Glossary > Presence Information Data Format Location Object (PIDF-LO)

Presence Information Data Format Location Object (PIDF-LO)

Author: Anagha Ravi

Published: June 24, 2025

Updated: June 25, 2025

What is PIDF-LO?

PIDF-LO stands for Presence Information Data Format Location Object (PIDF-LO). It’s a flexible method to represent location information in a Session Initiation Protocol (SIP) header with XML schema.

When an E911 call is placed, PIDF-LO takes location data and sends them natively across the internet. This leads to instant, accurate location provisioning as a caller moves around a campus or high-rise environment.

PIDF-LO FAQs

What are the benefits of PIDF-LO?

By using a 911 routing technology built on PIDF-LO, businesses can send up-to-the-minute, accurate location information to the correct PSAP during emergency situations.

This is an ideal emergency solution, particularly for campus, high-rise, or highly mobile workers, as PIDF-LO will dynamically check for location information under various scenarios rather than a one-time static location of a traditional provisioning process.

Bandwidth’s 911 Dynamic Location Routing is built on PIDF-LO technology, providing 911 call takers with extremely accurate location information even before the call is answered. This allows emergency call takers to send help to where you are located, versus what city/state your phone may be registered in.

What methods are available for transmitting PIDF-LO?

PIDF-LO data can be transmitted using several methods, each with its own advantages and considerations. The choice of method often depends on the specific application, network infrastructure, and desired level of real-time responsiveness. Here’s a breakdown of the most common approaches:

1. SIP Header Insertion (PIDF-LO SIP Header)

This is the most prevalent method. As the keyword ‘PIDF-LO sip header’ suggests, PIDF-LO data is embedded directly within the SIP (Session Initiation Protocol) headers of signaling messages. This allows the location information to travel alongside the call setup and control signaling, providing a relatively seamless integration. Details on implementing this technique can be found in RFC 6442.

How it works: The PIDF-LO data is formatted and encoded (typically using XML or JSON) and then placed within a designated SIP header field, such as the Geolocation header or a custom header.
Advantages: Minimal overhead, real-time delivery (as it travels with SIP signaling), widely supported by SIP infrastructure.
Considerations: Header size limitations can be a factor with large PIDF-LO payloads. Proper encoding is crucial for compatibility and the use of TCP is recommended over UDP to avoid packet fragmentation.

2. HTTP POST

PIDF-LO data can also be transmitted via HTTP POST requests (commonly referred to as HELD as in RFC 5985). This method is often used when SIP signaling isn’t directly involved or when a more robust data transfer mechanism is preferred.

How it works: A server initiates an HTTP POST request to a designated endpoint, including the PIDF-LO data in the request body.
Advantages: Suitable for non-SIP environments, can handle larger payloads than SIP headers, allows for more complex data structures.
Considerations: Introduces latency compared to SIP header insertion, requires a dedicated HTTP server and endpoint.

3. WebSocket

WebSockets provide a persistent, bidirectional communication channel between a client and a server. This makes them suitable for transmitting PIDF-LO data in near real-time.

How it works: A WebSocket connection is established, and PIDF-LO data is sent as messages over the connection.
Advantages: Low latency, bidirectional communication, suitable for applications requiring frequent updates.
Considerations: Requires WebSocket support on both client and server, can be more resource-intensive than other methods.

4. Custom Signaling Protocols

In some cases, organizations may develop custom signaling protocols to transport PIDF-LO data. This approach offers the greatest flexibility but also requires significant development effort.

How it works: A proprietary protocol is designed to carry PIDF-LO data alongside other signaling information.
Advantages: Maximum control over data format and transmission behavior.
Considerations: High development cost, limited interoperability.

How does PIDF-LO handle different types of location representations?

One of the key strengths of PIDF-LO (Presence Information Data Format Location Object) is its flexibility in accommodating various ways to describe a location. It recognizes that “location” can mean different things depending on the context and the source of the information. PIDF-LO achieves this by using a structured format, typically based on XML and the Geodetic and Geographic Location Markup Language (GML), allowing for multiple types of location data within a single location object.

Here are the primary ways PIDF-LO represents location:

1. Geographic coordinates (Geodetic location)

This is the most common machine-readable representation. It specifies a precise point on the Earth’s surface using coordinates like latitude, longitude, and potentially altitude. PIDF-LO uses GML elements to define points, lines, or even polygons to represent a location or an area.

Example: A GPS reading providing a specific latitude and longitude.
Use Case: Ideal for mapping applications, tracking, and routing where precise point data is needed.

2. Civic address

This represents a location using human-readable information like street name, house number, city, state, postal code, and country. While geographic coordinates are precise for machines, civic addresses are essential for human understanding and interaction, particularly for services like emergency response (E911).

Example: “123 Main St, Anytown, CA 90210, USA.”
Use Case: Absolutely critical for routing emergency calls to the correct Public Safety Answering Point (PSAP) and dispatching first responders. Bandwidth’s experience in E911 highlights the importance of accurate and validated civic addresses transmitted via PIDF-LO.

3. Geographic shapes and areas

Sometimes, a device’s precise location isn’t known, or it’s more useful to indicate an area. PIDF-LO can represent locations as shapes like circles, ellipses, or polygons. This is useful when the location source provides a less precise fix or when describing a zone rather than a single point.

Example: “Within 50 meters of the intersection of Elm St and Oak Ave.”
Use Case: Estimating location based on cell tower triangulation or Wi-Fi positioning where the exact point is uncertain.

4. How PIDF-LO combines representations

The structure of a PIDF-LO document allows it to include multiple location representations simultaneously. For instance, a single PIDF-LO object can contain both the precise geographic coordinates from a device’s GPS and a civic address derived from that coordinate or provided separately. This redundancy and ability to combine different types of location data enhance reliability and usability for various applications.

By supporting these diverse formats, PIDF-LO ensures that location information can be transmitted effectively, regardless of how it was obtained or how it needs to be used by the receiving system.

How does the PIDF-LO SIP header work?

PIDF-LO data is commonly transmitted within SIP (Session Initiation Protocol) messages to carry location alongside real-time communication signals. This is achieved primarily through the use of a designated Location SIP header.

Within this `Location` header, the PIDF-LO XML document is embedded, typically encoded using a content type like application/pidf+xml. This encoding tells the receiving SIP endpoint exactly what kind of data is included.

When a device initiates a SIP call or message, it can include this header containing its location (e.g., GPS coordinates or civic address). The receiving system can then extract and utilize this information.

For Bandwidth, this integration is vital, especially for Emergency Calling services like VoIP E911. By carrying the accurate location data within the SIP header, we ensure that emergency calls can be quickly and reliably routed to the correct Public Safety Answering Point (PSAP), leveraging the efficiency of the SIP protocol itself. It’s a streamlined way to make critical location information available precisely when needed during a communication session.

What are the use cases of PIDF-LO?

PIDF-LO (Presence Information Data Format Location Object) isn’t just a technical specification; it’s a powerful tool enabling a wide range of applications. It’s a key technology in enhancing the accuracy and efficiency of emergency services, particularly in situations where precise location data is crucial. Essentially, it’s about leveraging location data within real-time communication.

The most critical use case is E911 Compliance. This is paramount for VoIP providers like Bandwidth. PIDF-LO allows us to accurately report a caller’s location to emergency services, ensuring rapid response in critical situations. This helps with:

Improved emergency response in urban areas

In densely populated urban environments, the traditional method of determining a caller’s location based on cell tower triangulation can be inaccurate, often leading to delays or misdirection. PIDF-LO addresses this issue by providing 911 call takers with the exact GPS coordinates of a caller, even if they are inside a building or in an area with a poor cellular signal. This allows responders to bypass the uncertainty of triangulation and head straight to the caller’s location, potentially saving precious minutes in a life-threatening situation.

Enhanced location accuracy for nomadic and mobile devices

PIDF-LO is particularly useful for soft phones on tablets or mobile phones, where location information is frequently needed in emergencies. Whether you’re calling 911 from a vehicle, on foot, or in an area with poor infrastructure, PIDF-LO ensures that emergency services are not dependent on less reliable location tracking methods, such as cell tower proximity or Wi-Fi hotspots. This level of accuracy is especially beneficial when every second counts, such as in medical emergencies or accidents that occur outside of urban areas.

Aid for emergency situations in remote or rural areas

In remote or rural areas, where cell tower coverage is sparse or inconsistent, accurate location data can differentiate between a swift rescue and a prolonged delay. PIDF-LO ensures that even in these hard-to-reach locations, emergency call centers receive precise location data, which allows first responders to navigate challenging terrains and reach individuals more efficiently. This is particularly vital for incidents such as hiking accidents or natural disasters, where the caller cannot provide their location verbally.

Beyond emergency services, PIDF-LO unlocks several other valuable applications:

Presence Information: Displaying a user’s location on a presence list (“Available – at [location]”) enhances communication and collaboration.
Location-Based Services: Businesses can tailor services based on a user’s location, such as providing localized content or offers.
Fleet Management: Tracking the location of vehicles or personnel in real-time.
Geo-Fencing: Triggering actions based on a device entering or leaving a defined geographic area.
Enhanced Call Routing: Routing calls based on a user’s location, optimizing network performance and reducing latency.

Ensure faster emergency response with Dynamic Location Routing

In an emergency, every second counts. Bandwidth’s VOIP E911 Dynamic Location Routing, powered by PIDF-LO technology, provides emergency call takers with highly accurate location information even before the call is answered. This allows them to send help directly to your precise location, no matter where you are, rather than relying on the city or state where your phone is registered.

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The information provided in this glossary definition does not, and is not intended to, constitute legal advice, nor does it necessarily represent Bandwidth's products or business practices. This page is for general informational purposes only.

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