Piertopier.net provides free wireless internet access to Brighton beach, using WiFi (IEEE 802.11b) technologies. With a WiFi card in your laptop, or a Mac with Apple's airport capabilities, you can connect to the internet for free from the beach, when in range of their nodes. Amplicon is proud to sponsor PierToPier, and help provide a technical solution that remotely monitors local weather in real-time.
The weather information provided by PierToPier is the sum of many parts
A wind sensor, kindly donated by Amplicon Liveline
A Moxa NPort 4511 Programmable Communication Gateway, also donated by Amplicon Liveline
Some custom software running on the NPort
PierToPier nodes 1 and 2
MRTG graphing software
It all fits together as shown below in the diagram:
Sequence of events is as follows:
1. Hot air rises and cold air falls, thus causing it to be windy on the beach
2. The wind is picked up by the wind sensor, which constantly outputs wind speed and direction in NMEA-0183 format on its RS-422 interface
3. The NMEA data are received by the NPort 4511's serial (RS232/422/485) port, where the custom code computes the average wind speed so far and records the wind direction and gust speed. The custom code also implements an SNMP agent, which is constantly listening for queries. For this application, SNMP is the means by which information is retrieved from the NPort 4511 via its Ethernet port
4. Meanwhile, MRTG is running on the PierToPier webserver; MRTG is a piece of free software that builds graphs based on values fetched by SNMP queries. Every five minutes, it sends an SNMP query to the NPort 4511's Ethernet port to ask the custom code for wind direction, speed, and gust readings. This query makes its way over the Internet to PierToPier node 1, and then to the NPort 4511 via the wireless link between Nodes 1 and 2
5. The custom code on the NPort 4511 receives the SNMP query and formulates a reply. After the reply is sent back to MRTG, the maximum gust speed is set to zero, and the process of computing the average wind speed is begun again
6. After receiving the SNMP reply, MRTG updates its graphs, which are then made available on the PierToPier webserver
7. Further post-processing occurs to produce the XML Feed - this can be retrieved from the PierToPier webserver by anyone for their own use. For example, the Brighton Sailing Club use the XML feed to build their own weather page.