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# NIDLTDOAMeasurement

Information from a Downlink Time-Difference-of-Arrival anchor that you use to derive a range estimate.

```
class NIDLTDOAMeasurement
```

## Overview

Your app runs on a receiver device that fields messages from nearby physical base stations, or *anchors*. The framework processes the messages into instances of this class and provides them to your app through the  [`session(_:didUpdateDLTDOA:)`](/documentation/NearbyInteraction/NISessionDelegate/session(_:didUpdateDLTDOA:)) callback. Your app analyzes the measurements to calculate the receiver’s position relative to the anchors in the tracked area.

Only sessions that run a [`NIDLTDOAConfiguration`](/documentation/NearbyInteraction/NIDLTDOAConfiguration) receive Downlink Time-Difference-of-Arrival measurements.

## Topics

### Identifying the anchor

[`var address: Int`](/documentation/NearbyInteraction/NIDLTDOAMeasurement/address)

A value that uniquely identifies an anchor in a tracked area.

[`var clusterInitiatorAddress: Int`](/documentation/NearbyInteraction/NIDLTDOAMeasurement/clusterInitiatorAddress)

The address of the initiator anchor within the same cluster.

### Locating the anchor

[`var coordinates: simd_double3`](/documentation/NearbyInteraction/NIDLTDOAMeasurement/coordinates)

A triplet that represents the location in 3D space of the anchor that provides the measurement.

[`var coordinatesType: NIDLTDOACoordinatesType`](/documentation/NearbyInteraction/NIDLTDOAMeasurement/coordinatesType)

The type of coordinate system that the measurement conforms to.

[`var signalStrength: Double`](/documentation/NearbyInteraction/NIDLTDOAMeasurement/signalStrength)

A value that represents the received signal strength, in dBm, from the anchor that provides the measurement.

[`var floorElevation: NIDLTDOAMeasurement.FloorElevation?`](/documentation/NearbyInteraction/NIDLTDOAMeasurement/floorElevation-swift.property)

The floor elevation information for the anchor, if available.

[`class FloorElevation`](/documentation/NearbyInteraction/NIDLTDOAMeasurement/FloorElevation-swift.class)

An object that describes how high off the ground DL-TDOA anchors reside in the environment.

### Assessing time difference

[`var receiveTime: Double`](/documentation/NearbyInteraction/NIDLTDOAMeasurement/receiveTime)

A timestamp, in seconds, for the time that the device receives the measurement.

[`var transmitTime: Double`](/documentation/NearbyInteraction/NIDLTDOAMeasurement/transmitTime)

A transmission timestamp, in seconds, for the received message.

### Evaluating the message

[`var measurementType: NIDLTDOAMeasurementType`](/documentation/NearbyInteraction/NIDLTDOAMeasurement/measurementType)

The type of anchor message that the measurement derives from.

[`var carrierFrequencyOffset: Double`](/documentation/NearbyInteraction/NIDLTDOAMeasurement/carrierFrequencyOffset)

The drift, as a ratio, across the frequencies of the receiver and the anchor.

[`var responderClockFrequencyOffset: Double?`](/documentation/NearbyInteraction/NIDLTDOAMeasurement/responderClockFrequencyOffset-8wu5r)

The clock frequency offset of the responder anchor relative to the initiator anchor.

### Creating a measurement

[`init?(coder: NSCoder)`](/documentation/NearbyInteraction/NIDLTDOAMeasurement/init(coder:))

### Instance Properties

[`var rawReceiveTime: UInt64`](/documentation/NearbyInteraction/NIDLTDOAMeasurement/rawReceiveTime)

Indicates the raw reception timestamp (in units of 15.65 picoseconds).

[`var rawTransmitTime: UInt64`](/documentation/NearbyInteraction/NIDLTDOAMeasurement/rawTransmitTime)

Indicates the raw transmission timestamp (in units of 15.65 picoseconds).

## Relationships

### Conforms To

[`NSObjectProtocol`](/documentation/ObjectiveC/NSObjectProtocol)

[`SendableMetatype`](/documentation/Swift/SendableMetatype)

[`CustomDebugStringConvertible`](/documentation/Swift/CustomDebugStringConvertible)

[`NSSecureCoding`](/documentation/Foundation/NSSecureCoding)

[`Hashable`](/documentation/Swift/Hashable)

[`NSCoding`](/documentation/Foundation/NSCoding)

[`Sendable`](/documentation/Swift/Sendable)

[`CVarArg`](/documentation/Swift/CVarArg)

[`CustomStringConvertible`](/documentation/Swift/CustomStringConvertible)

[`Equatable`](/documentation/Swift/Equatable)

[`NSCopying`](/documentation/Foundation/NSCopying)

### Inherits From

[`NSObject-swift.class`](/documentation/ObjectiveC/NSObject-swift.class)

---

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