This content shows how to make a color composite in QGIS. The case study was flood disaster in Vietnam in 2017.

1. Center for Research and Application for Satellite Remote Sensing
Yamaguchi University
Color Composite in QGIS
Case Study: Flood in Vietnam

2. • According to the Quick report on Aug 25th 2017 from Standing office of Central Steering
Committee for Natural Disaster Prevention and Control (CSCNDPC). The storm number 6 name
Hato had landing on Hong Kong, China. On land, the storm also affected to the province in the
Northern of Vietnam. There are a lot of heavy rain, land slide and local flood in mountain area.
• According to the rapid report of the affected provinces (Ha Giang, Yen Bai, Tuyen Quang, Thai
Nguyen, Lang Son, Bac Can), the situation and Initial damage caused by Storm number 6 are as
follows:
- Casualty: 02 people dead, 01 people missing,
- Housing: 05 houses collapsed completely; 387 unroofed;
- Agriculture: Total area of rice and crops are flooded: 1.751 ha, including 1.502 hectares of rice
and 249 hectares of crops.
• http://phongchongthientai.vn/tin-tuc/bao-cao-nhanh-cong-tac-truc-ban-pctt-ngay-25-8-2017/-c5174.html
• http://www.nchmf.gov.vn/web/vi-VN/104/51/5594/Default.aspx
Vietnam Flood in 2017

3. ALOS2 level data and processing
Product from Sentinel ASIA website
• Jpeg
• GeoTiff
Product from JAXA (CEOS SAR/GeoTIFF)
• Level 1.1 This is complex number data on the slant range following compression of the range and azimuth. As one-look data,
it includes phase information and will be the basis for later processing. In wide-area mode, image files are created for each
scan.
• Level 1.5 This is multi-look data on the slant range from map projection amplitude data, with range and azimuth compressed.
• Level 2.1 Geometrically corrected (orthorectified) data using the digital elevation data from Level 1.1
• Level 3.1 Image quality-corrected (noise removed, dynamic range compressed) data from Level 1.5
https://sentinel.tksc.jaxa.jp/sentinel2/emobSelect.jsp

4. • Image before flood : JPJXisis0001201708310012.tiff
• Date : 07 June 2017
• Image during flood : JPJXisis0001201708310011.tiff
• Date : 30 August 2017
• Software : QGIS
ALOS2 level data and processing

5. Open QGIS software🡪 add raster layers

6. Raster 🡪 Miscellaneous 🡪 Merge

7. A false color composite is created, with two of the RGB bands on
the "during" image and one on the "before"
Red : SAR Image before flood
Green : SAR Image during flood
Blue : SAR Image during flood
Color composite for detecting flood

8. Merge later 🡪 right click at properties 🡪 red present as flood or wetland

9. Save RGB composite image: Right click at image 🡪 click “save as”

10. Save RGB composite image 🡪 Select “Rendered image” for output mode 🡪
Define directory and output file name

11. Open Google Earth 🡪 click “File” 🡪 click “Open”🡪 select “All files” for all formats

12. Open RGB image in Google Earth by create super overlay

13. Choose directory where the file should be saved. Then, wait for importing image data

14. Observe flood area (red color) in Google Earth
Google Earth
Analyzed result
(Red color is possible to be flood area)