Measurements file

Data Files Format.

The data of solar diffused radiation measured by the spectrometer are stored in ASCII or Binary files.
The choice can be done setting the "Saving Mode" in the Options - Page 1.
During the developing and testing phase of the DAS the data were stored mainly in ASCII format, only after the installation of the equipment when the data acquisition became regular, the great amount of data suggested the switch to the binary saving mode.
In fact, each data file has a variable size, mainly due to the parameter that set the vertical binning of the CCD sensor (vb).
For ASCII files that means (256/vb) x 1054 * 2 bytes plus the spaces before and after each value for each spectrum stored).
In addition for each spectrum the ASCII Header with a fixed size of 166 bytes is stored. Fixing the vb to a value of 32, each file (containing 50 measured spectra) has a dimension of:
(256 / 32 * 1054 * 6 + 172) * 50 = 2478 KB.
In Binary mode the size of the Data file (with the same vertical Binning) is:
(256 / 32 * 1054 * 2 + 364) * 50 = 841 KB.

The dimension is quite smaller than the ASCII files even if the Binary Header. is greater than the ASCII one.

ASCII Header

Reading the ASCII header from left to right the following parameters can be identified:

• 1st record:
  1. station ( LOC: AAA)
  2. Latitude ( LAT: xx.xx)
  3. Longitude ( LON: xxx.xx)
  4. Altitude ( ALT [M/asl]: xxxxx)
  5. Zenithal solar angle ( SZA: xx.xx)
• 2nd record:
  1. Date (YYYY/MM/DD)
  2. Time (HH:MM:SS) - Local time considering also the DST - Daylight Saving Time
  3. Input mirror Position
  4. Spectral position
  5. Filter wheel position
  6. CCD Temperature (°C)
  7. Exposure time
  8. max value of the measure
  9. minimum of the measure
• 3rd record:
  1. Image type ( 0 = monochromatic, 1 = RGB),
  2. Value of the coordinated x beginning of the window of the CCD,
  3. Value of the coordinated y beginning of the window of the CCD,
  4. Value of the coordinated x end of the window of the CCD,
  5. Value of the coordinated y end of the window of the CCD,
  6. Value of the applieded vertical [binning] to the CCD,
  7. Line number of the measure
  8. Dummy
  9. Dummy
  10. Dummy
  11. Dummy
• 4th record: Character string to insert comments on the measures ( usable when DAS is manual mode).

Binary Header.

As the ASCII Header the binary one contains all the informations regarding the measures, but the values are stored in consecutives cells of memory, without the spaces necessary in the ASCII format.
The following table explains the format of the header in binary format.