hi:soil moisture mappin using grads,doubts plz clarify

[smita]

Hi everyone,

  I am smita , and i just joined the grads user group.

  I am using grads for the first time, and i am bit confused regarding .ctl file

  I am workin on  a project which maps brightness values[tb] over required region for Ascending and Descending passes of satellite carrying passive microwave radiometer
  as the satellite advances it gathers tb values.

  For the ascending pass[when satellite moves frm south to north] and descending[north to south] we have different lat ,long values and corresponding tb values.

  I wrote a program which writes out in binary these 3 below values in this order.  lat                 lon               btd
  37.820000   97.650002   250.000000
 37.040001   93.779999   253.990005
 36.709999   95.540001   254.320007 ----- [sample values how they look like in asci]
 -7.450000   6.810000     155.949997
 -7.760000   5.370000     320.000000
    -9.310000  -1.820000   320.000000

  i dont have any level or time data. i dont need them rather.so i didnt print them in binary file.

  sample  i wrote is

     DSET output.txt--------------------------[this is binary file]
  TITLE Sample Data Set
  UNDEF -9.99E33
  XDEF 100 LINEAR 1 1
   YDEF 100 LINEAR 1 1
  ZDEF 1 LINEAR 1 1
   TDEF 1 LINEAR 1JAN2000 1DY
  VARS 1
  btd 0 99 brightness value
  ENDVARS



My doubts
   1. When i am giving it as btd it says undefined variable.How do i make it read btd values frm the binary file and map them accordin to the required lat and long values.

  2. Is the lat and longitude mapping accordin to the output.txt i am givin or, just taking range of lat and long values as mentioned by xdef and ydef.

  3. Shuld the binary data contain,the data in order of longitude,latitude,level ,variable and time. and if we dont have any level or time data ,is it enough to take them as single value in .ctl file if not as some constant value in binary file.

  Any help in tellin how to write the  data descriptor file would be greatly appreciated.

  regards
  smitha



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