水资源管理
A CR510 datalogger routinely measures water level and rainfallat a standard field site.
The goal of the Department of Resource Management is to ensurethe sustain-able use and protection of water resources for thebenefit of the people of the St. Johns River Water ManagementDistrict (SJRWMD) and the state of Florida. The departmenthas six divisions: Groundwater Programs, Hydrologic Data Services(HDS), Permit Data Services (PDS), Resource Management Support andEnvironmental Management, Water Supply Planning, and Water UseRegulation.
水资源管理
HDS collects, processes, manages, and disseminates hydrologicand meteorological data used for water use planning and management,environmental protection and restoration, and flood controlpurposes. The division operates and maintains more than 1,000monitoring stations throughout the district. It alsoprocesses data from approximately 200 additional sites collected bycounty and municipal agencies through mutual agreement or by theU.S. Geological Survey under contract to the district.
More than 7 million measurements are collected, verified,processed, and stored by HDS staff each year. The data isdisseminated to district staff and the public upon request. HDS also compiles the district’s Hydrologic Conditions Report,posted on the district’s Web site each month.
水资源管理
SJRWMD has set up a data acquisition network using CampbellScientific equipment to monitor rainfall and water level forbaseline data, water management, and flood control response andwarnings. The network uses over 370 Campbell Scientificdataloggers interrogated by four base stations that retrieve datato a central Hydstra database.
The district has three UHF licensed frequencies. Thedistrict headquarters in Palatka has two RF base stations. Each base station uses its own frequency—combined they poll 208stations. There are remote base stations at Apopka (68 sites)and Palm Bay (98 sites) to poll the remaining stations.
水资源管理
A broadcast Time Domain Multiple Access (TDMA) technique hasbeen used by Campbell Scientific since the early 1990s for networksrequiring high data throughput. The RF bandwidth is tightlycontrolled and optimized to move data from many data-loggers asefficiently as possible. This method allows for stand-alonerepeaters, and also allows datalogger measurement sites to act asrepeaters.
The technology focuses on measuring, storing, and transmittingaccurate time-stamped data. LoggerNet software rap-idlygathers real-time data as the highest priority, but in inactiveperiods collects any outstanding time-stamped historical dataallowing any “holes” in the data to be filled. Additionally,maintenance functions such as new program download, operatingsystem download to the datalogger, clock synchronization, andchanges to settings are performed during inactive periods.
水资源管理
The data is transferred in a master/slave configuration. At each poll interval, the RF base station (master radio)broadcasts a message to all dataloggers (slaves) that can bereached without using a repeater. Upon receiving thebroadcast, each datalogger sends its data at the pre-defined time;time windows can be less than one second. When sites areaccessed through a repeater, the repeater sends out a broadcast toits remotes that in turn respond with their data at predefinedtimes. The data is placed in packets and sent to the serverat the RF base station. There can be any number of repeaters;sites at St Johns are up to four deep in the network.
水资源管理
SJRWMD was pleased with the network performance during thesummer Hurricane season of 2004. The RF system workedflawlessly. There were problems with the Intranet provider,causing links to the two remote LoggerNet–RF base stations to belost. A redundancy has been designed into 16 of the mostcritical sites using CR510s and digital cell phones to provideredundant access to the data.
The original contract required Campbell Scientific to installthe first 20 sites and prove the technology. After training,the district installed the remainder of the sites. Onehundred additional RF telemetry sites are planned for 2006.