Problems understanding MODIS LAI values

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isabelaugscheller
Posts: 1
Joined: Sun Jun 26, 2022 9:50 am America/New_York

Problems understanding MODIS LAI values

by isabelaugscheller » Sun Jun 26, 2022 10:06 am America/New_York

Hi there,
I haven't worked that much with remote sensing data yet and have a question regarding the MODIS FPAR/LAI data (MCD15A2H v006).
I downloaded the data with the R packages MODIStsp for my required time period and the appropriate section (West Africa) as GeoTIFF.

Unfortunately i don't really unterstand the values i get, when i open the raster files in QGIS or ArcGIS.
I will attach a picture of the values i get. Normally i would expect LAI to be in a range from 0 to 10 or something. Here i have values from 0 to 254. I already read the User Guide (https://lpdaac.usgs.gov/documents/624/MOD15_User_Guide_V6.pdf) where i found out, that some values refer to specific land use classes like:
250 = Urban
253 = Barren
254 = Water

But what about other values like 26 or something? Do i have to calculate the real LAI from these values? Or do you know how I can approach a 'normal' LAI value range from my results?
I already read a lot of papers regarding MODIS LAI but they never talk about such issues, the maps mostly have a value range from 0 to 7.

I would be very thankful if someone hat a tip or advice.

Isabel
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Bildschirmfoto 2022-06-26 um 15.56.38.png
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rapsodia86
Posts: 9
Joined: Wed Apr 13, 2022 11:58 am America/New_York

Re: Problems understanding MODIS LAI values

by rapsodia86 » Thu Jun 30, 2022 9:59 am America/New_York

Because LAI product is 8bit data type, values are from 0-255. Table 4 of the user guide you provided a link to, says that:
valid range is 0-100, fill values are 249-255, and multiply by scale factor=0.1.
So, mask/filter out values above 100 and multiply by 0.1.
Screenshot 2022-06-30 095645.png
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