The very first step of your project will be to define the area you want to work on. This area is called the region of interest (ROI).
We will define our area of interest using a bounding box. To find the coordinates of a bounding box, check: bboxfinder
We will build a new shapefile containing the Region of Interest (ROI) from a set of coordinates.
Coordinates Reference System (CRS)
| Geographic CRS | Projected CRS |
|---|---|
| span the entire globe | localized to minimize visual distortion in a particular region |
| based on a spheroid | based on a plane (the spheroid projected onto a 2D surface) |
| angular units (degrees) | linear unites (meters) |
| lat / lon | X / Y |
| World Geodetic System 1984 (WGS 84) |
Universal Transverse Mercator (UTM) |
| EPSG:4326 | EPSG:32631 (in Belgium) |
In bboxfinder, you can easily switch from one CRS to another. As Sentinel images projected onto a WGS84/UTM grid, it is easier to get the coordinates of your ROI directly in WGS84/UTM.
It is important to set the EPSG code matching with the EPSG code of your satellite images!
For instance, if your ROI is located in Belgium,
- the CRS is WGS84 / UTM zone 31N
- the EPSG code is 32631
Coordinates bounding box
You can easily copy the coordinates of your bounding box via bboxfinder.
bbox = [627263.7,5596175.1,637115,5590485.2] # Paste the coordinates here
ulx = bbox[0] # Upper Left x
uly = bbox[1] # Upper Left y
lrx = bbox[2] # Lower Right x
lry = bbox[3] # Lower Right y
If you use QGIS 3, you have the ability to add Google Maps (maps, satellite, terrain) layers to your map. This tutorial shows you how.