Central California Ozone Study (CCOS) - Desert Research Institute

CCOS Field Operations Plan (DRAFT) Version 2: 5/31/00
2.4.8 Data Acquisition and Review
In general, data acquisition at existing sites consists of an onsite data logger to collect and
average data, which are automatically transferred to a central computer through a telephone
modem. The transfers can be as often as once an hour. Each time the site is polled, new data are
appended to the data file for that site.
CCOS supplemental data will be obtained in a similar manner through data loggers that
will be installed at the sites. A central CCOS computer located at DRI in Reno will be
configured to call the sites once a day to obtain supplementary CCOS data. The calling times
will be set so as not to interfere with site operations. In addition, the district data will be
uploaded as well. Collection and screening of the district data will ensure the highest level of
data completeness and will provide a complete picture of what is happening at all CCOS sites in
near real time. These data also will be useful in supplementing forecast information.
Since there are over five different agencies involved in data collection, the manner in
which the data are obtained may vary. Obtaining the data within 24 hours of collection will be a
priority. One method will be to call the district data logger during a designated window and
obtain the data directly. Another method is for the agency to transfer their data to an accessible
file transfer protocol (FTP) computer daily and then the CCOS computer downloads data from
the FTP site(s).
Due to the variability in formats of the district data, this portion of the data acquisition
system will require the greatest amount of preparation. Information will need to be gathered for
each site on: acquisition software, download windows, telephone numbers or FTP addresses and
directories, parameters collected (name, order, units, averaging times, time stamps, delimiters,
etc.), and calibration periods and target values.
Each morning new data collected by the central CCOS computer will be evaluated.
Several electronic reports will be generated during the evaluation and will be available to the
CCOS team on an area of the DRI network dedicated to the CCOS project. Each step in the
evaluation will be automated to the extent possible. These screening checks are designed to
catch a failure in a measurement system, which in turn triggers prompt corrective action to avoid
large data losses.
The first step in the evaluation will be to verify that all sites were polled successfully. A
simple error report will be generated that lists any sites where a connection was not made. Next,
a running table will be updated that lists the start and stop times of the data collected with any
gaps noted. Once the evaluation of data completeness is performed, simple statistics will be
calculated (e.g. mean, max, min, etc.) and archived. The values will be scanned for outliers and
if any are noted an error report will be generated.
Where feasible, rates of change and inter-parameter relationship checks will be calculated
(e.g. temperature values that change too rapidly during a two hour period, relationship between
ozone and NOY). The emphasis of rates of change checks will be applied with caution. Criteria
used for rates of change are often difficult to set properly due to the variability of conditions at
sites located in a large geographical region. If the criteria are set too narrow, unnecessary error
Chapter 2: FIELD MEASUREMENTS 2-33