Field Alerts: Threshold, Drop, Imagery, and Weather

Field Alerts are the data-driven category inside Activity & Alerts. They fire automatically when satellite indices, imagery availability, or weather forecasts cross conditions you define, giving you hours or days of lead time over ground observation. Every field alert is produced by a rule card and flows into the same feed as task, map, scout, and system activity.

This page covers the four data-driven alert types and their configuration. For the full picture - task activity, scout escalations, delivery matrix, digests, and the unified feed - see Activity & Alerts.

Not sure what triggered your alert? Alerts tell you something changed. To decide what changed and what to do on a rice field, see Rice Diagnosis - a decision guide covering the three pillars of rice stress: abiotic (drought, salinity, poor soil, submergence), nutrient deficiency (N, P, K, Zn, S, iron toxicity), and biotic (diseases, insect pests, weeds).

Field Alert Types

NDVI Drop Alert

Triggers when NDVI falls by a defined amount between consecutive imagery acquisitions. Use this to catch rapid deterioration — crop disease, hail damage, or sudden drought stress — as soon as it registers in the data.

Threshold Alert

Triggers when any supported index (NDVI, NDRE, NDWI) crosses a value you set. Useful for monitoring slow-developing stress such as nutrient deficiency or prolonged waterlogging that approaches a critical level over several weeks.

New Imagery Alert

Notifies you the moment a new, cloud-free imagery acquisition is validated and available for a field. Use this when you are actively monitoring a disease outbreak or a recently applied treatment and need to know the instant fresh data arrives.

Weather Alert

Triggers on weather events detected at your field location: frost risk (temperature forecast below 0 °C within 48 hours), drought stress (consecutive days below 30% field capacity), or excessive rainfall (cumulative precipitation exceeding your defined threshold).

Creating an Alert

Open the Alerts tab

Navigate to Fields, select the field you want to monitor, and click the Alerts tab. Existing alerts for this field are listed with their current status.

Start a new alert

Click New Alert. The alert configuration panel opens.

Choose the alert type

Select one of the four alert types: NDVI Drop, Threshold, New Imagery, or Weather. The configuration fields update to match the selected type.

Set conditions

Configure the trigger conditions for your chosen type:

NDVI Drop — set the minimum drop magnitude (e.g., 0.15 between any two consecutive passes)
Threshold — select the index and the value it must cross (e.g., NDRE falls below 0.18)
New Imagery — no additional conditions; fires on every new validated acquisition
Weather — select the event type and set the numeric threshold if applicable

Choose delivery channels

Select one or more delivery methods: Email, SMS, or Webhook. You can combine all three for a single alert. See the Delivery Channels section below for setup details.

Save the alert

Click Save Alert. The alert activates immediately and begins evaluating conditions against every new imagery acquisition or weather update for this field.

Delivery Channels

Email
SMS
Webhook

Enter up to five email addresses per alert. Each address receives a formatted HTML email containing:

Alert name and field
Triggered condition and current index value
A thumbnail of the latest NDVI map with the affected area highlighted
A direct link to the field in the platform

Email addresses do not need to belong to platform users — you can notify agronomists, consultants, or farm managers who do not have a login.

Enter your endpoint URL. SemaiSens sends a POST request to that URL with a JSON payload every time the alert fires. Webhook delivery is ideal for integrating alerts into farm management software, Slack channels, or custom dashboards.Your endpoint must respond with HTTP 200 within 10 seconds. Failed deliveries follow the platform-wide webhook retry policy documented in API Webhooks; on terminal failure the alert transitions to delivery_failed and escalates per the Guardrails section below. Review delivery logs under Settings > Alerts > Webhook Logs.For full webhook integration documentation, see the Webhooks API reference.

Webhook Payload Example

When an NDVI Drop alert fires, SemaiSens sends a payload structured like this:

{
  "event": "alert.triggered",
  "alert_id": "alr_01j9abc",
  "field_id": "fld_01j8xyz",
  "field_name": "North Corn Field",
  "alert_type": "ndvi_drop",
  "triggered_at": "2024-07-12T08:34:00Z",
  "details": {
    "previous_ndvi": 0.71,
    "current_ndvi": 0.48,
    "drop": 0.23
  }
}

The details object varies by alert type. Threshold alerts include index, threshold_value, and current_value. Weather alerts include weather_event, forecast_value, and forecast_time.

Managing Alerts

Access all alerts across every field from Settings > Alerts in the left sidebar. From this view you can:

Mute an alert for a defined period (e.g., during a planned dormancy period or off-season) without deleting it
Edit thresholds, delivery channels, or conditions at any time
Delete an alert permanently
View history — a log of every time an alert has fired, including delivery status for each channel

Alert notifications are typically delivered within 30 minutes of a new imagery acquisition completing validation and ingestion. Weather alerts fire as soon as the underlying forecast data updates, which occurs every six hours. During periods of high imagery volume across the platform, delivery may occasionally extend to 60 minutes.

Guardrails

This module follows the shared guardrails template. The agent and every non-agent write path must respect these rules. The alert_rule is the human-authored configuration; the alert is the machine-fired instance. Muting acts on the rule, not the instance. Delivery routing acts on the instance.

Category	Rule
Input validation	Rule requires: `field_id[]` or `estate_id`, `alert_type` (`ndvi_drop` \| `threshold` \| `new_imagery` \| `weather`), a valid condition matching the type, and at least one delivery channel. NDVI-drop rules require a `drop_pct` between 5 and 50. Threshold rules require an `index`, `operator`, and `value` in range for the index. Weather rules require a `weather_event` from the supported list and a valid `lead_time_hours`. Webhook endpoints must respond HTTP 200 within 10 seconds on creation test.
Preconditions	Every targeted `field_id` must have an active crop cycle. The actor must have write access to every targeted field or estate. At least one delivery channel must be verified for the actor.
Refusals	Creating a rule targeting a field the actor cannot see (entitlements). Muting a rule that produces severity ≥ high signals beyond the bounded window declared by the safety floor. Deleting a rule that has fired within the last 24 hours without a supervisor confirmation. Setting `mute_until` in the past. Creating a rule with a delivery-only-webhook configuration for Critical or High without an on-call fallback.
Confirmations	Delete a rule with an active firing history (irreversible: future firings stop entirely). Mute a rule whose last firing was Critical or High. Bulk edit across estates. Reversible actions (create, edit conditions, edit channels, mute with a near-term expiry, unmute) commit optimistically with a 5-second undo.
Soft warnings	Rule threshold sits inside the noise band for the target index (informational; user can proceed). Rule targets more than 20 fields in one write. Mute window overlaps a period of historically high firings on the target field. New webhook endpoint has never received a delivery.
Rate and scope limits	Bulk rule creation capped at N per org action (org-configurable) because of notification blast radius. Webhook endpoint creation rate-limited per org. No hard cap on total active rules per user; volume is a soft warning, not a refusal. Alert delivery retries follow the platform webhook retry policy; on terminal failure the `alert` transitions to `delivery_failed` and escalates.
Audit	Every rule write conforms to the Audit Envelope. Module-specific fields: `alert_type`, `conditions_snapshot`, `channels`, `mute_until` (when set), `mute_reason` (when set), `fields_scope[]` or `estate_id`. Every `alert` instance also audits `fired_at`, `matched_rule_id`, `matched_conditions_snapshot`, and per-delivery `channel`, `delivery_outcome`, `receipt_id`. Mutes are audited on the rule (`before_snapshot.mute_until` and `after_snapshot.mute_until`); acknowledgement is audited on the alert instance per user.
Escalation	`delivery_failed` on a Critical or High alert escalates to the estate admin and, if configured, the on-call role. Three failed deliveries on the same rule within 24 hours escalate to the org admin. Attempt to mute a severity ≥ high rule beyond bounds escalates to the estate admin. Rule deletion by a non-admin identity when the rule has fired within 24 hours escalates to the estate admin.

Activity & Alerts - the umbrella module. Covers task, scout, map, imagery, and system activity in addition to field alerts, plus the delivery matrix, digests, and AI escalation.
Risk Model - the rule card schema that defines the thresholds behind every field alert.
Field Scouting - turn alerts into GPS-routed scout tasks.
Notification Preferences - configure channels, quiet hours, and digest cadence.

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Field Alerts: Threshold, Drop, Imagery, and Weather

Field Alert Types

NDVI Drop Alert

Threshold Alert

New Imagery Alert

Weather Alert

Creating an Alert

Delivery Channels

Webhook Payload Example

Managing Alerts

Guardrails

​Field Alert Types

NDVI Drop Alert

Threshold Alert

New Imagery Alert

Weather Alert

​Creating an Alert

​Delivery Channels

​Webhook Payload Example

​Managing Alerts

​Guardrails

​Related

Field Alert Types

Creating an Alert

Delivery Channels

Webhook Payload Example

Managing Alerts

Guardrails

Related