View source for SAR flood mapping with SNAP

=Subsetting= 
We need to reduce the data volume by subsetting the large Sentinel-1 scenes.
* Activate the Rectangle Drawing Tool [[File:snap_box_drawing.png]]
* Left click and drag a rectangular box in the viewer to mark a subset area.
* Activate the selection tool [[File:snap_selection_tool.png]] and mark the box in the viewer.
* Right click '''WKT from Geometry'''.
* Copy the WKT string: CTRL + C.

[[File:snap_wkt_geometry.png|600px]]

* Open {{mitem|text=Tools --> GraphBuilder}}.
* Click {{button|text=Load}} and browse to the graph file ''\geodata_lokoja\01_lokoja_subset.xml'''
* Click on the '''Subset''' tab and activate '''Geographic Coordinates'''. 
* Paste the WKT string into the text field '''below''' the world map: CTRL + V.
* Check if the extent of the subset is displayed correctly onto the world map.
* Click {{button|text=Update}} to apply the box coordinates.

[[File:snap_subset_graph.png|600px]]

* Click the '''Write''' tab. Adjust the output directory to you local path.
* Click {{button|text=Run}}.
* Click the '''Read''' tab.
* Choose the pre-event Sentinel-1 source product (2018-04-01) from the drop down list.
* Click {{button|text=Run}}.
* Repeat the worksteps above creating a subset for the post-event image (2019-09-16).