Display of Chlorophyll-a Concentration

Update Jan 27, 2023

【Chlorophyll-a Concentration】
The concentration of the green pigment in phytoplankton insurface water.
(1) Conversion formula to observed value … Used on P.3 and P.8

physical quantity↓

Digital Number↓

Data_description = Chllorophyll-a concentration (CHLA) = DN * Slope + Offset [mg m^-3]↑
Slope

Offset = 0.0
Slope = 0.0016<HDFview>→ from image_data/CHLA
Attribute（metadata）↑OffsetPhysical Quantity（CHLA）＝Digital Number（DN）* 0.0016 + 0.01

Display of Chlorophyll-a Concentration（QGIS）

Dec 22, 2020

(2) Display using Log Sclae（1/5）① Convert CHLA data to GeoTIFF format.
> Convert with G-Portal (https://gportal.jaxa.jp/gpr/)> Convert with GDAL (https://shikisai.jaxa.jp/faq/faq0001.html)> Convert with Tool (https://shikisai.jaxa.jp/faq/faq0105.html)② Input to QGIS the converted GeoTIFF file

GC1SG1_202012130144D05610_L2SG_IWPRQ_2000

GC1SG1_202012130148H05611_L2SG_IWPRQ_2000

Ex： 2020/12/13 Path:56, Scene:10～112

Display of Chlorophyll-a Concentration（QGIS）

Dec 22, 2020

(2) Display using Log Sclae （2/5）③ Conversion to physical quantity
Shikisai Portal FAQ No.25
Use a “raster calculator”.
CHLA is recommended to be displayed on a logarithmic scale, so calculations here
use common logarithms.
< Reference >output file name(arbitrary)❷❶ Press “log10”❷ Click data (layer)❸ Press “＊”❹ input “0.0016”❺ Press “)”❻ Press “OK”

❸❶

❺

log10
( "GC1SG1_202012130144D05610_L2SG_IWPRQ_2000_0000000000195292_CHLA@1" * 0.0016 )❹❻3

Display of Chlorophyll-a Concentration（QGIS）

Dec 22, 2020

(2) Display using Log Sclae （3/5）④ Color correction
Set the display method, display range, and color tone.
Select the layer (scene) you want to set and open "Layer Properties".
❶❷

❸
❹

❺

❻

❶ Select “Single Band Pseudo Color”❷ Set the minimum value → Enter “-2.017”❸ Set maximum value → Enter “2.017”❹ Select “spectral” and “color bar inversion”❺ Set the color pallet❻ Check “Ignore out-of-range values”❼ Press “OK”
* Do this for the layer you want to display.

If you want to set the same settings for multiple layers,Settings can be saved and loaded❼
4Display of Chlorophyll-a Concentration（QGIS）(2) Display using Log Sclae （4/5）

Dec 22, 2020

⑤ Display of input/setting results
The operation results from ① to ④ are displayed. In the display range (-2.017 to2.017), high values (close to red) indicate locations with high chlorophyll-aconcentrations.

(Kanto - Tokai coast area)

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Display of Chlorophyll-a Concentration（QGIS）

Jan 8, 2021

(2) Display using Log Sclae （5/5）⑥ Contour
Select "Raster" > "Extract" > "Contour" from the menu.
Select the layer (①) for which you want to create the contour and execute.

❶Contour line layer creation result

Layer for which you want to create the contour

6

Display of Chlorophyll-a Concentration（QGIS）

Jan 27, 2023

(3) Display by physical quantity （1/4）① Convert CHLA data to GeoTIFF format.
> Convert with G-Portal (https://gportal.jaxa.jp/gpr/)> Convert with GDAL (https://shikisai.jaxa.jp/faq/faq0001.html)> Convert with Tool (https://shikisai.jaxa.jp/faq/faq0105.html)② Input to QGIS the converted GeoTIFF file

Ex： 2023/1/10 Path:68, Scene:10

GC1SG1_202301100224M06810_L2SG_IWPRQ_3000

7

Display of Chlorophyll-a Concentration（QGIS）

Jan 27, 2023

(3) Display by physical quantity （2/4）③ Conversion to physical quantity
Use a “raster calculator”.
Display settings using physical quantities are performed.
（[Ref] https://shikisai.jaxa.jp/faq/faq0128.html）
output file name(arbitrary)❶❶ Click data (layer)❷ Press “＊”❸ input “0.0016”❹ Press “OK”❷"GC1SG1_202301100224M06810_L2SG_IWPRQ_3000_CHLA@1" * 0.0016

❸

❹

8

Display of Chlorophyll-a Concentration（QGIS）

Jan 27, 2023

(2) Display by physical quantity （3/4）④ Color correction
Set the display method, display range, and color tone.
Select the layer (scene) you want to set and open "Layer Properties".

❶ Select “symbology”❷ Select “Single Band Pseudo Color❸ Select label setting file (*)❹ Check “Ignore out-of-range values❺ Press “OK”❷❶(*) [Label setting file] the FAQ "Please tell us thedisplay settings of the Shikisai images published on
JASMES. (https://shikisai.jaxa.jp/faq/faq0128_j.html)"
Please refer to the Excel available from
→ For chlorophyll-a concentration, edit and use thesheet "Palette_CHLA".

If you want to set the same settings for multiple layers,Settings can be saved and loaded❹❸<How to edit the Label setting file>1) Delete the first line (title)
2) Delete the last 3 lines (B, N, F)
3) Add "255" to column E4) Copy the contents of column A to column F5) Save with any file name in csv format → Go to ❸❺9Display of Chlorophyll-a Concentration（QGIS）(3) Display by physical quantity （4/4）

Jan 27, 2023

⑤ Display of input/setting results
The operation results from ① to ④ are displayed. In the display range (0 to 100),high values (close to red) indicate locations with high chlorophyll-a concentrations.

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