Campbell Scientific HFP01 Open Path Eddy Covariance (OPEC) - Page 20

OPEC Open-Path Eddy-Covariance System seconds and nanoseconds since 0000 hrs, 1 Jan 1990. In the TOA5 format, the time stamp is a quoted string, similar to that used in Microsoft® Excel. In the Array Compatible CSV, time is reported as elements of the array, e.g., in the same format as the Campbell Scientific mixed array dataloggers. NOTE Campbell Scientific recommends the use of TOB1 file format. This file format can be readily read into third party post processing software, e.g., EdiRe or MatLab. If required, a TOB1 flux file can be converted into a TOA5 flux file using CardConvert. A TOA5 file is comma separated values and easily read into Microsoft® Excel as a CSV file. Both the TOB1 and TOA5 formats contain an ASCII header. This header contains information about the datalogger used to collect the data. The header also describes the data with variable names and units. For more information on the file formats, see Section 2.4 in the datalogger manual. For backwards compatibility with mixed array dataloggers, comma separated values, without header information, is also supported with LoggerNet and CardConvert. Elements that contain an array ID, day of year, hour and minutes, can be added to the first few columns of the data file. This format is supported in LoggerNet version 3.3 and CardConvert version 1.2 or greater. 4.1 Data Retrieval Data can be collected from a datalogger using both LoggerNet and a direct connection, or by physically moving the card from the datalogger to the computer. Using LoggerNet and a PC as a data retrieval option is only practical if the PC will be located at the site and is continuously polling the datalogger because the volume of data is such that it takes about 8% to 25% of real time to download 10 Hz time series data. Transferring data using the PC/CF card is relatively fast; however, it does require manual intervention to manage the files. A 1024 Mbyte file (about 28 days of 10 Hz time series from a basic open-path eddy-covariance system) will take about 15 minutes to copy from the card to a PC hard drive. A basic Open-Path Eddy-Covariance system will collect about 40 Mbytes of 10 Hz time series data per day. A strategy for maintaining manageable file sizes is to break them up into smaller files that cover time periods ranging from 1 hour to 1 day. This can be achieved with LoggerNet and the Baler, or using CardConvert. Both the Baler and CardConvert support naming these smaller files using the time stamp of the first record in the file. TIP A group file renaming utility can be useful to manage files from multiple stations. These utilities are commonly used in the photography industry to manage image files and are readily available on the web, ranging from freeware, shareware, and commercial versions. Any one of these will meet the data file management needs, as long as it can find and replace text within a file name. 12