Sorry if you've already provided these answers elsewhere. If so, please feel free to simply point me to that source of help information.
I'd like to confirm both the 5-min. & 1-hr. interval data's time conventions of 1.) imported NSRDB weather data, 2.) SAM's geometrical sun angle calculations, and 3.) exported output CSV data.
For each of the above #1-3: What are the time conventions (i.e., what does a given timestamp represent)?
A.) Beginning-of-interval (left-labeled),
B.) Middle-of-interval (center-labeled),
C.) End-of-interval (right-labeled),
D.) Exact timestamp-calculated; often, middle-of-interval timestamp-calculated (center-calculated), or
E.) Mixed (e.g., some variables left-labeled & others center-calculated)
More detailed descriptions of the above options:
A.) Beginning-of-interval (left-labeled):
1990-01-01 00:01:00 timestamp represents:
A1- 1990-01-01 00:01:00 – 1990-01-01 00:02:00 (1-hr data)
A2- 1990-01-01 00:01:00 – 1990-01-01 00:01:05 (5-min. data)
B.) Middle-of-interval (center-labeled):
1990-01-01 00:01:00 timestamp represents:
B1- 1990-01-01 00:00:30 – 1990-01-01 00:01:30 (1-hr data)
B2- 1990-01-01 00:00:58 (?) – 1990-01-01 00:01:03 (?) (5-min. data)
C.) End-of-interval (right-labeled):
1990-01-01 00:01:00 timestamp represents:
C1- 1990-01-01 00:00:00 – 1990-01-01 00:01:00 (1-hr data)
C2- 1990-01-01 00:00:55 – 1990-01-01 00:01:00 (5-min. data)
D.) Exact timestamp-calculated; often, middle-of-interval timestamp-calculated (center-calc'd)
1990-01-01 00:01:00 timestamp represents:
D1- Exactly at 1990-01-01 00:00:30 (1-hr data), or
D2- Exactly at 1990-01-01 00:01:00 (1-hr data), or
D3- Exactly at 1990-01-01 00:01:30 (1-hr data)
D4- Exactly at 1990-01-01 00:00:58 (?) (5-min. data), or
D5- Exactly at 1990-01-01 00:01:00 (5-min. data), or
D6- Exactly at 1990-01-01 00:01:03 (?) (5-min. data)
Or, E.) Some combination (mixture) of the above, e.g., where certain variables (not involving sun position calcs) are left-labeled (#A1 for 1-hr data, #A2 for 5-min. data) and others (involving sun position calcs) are exact timestamp-calculated (#D3 for 1-hr data, #D5 for 5-min. data).
I believe the SAM Help Menu says the imported & exported (output CSV) data (e.g., weather data) time convention is beginning-of-interval (left-labeled) (#A). However, do all the (calculated & exported) sun position-dependent variables represent "middle-of-interval timestamp-calculated" (#D)? e.g., For timestamp 1990-01-01 00:01:00, are POA irradiance & other sun position-dependent variables determined at exactly 1990-01-01 00:01:30 (#D3) for the hourly case, whereas other variables not involving geometrical sun position calculations (e.g., GHI, Tamb, Wspd) represent summed or averaged values & are reported as "beginning-of-interval" (#A1 for hourly)? What about for 5-min. data?
For 5-min. interval data, I think I read that, for timestamp 1990-01-01 00:01:00, sun position-dependent variables represent data calculated & reported at the exact (not necessarily middle, in this case, but perhaps an instantaneous "snapshot"?), recorded timestamp 1990-01-01 00:01:00 (#D5); whereas, other variables not involving sun position calcs represent summed or averaged values over 1990-01-01 00:01:00 to 1990-01-01 00:01:05 and are reported as beginning-of-interval (#A2). Would you please confirm if this is correct?
Many thanks.
