Wihlo

Wihlo was created out of my frustration with the lack of a simple, good quality Linux weather station application for the Davis Vantage Pro2. At the moment Wihlo is still very much a work in progress, and as such is not ready for general use. Please keep checking back here for updates, or if you want further information please email [email protected]. In the meantime, you might be able to see a preview at http://prudhoe.wihlo.org or http://prudhoe.wihlo.org:5001

Features

• Display configurable weather graphs in a web browser
• Download data from a Vantage Pro2
• Import data from wview

Installation

Installation information will be gradually added here as I write it:

Create udev rule

In order to ensure a persistent serial device name, create a udev rule for the device as follows:

• Connect the VantagePro2 and then use dmesg to locate the device's idVendor and idProduct.
• Locate the device's serial number using the command udevadm info -a -n /dev/ttyUSB0 | grep '{serial}' | head -n1 (where ttyUSB0 is the device's name, also available from dmesg)
• Create a new udev rule by creating a new file in /etc/udev/rules.d called 40-vantagepro.rules with the following contents (replacing the values as appropriate): SUBSYSTEM=="tty", ATTRS{idVendor}=="10c4", ATTRS{idProduct}=="ea61", ATTRS{serial}=="1385229518", SYMLINK+="vantagepro2"

Dataloggers

This section lists any datalogger-specific notes. At the moment only the VantagePro2 is supported, but there are plans to add the Instromet dataloggers.

VantagePro2

Timezones

Wihlo stores all times in the database as UTC. However, the VantagePro2 gives readings in local times. Converting them into UTC can be difficult, when the timezone information is not fully known.

• If possible, it is recommended that you set the VP2 datalogger for a named timezone, not an offset from GMT, and keep this consistent. This is because the time field contained in a VP2 record is a local time, with no information as to its timezone.
• When downloading a set of records, Wihlo first asks the datalogger for its timezone. This information is used to convert the times of all the records received into a UTC time.
• If the timezone is a named timezone (as recommended), then this is used to compensate for DST, if required.
• If the timezone is simply an offset from GMT, then Wihlo queries the datalogger as to whether its internal clock is set to DST. If it is, then the time for each record is further adjusted to compensate. Therefore, when changing the local time on the VP2 to copmensate for DST, you should download all records before making the change, otherwise the time of the earlier records will be changed incorrectly for DST.
• Because the VP2 uses the local time in a download record, sometimes a record will contain exactly the same time as a previous record (if the clocks have gone back by an hour). Wihlo tries to spot this, by monitoring for times in records received during such "go back" hours: the first record received will be assumed to be in DST; Wihlo will jump to standard time once a record is received that has a time earlier than one already received.
• If importing from a wview database, it is assumed that the time in the wview database is already in UTC. It should be noted that wview calcuates UTC based on the local computer's timezone, not the timezone of the VP2 datalogger. Therefore, if the timezone on the computer that the VP2 is connected to is different to the timezone of the VP2 itself, then the times imported will probably be incorrect.

Migrating from wview

• The migration script assumes that the Wihlo database is empty, or that it does contain any readings for values being migrated. If existing readings do exist for the same times, then the migration will fail.
• Wview stores all measurements as US units in the database. Whilst this works well for most measurements (as the VantagePro2 transmits most in US), it doesn't work well for metric rain collectors. Therefore, for metric rain collectors, Wihlo will convert the measurements back to metric (it queries the datalogger o migration for the rain collector size). This means that if you have a metric rain collector, some data is recorded in metric, and some in US units.
• See above timezone section for notes about times migrated from wview