I would like to know the format for the "Decimal Year" input in the World Magnetic Model 2000 Block in the Aerospace Blockset 1.6.2 (R14SP2)?

I would like to dynamically update the date for the World Magnetic Model 2000 Block. I have checked the "Input decimal year" box in the mask, but I am not sure what the format for the incoming signal should be.

Answer 1

[MathWorks Support Team]

This change has been incorporated into the documentation in Release 14 Service Pack 3 (R14SP3). For previous releases, read below for any additional information:

We have verified that documentation on the "Decimal Year" input of the World Magnetic Model 2000 block is not entirely clear.

Here is some additional information on the format of the "Decimal Year" input: the input to the block should be the desired year in a decimal format to include any fraction of the year that has already passed. So the value is the current year plus the number of days that have passed in this year divided by 365.

The following code illustrates how to calculate the decimal year, "dyear", for March 21, 2005:

year = '2005';

year_selected = str2num(year);

month = 'March';

day = '21';

if (mod(year_selected,400)&&~mod(year_selected,100))

      % leapyear = false;

      ndays = 365;

elseif ~mod(year_selected,4)

      % leapyear = true;

      ndays = 366;

else 

      % leapyear = false;

      ndays = 365;

end

day_of_year = datenum([day '-' month '-' year])-datenum(['1-january-' year]);

dyear = year_selected + day_of_year/ndays;