;
;  This example code illustrates how to access and visualize GPM L1B file
; in IDL. 
;
;  If you have any questions, suggestions, comments on this example, please 
; use the HDF-EOS Forum (http://hdfeos.org/forums). 
; 
;  If you would like to see an  example of any other NASA HDF/HDF-EOS data 
; product that is not listed in the HDF-EOS Comprehensive Examples page 
; (http://hdfeos.org/zoo), feel free to contact us at eoshelp@hdfgroup.org 
; or post it at the HDF-EOS Forum (http://hdfeos.org/forums).
;
; Usage:
;                               
; $idl 1B.GPM.GMI.TB2016.20160105-S230545-E003816.010538.V05A.HDF5.idl
;
; Tested under: IDL 8.6.0
; Last updated: 2018-01-22

; Open file.
file_name='1B.GPM.GMI.TB2016.20160105-S230545-E003816.010538.V05A.HDF5'
file_id=H5F_OPEN(file_name)


; Retrieve data.
datafield_name='/S1/Tb'
data_id=H5D_OPEN(file_id, datafield_name)
dataf=H5D_READ(data_id)

; Get '_FillValue' attribute.
fv_id=H5A_OPEN_NAME(data_id, '_FillValue')
fv=H5A_READ(fv_id)
H5A_CLOSE, fv_id

; Get 'units' attribute.
units_id=H5A_OPEN_NAME(data_id, 'units')
units=H5A_READ(units_id)
H5A_CLOSE, units_id

; Close dataset.
H5D_CLOSE, data_id

; Retrieve lat/lon.
lat_name='/S1/Latitude'
lat_id=H5D_OPEN(file_id, lat_name)
lat=H5D_READ(lat_id)
H5D_CLOSE, lat_id

lon_name='/S1/Longitude'
lon_id=H5D_OPEN(file_id, lon_name)
lon=H5D_READ(lon_id)
H5D_CLOSE, lon_id

; Close file.
H5F_CLOSE, file_id

; Process missing value, convert dataf that are equal to missingvaluef to NaN
idx = where(dataf eq fv, cnt)
if cnt gt 0 then dataf[idx] = !Values.F_NAN

; Subset at nchan1=0.
dataf = dataf[0,*,*]

; Compute data min/max for colorbar.
datamin=MIN(dataf, /NAN)
datamax=MAX(dataf, /NAN)
dim=SIZE(dataf,/dim)

long_name = datafield_name + ' (nchan1=0)'

; Generate the plot.
m = MAP('Geographic', TITLE=file_name, FONT_SIZE=9, /BUFFER)
ct = COLORTABLE(72, /reverse)
t1 = TEXT(0.1, 0.2, FONT_SIZE=8, long_name)
c1 = SCATTERPLOT(lon[*], lat[*], OVERPLOT=m, $
                 MAGNITUDE = dataf[*], $
                 RGB_TABLE=ct, $
                 POSITION=[0.1, 0.1, 0.83, 0.9],$
                 /SYM_FILLED, SYMBOL='o', SYM_SIZE=0.1)
mc = MAPCONTINENTS()
datamin=MIN(dataf)
datamax=MAX(dataf)
cb = COLORBAR(RGB_TABLE=ct, RANGE=[datamin, datamax], /BORDER, ORIENTATION=1, TEXTPOS=1, POSITION=[0.85,0.2,0.87,0.8], TITLE=units)
png = file_name + '.idl.png'
c1.save, png, HEIGHT=600, WIDTH=800
EXIT