagery type are (1) spatial resolution, (2) revisit time, and (3) data availability. Spatial resolution. Why lower spatial resolution is not always worse than higher? Revisit time. A compromise between spatial and temporal resolution. Data availability. What time periods are covered by various satellite data publicly available? Sentinel-2 satellite data – among the best freely available data from the EU satellites. Optical and radar images. Sentinel-1 is the only freely available radar satellite. “Time travels” with Sentinel Hub EO Browser. When an event was happened?

We cannot draw and export polygons and other vector data from the Sentinel Hub EO Browser. So, we cannot analyze images and create our own maps here. So we need to export the images from it. This video explains why the multispectral pictures you save from the Sentinel Hub EO Browser are NOT (yet) the spatial data. The spatial data (=GIS data) must be geo-referenced – connected with geographic coordinates. This is true not only for points, lines, and polygons (vector data) but also for satellite images (raster data). To export your image in the geo-referenced file format you must be registered in the Sentinel Hub and logged in. Exporting the images via Analytical Tab, choosing the KML/KMZ-format. Some other exchange file formats. Opening the exported geo-referenced satellite data in Google Earth Pro. Comparing them with the images available from Google.