[ncl-talk] hdf confusion
Marston Johnston
shejo284 at gmail.com
Tue Jun 13 15:14:47 MDT 2017
Here’s a NCL page dedicated to the handling of HDF files used by satellites such as MODIS.
https://www.ncl.ucar.edu/Applications/HDF.shtml
/M
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Marston S. Johnston, PhD
Department of Earth Sciences
University of Gothenburg, Sweden
Email: marston.johnston at gu.se
SkypeID: marston.johnston
Phone: +46-31-7864901
Only the fruitful thing is true!
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
From: Michael Notaro <mnotaro at wisc.edu>
Date: Tuesday, 13 June 2017 at 22:46
To: Marston Johnston <shejo284 at gmail.com>, "ncl-talk at ucar.edu" <ncl-talk at ucar.edu>
Subject: Re: [ncl-talk] hdf confusion
Thanks. I tried the following and only end up with a 2d grid of values like 2066, 18709, etc.
How can I retrieve slot [11-13] land/water flag with values like 000, 001, 010, etc?
Michael
aa=addfile("h10v04_yellowstone/MOD13Q1.A2012001.h10v04.006.2015236172021.hdf.hdfeos","r")
lat2d=doubletofloat(aa->GridLat_MODIS_Grid_16DAY_250m_500m_VI(::-1,:))
lon2d=doubletofloat(aa->GridLon_MODIS_Grid_16DAY_250m_500m_VI(::-1,:))
lat2d!0="nlat"
lat2d!1="nlon"
lon2d!0="nlat"
lon2d!1="nlon"
land=short2flt_hdf(aa->250m_16_days_VI_Quality_MODIS_Grid_16DAY_250m_500m_VI)
print(land)
Michael Notaro
Associate Director
Nelson Institute Center for Climatic Research
University of Wisconsin-Madison
Phone: (608) 261-1503
Email: mnotaro at wisc.edu
From: Marston Johnston <shejo284 at gmail.com>
Sent: Tuesday, June 13, 2017 3:37 PM
To: Michael Notaro; ncl-talk at ucar.edu
Subject: Re: [ncl-talk] hdf confusion
Hi,
Try this function: http://www.ncl.ucar.edu/Document/Functions/Contributed/short2flt_hdf.shtml
short2flt_hdf - ncl.ucar.edu
www.ncl.ucar.edu
NCL Home > Documentation > Functions > Type converters short2flt_hdf. Converts values of type short to values of type float using the "scale" and "offset" attributes ...
/M
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Marston S. Johnston, PhD
Department of Earth Sciences
University of Gothenburg, Sweden
Email: marston.johnston at gu.se
SkypeID: marston.johnston
Phone: +46-31-7864901
Only the fruitful thing is true!
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
From: <ncl-talk-bounces at ucar.edu> on behalf of Michael Notaro <mnotaro at wisc.edu>
Date: Tuesday, 13 June 2017 at 22:33
To: "ncl-talk at ucar.edu" <ncl-talk at ucar.edu>
Subject: [ncl-talk] hdf confusion
Sorry for the ignorant question but I am having trouble figuring out
how to properly retrieve the land-lake-ocean mask off this MODIS hdf file.
If I ncl_filedump *hdf, it shows the variable as ushort. If I ncl_filedump *hdf.hdfeos,
it shows the variable as short. Which should I use in addfile and how do I
retrieve the values of 001=land, 000=ocean, etc?
Michael
ncl_filedump h10v04_yellowstone/MOD13Q1.A2012001.h10v04.006.2015236172021.hdf.hdfeos
short 250m_16_days_VI_Quality_MODIS_Grid_16DAY_250m_500m_VI ( YDim_MODIS_Grid_16DAY_250m_500m_VI, XDim_MODIS_Grid_16DAY_250m_500m_VI )
coordinates :
GridLat_MODIS_Grid_16DAY_250m_500m_VI, GridLon_MODIS_Grid_16DAY_250m_500m_VI
hdfeos_name :
250m 16 days VI Quality
projection :
Sinusoidal
unsigned :
True
Legend :
Bit Fields Description (Right to Left):
[0-1] : MODLAND_QA [2 bit range]
00: VI produced, good quality
01: VI produced, but check other QA
10: Pixel produced, but most probably cloudy
11: Pixel not produced due to other reasons than clouds
[2-5] : VI usefulness [4 bit range]
0000: Highest quality
0001: Lower quality
0010..1010: Decreasing quality
1100: Lowest quality
1101: Quality so low that it is not useful
1110: L1B data faulty
1111: Not useful for any other reason/not processed
[6-7] : Aerosol quantity [2 bit range]
00: Climatology
01: Low
10: Average
11: High (11)
[8] : Adjacent cloud detected; [1 bit range]
1: Yes
0: No
[9] : Atmosphere BRDF correction performed [1 bit range]
1: Yes
0: No
[10] : Mixed clouds [1 bit range]
1: Yes
0: No
[11-13] : Land/Water Flag [3 bit range]
000: Shallow ocean
001: Land (Nothing else but land)
010: Ocean coastlines and lake shorelines
011: Shallow inland water
100: Ephemeral water
101: Deep inland water
110: Moderate or continental ocean
111: Deep ocean
[14] : Possible snow/ice [1 bit range]
1: Yes
0: No
[15] : Possible shadow [1 bit range]
1: Yes
0: No
_FillValue :
-1
valid_range :
( 0, -2 )
units :
bit field
long_name :
250m 16 days VI Quality
ncl_filedump h10v04_yellowstone/MOD13Q1.A2012001.h10v04.006.2015236172021.hdf
ushort 250m_16_days_VI_Quality ( YDim_MODIS_Grid_16DAY_250m_500m_VI, XDim_MODIS_Grid_16DAY_250m_500m_VI )
long_name :
250m 16 days VI Quality
units :
bit field
valid_range :
( 0, 65534 )
_FillValue :
65535
Legend :
Bit Fields Description (Right to Left):
[0-1] : MODLAND_QA [2 bit range]
00: VI produced, good quality
01: VI produced, but check other QA
10: Pixel produced, but most probably cloudy
11: Pixel not produced due to other reasons than clouds
[2-5] : VI usefulness [4 bit range]
0000: Highest quality
0001: Lower quality
0010..1010: Decreasing quality
1100: Lowest quality
1101: Quality so low that it is not useful
1110: L1B data faulty
1111: Not useful for any other reason/not processed
[6-7] : Aerosol quantity [2 bit range]
00: Climatology
01: Low
10: Average
11: High (11)
[8] : Adjacent cloud detected; [1 bit range]
1: Yes
0: No
[9] : Atmosphere BRDF correction performed [1 bit range]
1: Yes
0: No
[10] : Mixed clouds [1 bit range]
1: Yes
0: No
[11-13] : Land/Water Flag [3 bit range]
000: Shallow ocean
001: Land (Nothing else but land)
010: Ocean coastlines and lake shorelines
011: Shallow inland water
100: Ephemeral water
101: Deep inland water
110: Moderate or continental ocean
111: Deep ocean
[14] : Possible snow/ice [1 bit range]
1: Yes
0: No
[15] : Possible shadow [1 bit range]
1: Yes
0: No
hdf_name :
250m 16 days VI Quality
Michael Notaro
Associate Director
Nelson Institute Center for Climatic Research
University of Wisconsin-Madison
Phone: (608) 261-1503
Email: mnotaro at wisc.edu
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