Aggregate Example
A pressure sensor takes 40 readings over a user-defined ten minute interval. At the end of every interval, the sensor records the average of the 40 readings.
Glossary
Explore terms relevant to Dendra management and usage.
Access Level
Section titled “Access Level”The permissions required for a given User to access datasets. An Organization can restrict certain activity from users based on their user type and/or individual permissions.
| User Type | Definition |
|---|---|
| Public User | No affiliation to an organization. May or may not have a Dendra login. |
| Organization Member | A user with a login affiliated with an organization. |
The permission types in order, with each level including the former, are Hidden → Viewing Metadata → Charting Data → Downloading Data.
Aggregate
Section titled “Aggregate”Data loggers automatically record data in intervals. Common intervals are 1, 5, 10, 15, 30 minutes, and 1 hour. Most loggers, however, take readings at a much faster rate, such as every 15 seconds and store those readings in temporary memory.
An aggregate is the way those readings are aggregated, or combined, into the final reading of a User-defined interval that is stored into a permanent record.
| Aggregate Type | Definition |
|---|---|
| Average/Mean | The sum of all data reading values divided by the total number of readings within an interval. |
| Minimum | The minimum value found within a single interval. |
| Maximum | The maximum value found within a single interval. |
| Sample | The most recent reading of the datalogger. |
| Standard Deviation | Variability or dispersion of data readings in relation to the average/mean. |
| Sum | Total of all reading values within a single interval. |
| Cumulative Sum | The sum of multiple intervals. |
Also called Notification.
Managers can create alerts based on specific custom criteria. They can also activate Out of Spec alerts, which will check the equipment library and see if the instrument is reporting data outside of its operational parameters.
Dendra has a default alert State Offline that will send a notification if battery voltage has not been received from a station after an organization-specified amount of time (see Station Offline Threshold). The default is 24 hours.
Annotation
Section titled “Annotation”Also called Incident Report.
A dynamic data cleaning function. They allow a manager to
- Describe an event that occurred that affected a station or individual datastreams.
- Add a photo.
- Apply a data-cleaning action, such as:
- Exclude the (bad) data
- Apply an equation to correct the data
- Change an operational parameter, such as cable length or height of sensor
- No action (the annotation is is just a record of an event with not action required)
Comma Separated Value.
A text-based method of storing tables of data. The most common export format for time-series data.
Communication
Section titled “Communication”Also called Telemetry.
Any method of providing machine-to-machine communication to a Datalogger.
Common types include
- Cellular
- WiFi
- Satellite
- LoRaWAN
Dendra
Section titled “Dendra”This platform.
The name Dendra is derived from dendritic networks, i.e. networks where many small paths aggregate into central major paths, such as the roots of a treet into the trunk or capillary blood vessels into major arteries. It represents the flow of information from environmental monitoring equipment into a single, usable datastet.
Deployment
Section titled “Deployment”The time frame during which Equipment is put out for use. By default, something will be deployed at a date, then it is considered active until the deployment is ended. If a station is moved to a new site, the old deployment should be closed, and a new deployment referencing the new site should be created.
Datalogger
Section titled “Datalogger”A small, rugged, outdoor computer designed to have sensors attached to it, often equipped with real-time clocks to manage timestamps.
Datastream
Section titled “Datastream”A datastream is a Measurement, performed at a particular Site (x, y, z), using a particular method of measurement. A datastream can also be a manual measurement using a specific protocol, as long as it is performed at a particular site and a timestamp is recorded.
Datastream Example
Wind Speed at Cahto Peak using an R.M. Young 05103 Anemometer.
Note: Wind Direction is a separate datastream. The instrument is not the same as the datastream.
Daylight Savings Time.
Dendra ignores DST. All timestamps are timezone aware but adhere to standard time. UTC is used internally, but because monitoring captures diurnal processes, we ensure the local timezone is used. DST, on the other hand, causes problems when it jumps forward or backwards and has no value.
Equation Library
Section titled “Equation Library”Dendra has extensive support for derived datastreams, which can use raw datastreams or combine multiple datastreams into a single derived datastream, e.g. absolute humidty or correcting a sealed pressure transducer with barometric pressure. Dendra can also provide more abstract derived datasets, such as heat index.
Equipment
Section titled “Equipment”Dendra defines equipment as a Thing Type, as per Internet of Things (IoT).
It is a
- Sensor device
- Datalogger
- Communication device
- Any item used in support of the sensors and dataloggers
Equipment Library
Section titled “Equipment Library”The Equipment Library is a collection of information on all devices used within Dendra. The library provides pictures of the equipment, a web page, and the manufacturer. We also archive user manuals, including ones for discontinued equipment. We characterize tolerance limits for the sensors as best we can, so automated alerts can leverage them. The library also defines the Measurement, Variable, and Medium of sensors. It is also where practical Units are defined.
External Link
Section titled “External Link”A web address (URL) outside of Denda.
External References
Section titled “External References”Any Metadata that a manager desires to storein Dendra that is not currently part of Dendra’s metadata.
Geosensitivity
Section titled “Geosensitivity”Endangered species, especially plants, are at risk of being harmed if their location is published.
While monitoring equipment is at a lower risk, we provide a mechanism based on GBIF standards for location fuzzing to protect the exact location of your equipment.
Geostationary Operational Environmental Satellites.
GOES is a collaborative NOAA and NASA program providing continuous imagery and data on atmospheric conditions and solar activity (space weather).
NASA builds and launches the GOES and NOAA operates them. In addition to imagery, the GOES satellites serve as communications satellites for monitoring equipment.
If you have a GOES modem and a NOAA authorized timeslot, you can transmit from remote locations where there is no cellular or WiFi. That data is managed at the NOAA DCS server. Modem timeslots are assigned an alphanumeric code.
Example Timeslot
BEC0102AHOBOlink
Section titled “HOBOlink”Renamed to LI-COR Cloud.
The company LI-COR bought Onset Computing, which created the famous HOBO logger — a staple of field scientists. HOBOlink is their proprietary service for retrieving data from networked HOBO loggers.
Inherited
Section titled “Inherited”Dendra uses a simple hierarchical structure for its Metadata. If you see inherited, it means the values for that setting have been inherited from the parent item.
The basic hierarchy is: Organization → Station/Site → Datastream.
Integration
Section titled “Integration”Dendra orchestrates between multiple proprietary commercial venders. These are called integrations. A Station manager will use an integration to define where their data is coming from. Each integration requires certain information specific to that kind of connection to authenticate Dendra and allow it to pull data.
Example Integrations
Internet of Things.
A phrase used to describe small, highly networked devices with specific functions, such as parking meters, automatic lighting, smart houses, or single function sensors. Some effort has been made to create an Internet of Nature, using similar methods. The natural environment is challenging, and so far the adoption has been slower. LoRaWAN is one product of IoT that has seen significant adoption.
LoggerNet
Section titled “LoggerNet”Campbell Scientific, one of the major datalogger and sensor manufacturers, provides a proprietary software platform for accessing its loggers and retrieving data. This is LoggerNet. Dendra can provide containerized versions of LoggerNet for any organization that has a license. If the organization already has an operational server, that can be used instead.
LoRaSAT
Section titled “LoRaSAT”Long Range Satellite.
Low earth satellites, cubesats, which allow low power, low speed transmissions from small modems. SWARM was the first company to achieve loraSAT, but it was acquired by SpaceX and shut down.
LoRaWAN
Section titled “LoRaWAN”Long Range Wide Area Newtwork.
LoRaWAN is a newer form of low power, low speed communications popularized by IoT. It has the advantage of requiring significantly less power than WiFi and operates at lower frequencies allowing it to transmit through vegetation.
Its primary downside is lower data rates, which reduces its value for video, sound, or image transmission.
Measurement
Section titled “Measurement”Also often referred to as Variable.
A measurement is a term within a controlled vocabulary that describes what a sensor is measuring. New sensors are always being created.
Medium
Section titled “Medium”A medium is what is being measured by a sensor.
Example Mediums
| Measurement | Medium |
|---|---|
| Air Temperature | Air |
| Stream Stage | Surface Water |
| Fuel Moisture | Wood Tissue |
Metadata
Section titled “Metadata”Information that describes supporting data and instruments that create the primary data.
Example Metadata
Wind speed is a Measurement. An example wind speed datapoint would be 11.3 meters per second.
Metadata about the wind speed would be
- Units (
meters per second) - Instrument (
R.M. Young Anemometer 05103) - Height of the instrument from the ground and its geographic location (
lat,long,elevation).
Organization
Section titled “Organization”The group that is managing instrumentation in the field or performing Measurements. This can be an institution (e.g. University of California Nature), or it can be a project (e.g. The Fog Research Networks and Sites).
Organization is the highest level in Dendra’s hierarchy of information (see Access Level). Stations must belong to an organization. Datastreams must belong to a station.
Output Field
Section titled “Output Field”See Datastream.
Dataloggers store Measurements at intervals, such as once every 10 minutes, but they take measurements at a much higher interval, such as every 15 seconds. The data gets stored in multiple fields in a table depending on the Aggregate used. The datastream is actually an array of datasets from multiple fields that pertain to the same measurement event, but are different aggregates.
Example Output Field
Air temperature will have min, max, average, standard deviation, and possibly sample (one reading) within its output field.
Some custom instruments will use output fields for unique Purposes.
Example Custom Output Field
An Acoustic Doppler Current Profiler (ADCP) will have distances for each output field and all fields will have the same value (instantaneous velocity).
Purpose
Section titled “Purpose”This is a Dendra-specific term referring to how a User should regard a Datastream. There are three options:
| Purpose | Meaning |
|---|---|
ReadytoUse | The datastream is already in geophysical units and is well enough defined to be used as is. |
Raw | The data may be in non-geophysical Units, such as amps, volts, or milliseconds, or it may require processing to result in a usable measurement. Raw data can be filtered out so you can find ReadytoUse data. |
StatusInformation | Some datastreams are not about Measurements. They are about the condition of the sensor. StatusInformation confirms the data is worth using. StatusInformation can be filtered out so you cna find ReadyoUse data. |
Resources
Section titled “Resources”Stations allow the uploading of files to supplement information about the station. These can be spec sheets, audit reports, stream ratings curves, etc.
Actively editable proprietary formats, such as Excel or Word documents are discouraged.
Sample Interval
Section titled “Sample Interval”The time between the storing of data on a Datalogger. Intervals generally span from 1 minute to 1 hour. Eddy flux towers can be much higher. Common logger intervals are 5, 10, and 15 minutes.
A site is simply a point location. It has a name, latitude, longitude, and elevation. It is not part of an Organization, and it does not have permissions or access levels.
Station
Section titled “Station”A station is a Datalogger with power at a Site. A station has sensors which make Datastream Measurements. Ideally, stations are networked.
In Dendra’s hierarchy of Metadata, stations inherit from Organization and are parent to datastreams (see Inherited).
Station Offline Threshold
Section titled “Station Offline Threshold”The amount of time Dendra will wait before sending an Organization an Alert to notify them that a Station’s battery voltage has not been retrieved. This is a status function helping alert managers to issues of network and power problems.
Telemetry
Section titled “Telemetry”See Communication.
The Things Network.
TTN is a company that provides tranmission services through LoRaWAN networks for IoT devices.
Thing Type
Section titled “Thing Type”See Equipment.
Dendra operates on timestamps. Internally, Dendra uses InfluxDB, a specialized time-series database, and stores time in UTC, with ISO 8601 format.
Example
2026-04-10T16:48:00.000Z, where Z indicates UTC.
Timestamp
Section titled “Timestamp”see Time.
Dendra recognizes two sets of Measurement: SI units, also known as the metric system, and imperial units, or British units. SI units are default as they are the scientific standard.
Uniform Resource Locator.
A website address.
Coordinated Universal Time.
UTC is the modern term for Greenwich Mean Time. Dendra uses UTC internally for all time data stored. It preserves timezone as Metadata and adds it to time when delivering data.
If you are reading this, you are probably are a user.
Anyone with an account is a user of Dendra. Even if you do not have an account, but you search and download data, you are a user.
If you have an account, your user profile can be associated with one ore more Organizations and be given additional permissions and roles (see Access Level).
Variable
Section titled “Variable”See Measurement.
Vocabulary
Section titled “Vocabulary”Dendra uses controlled vocabularies, or lists of terms that are restricted in order to keep consistency between users and Organizations and allow easier discovery of datasets.
It is not uncommon for a more general term to be used in a dataset, despite more specific terms existing. Again, this is for discovery purposes, and the Datastream itself usually will define the non-controlled specific term.
Example
Net Solar Radiation may resolve to Outgoing Longwave Radiation.