Explanation of Matchup Process for In-Situ SeaBASS Data
Goal:
-
Match in-situ measurements based on latitude, longitude, date, and time
(Assuming measurements don't already match by unique 'Station-ID').
Approach:
- Design an IDL script that uses metadata from Chlorophyll files and matches that information to the accompanying AOP or IOP data.
The script is run twice: Once for the CHL & Rrs matches and again for the CHL & IOP matches.
These arrays are linked by a unique identifier that is assigned to the files before they are exported from the AOP/IOP Database.
- Differences in coordinates will generally not exceed 0.1 degrees in each direction and differences in time will not exceed 24 hours.
Of course, variations in coordinate buffering may occur for experiments near the poles where distances between coordinate grids decrease.
Other experiments, such as BBOP, may also associate AOPs and IOPs with chlorophyll measurements that were collected more than 24 hours later.
- Flags will be appended to the matchup set, which will identify these variations in time and location.
For example, a time-flag of 2 will indicate that the in-situ measurements were collected within 2 hours of one another.
A location-flag of 0.5 will indicate that the maximum distance from the orginal measurement was 0.5 degrees in each direction.
- Matchups are also unique. In other words, a reflectance value taken at a specifc location and time will be matched with a the most proximate chlorophyll and IOP measurement. Therefore, the same reflectance values will not be matched more than once.
Example:
