Global Navigation Satellite System (GNSS) Reference Information Protocol (GRIP) - Global Positioning System (GPS) Assistance Data

This document defines assistance data formats for the Global Positioning System (GPS). These formats can be used with the Global Navigation Satellite System (GNSS) Reference Information Protocol (GRIP) by a GPS receiver to acquire assistance data.

Status of This Memo

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1. Introduction
2. Conventions used in this document
    2.1. Notational Conventions
    2.2. Angular Measures
    2.3. Polynomial Expressions
    2.4. Expressing Reference Time
3. GPS Assistance Data Types
    3.1. UTC Model
    3.2. Navigation Model
        3.2.1. Navigation Model Clock Model
        3.2.2. Navigation Model Orbital Model
        3.2.3. Example Navigation Model
    3.3. Ionosphere Model
    3.4. Acquisition Assistance
    3.5. Differential GPS Corrections
    3.6. Almanac
    3.7. Extended Navigation Model
4. XML Schema
5. Security Considerations
6. IANA Considerations
    6.1. URN Sub-Namespace Registration for 'urn:ietf:params:xml:ns:grip:gps'
    6.2. XML Schema Registration
7. Acknowledgements
8. References
    8.1. Normative References
    8.2. Informative References

1. Introduction

The Global Positioning System (GPS) is a navigation system that provides the means to determine the location of a receiver in space and time with high accuracy. With a large number of satellites, it is the most widely used Global Navigation Satellite System (GNSS).

Server-assisted GPS provides a number of advantages including reducing the time required to measure satellites; reducing the time required to obtain the information necessary to calculate a position; and improving the ability of a receiver to successfully measure satellites in low signal conditions.

2. Conventions used in this document

2.1. Notational Conventions

In naming parameters, the GPS Interface Specification frequently uses mathematical symbols and characters that cannot be represented in this document format. In particular, Greek characters are used to represent many parameters. The following conventions are used in this document to aid in correlating the two texts:

2.2. Angular Measures

The formats described in this document are expressed in units of radians, not semi-circles. When converting, it is important to use the same approximation for the mathematical constant pi as is used by all GPS systems. Using this approximation ensures that the assistance data is generated and applied using the same values.

2.3. Polynomial Expressions

The GPS navigation message is updated infrequently, but it models values that change over time. Thus, the message includes values that model how values change over time.

Many values in GPS assistance data are expressed with a base value that is set at a particularly point in time, plus a value for the rate of change of that value in time. Some values are further expressed with coefficients for the rate of change of the rate of change. In other words, values are expressed as a polynomial function in terms of time.

This extends to other values, such as those in the Ionosphere Model that change depending on longitude. In the GPS navigation message, the Ionosphere model has four polynomial terms, allowing for a more complex model of ionosphere effects across different longitudes.

This document uses a generalized model for univariate polynomial expressions. These expressions are used extensively. Each element that includes a polynomial expression rather than a fixed value includes the definition of the target value (and its units) plus the input variable (and its units).

Polynomial expressions are expressed as simple lists in XML schema, or a space-separated sequence of numbers. The first value in the list is the constant expression; the second value is the first order term; the nth value is the coefficient of the (n-1)th power of the input, giving:

Polynomials can be any length, but since every term needs to be considered when the input variable is anything other than zero, receivers MAY limit their support to as many coefficients as are included in the GPS navigation message. The mandatory number of supported coefficients is included in the definition of polynomials.

2.4. Expressing Reference Time

Where the input variable to a polynomial expression is time, a reference value is commonly used. The input to the polynomial expression is the difference between the current (or applicable) time and the reference time. The value for reference time is usually provided as a separate element in these cases and this element is identified in the definition of the polynomial expression.

The tow element provides a reference time for assistance data that requires a reference. This element includes the GPS time of week in milliseconds to use as a reference. The input variable to time-based polynomials is the difference between the current time and the reference time.

Alternatively, an explicit GPS week number can be indicated in the week attribute of the tow element. Note that GPS week rollovers also occur ever 1024 weeks (approximately 20 years).

3. GPS Assistance Data Types

This section defines assistance data types for GPS. The following definitions are provided:

3.1. UTC Model

The UTC model contains information on the relationship between Coordinated Universal Time (UTC) time and GPS time. The realization of the UTC model used in GPS is the US Naval Observatory realization: UTC(USNO). The UTC model is always global.

The following example shows an instance of the UTC model in XML form, including information on the introduction of a new leap second:

3.2. Navigation Model

The navigation element contains the navigation model, information on the clock and position of each satellite, plus satellite status information. The navigation model is specific to a satellite and forms the bulk of the information transmitted by a satellite.

Navigation model data can be global or local. Global data contains information for all satellites; local data contains on those satellites that can be seen from the input location.

Multiple satellite elements are included in the navigation model, each containing the information for a single satellite. If the information is local, only relevant satellites are included. Each satellite included in the set is identified by number in the number attribute.

Theiod attribute contains the Issue Of Data, Clock (IODC) value from the navigation message. The lower 8 bits of this 10 bit value indicate the Issue of Data, Ephemeris (IODE). This is only included if the information is derived from the navigation message broadcast by the satellite.

Servers MAY choose not to include navigation model information for satellites that have a URA of INF or bad health when providing local assistance data.

The health, l2codes, sf1reserved and aodo elements contain information that might not be relevant to some receivers. These elements are optional, and MUST be omitted if the information provided is not directly taken from the navigation message broadcast by the satellite. This ensures that when present these values can be used by a receiver to compansate for the effect of navigation message modulation on the signal it receives.

3.2.1. Navigation Model Clock Model

The clock element of the satellite navigation model contains information on the clock in the satellite.

3.2.2. Navigation Model Orbital Model

The ephemeris element of the satellite navigation model contains information on the orbit of the satellite.

The fit4hr indicates whether the model is fit over the standard period of 4 hours. If false, the model is based on a longer time frame.

3.2.3. Example Navigation Model

The following example shows an instance of the navigation model in XML form, including a single satellite only:

3.3. Ionosphere Model

The ionosphere contains a model of the signal transmission delays introduced by the Earths ionosphere. Alternative models are available, but this element uses the Klobuchar model that is broadcast in the satellite navigation message. The ionosphere model is always global.

3.4. Acquisition Assistance

The acqAssist element contains an estimate of the measurement a receiver is expected to make at a specified location. Acquisition assistance is always local.

The tow element includes the reference time used in constructing the acquisition assistance.

The following example shows an instance of acquisition assistance in XML form, including a single satellite only:

3.5. Differential GPS Corrections

The dgps element contains an estimate of the pseudorage measurement error. Differential GPS corrections are generated by fixed receivers, which are able to compensate for errors that are not accounted for in other GPS data. Because this information degrades quickly as the distance from the fixed receiver increases, differential GPS corrections are always local.

The tow element includes the reference time used in the differential GPS corrections.

The satellite element for differential corrections has a single range element. This contains a polynomial expression in time for the range correction. At least two coefficients are required. The uncertainty element includes an estimate of the remaining error in this estimate, at 95% confidence.

The following example shows an instance of differential GPS corrections in XML form, including a single satellite only:

3.6. Almanac

The almanac element contains long term information about satelite clock and orbit. Almanac data is always global.

In the navigation message, almanac data is a simplified, low accuracy version of the navigation model. In this XML representation, the data MAY include additional information in the provided fields, providing that the model remains usable over a period equivalent to that of the almanac in the navigation message (182 days).

Almanac is of limited use when a navigation model is available. All satellites transmit this information, so global information is available even where the region covered by the server is not global. Receivers use almanac to provide a rough indication of satellite location after a long period where the receiver does not update other data.

The satellite element contains per-satellite almanac data. The healthy attribute identifies whether the satellite is currently fit for use; a value of false indicates the presence of a problem. The healthy attribute can be omitted if the satellite is healthy.

The following example shows an instance of the almanac in XML form, including a single satellite only:

3.7. Extended Navigation Model

The extended navigation model allows for predictions of ephemeris over a longer period of time than might be allowed for with the basic navigation model. For many parameters, a curve fit using a polynomial with a limited number of coefficients only works for a short time. While data might be sufficiently accurate within the curve fit interval, outside this interval the data becomes increasingly inaccurate.

The extNavigation element includes multiple predictions for satellite clock and ephemeris. These are predictions of future state, based on more elaborate models that the server might maintain. Each prediction has a specific period of time that it is valid for. Thus, a receiver is able to use a new model as the previous model expires.

The extNavigation element contains multiple estimate elements, each of which contains the a complete model, plus an indication of when the model is predicted to be valid.

The validity element includes two GPS time of week (Expressing Reference Time) elements, start and end, that respectively indicate when the estimate becomes valid and when it becomes invalid.

Scheduled events might occur that cause predictions about certain satellites to become invalid. The server MUST omit predictions for affected satellite from the affected period onwards.

The following example shows an instance of extended navigation model data in XML form, including a single estimate and a single satellite only:

4. XML Schema

<xs:schema
    targetNamespace="urn:ietf:params:xml:ns:grip:gps"
    xmlns:xs="http://www.w3.org/2001/XMLSchema"
    xmlns:gps="urn:ietf:params:xml:ns:grip:gps"
    elementFormDefault="qualified"
    attributeFormDefault="unqualified">

  <xs:annotation>
    <xs:appinfo
        source="urn:ietf:params:xml:schema:grip:gps">
      Global Positioning System (GPS) Schema for GRIP
    </xs:appinfo>
    <xs:documentation source="http://www.ietf.org/rfc/rfcXXXX.txt">
<!-- [[NOTE TO RFC-EDITOR: Please replace above URL with URL of
                           published RFC and remove this note.]] -->
      This document defines assistance data for GPS.
    </xs:documentation>
  </xs:annotation>

  <!-- Common types -->
  <xs:element name="tow" type="gps:towType"/>
  <xs:complexType name="towType">
    <xs:simpleContent>
      <xs:extension base="gps:towBaseType">
        <xs:attribute name="week" type="gps:weekType"/>
      </xs:extension>
    </xs:simpleContent>
  </xs:complexType>
  <xs:simpleType name="towBaseType">
    <xs:restriction base="xs:nonNegativeInteger">
      <xs:maxExclusive value="604800000"/> <!-- 7*24*60*60*1000 -->
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="weekType">
    <xs:restriction base="xs:nonNegativeInteger">
      <xs:maxExclusive value="1024"/> <!-- 10 bits -->
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="dayType">
    <xs:restriction base="xs:positiveInteger">
      <xs:maxInclusive value="7"/> <!-- starts at 1 -->
    </xs:restriction>
  </xs:simpleType>

  <xs:simpleType name="nonNegativeDouble">
    <xs:restriction base="xs:double">
      <xs:minInclusive value="0.0"/>
    </xs:restriction>
  </xs:simpleType>

  <xs:simpleType name="polyType">
    <xs:restriction base="gps:polyBaseType">
      <xs:minLength value="1"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="polyBaseType">
    <xs:list itemType="xs:double"/>
  </xs:simpleType>

  <xs:complexType name="polyUncType">
    <xs:simpleContent>
      <xs:extension base="gps:polyType">
        <xs:attribute name="uncertainty"
                      type="gps:nonNegativeDouble"/>
      </xs:extension>
    </xs:simpleContent>
  </xs:complexType>

  <xs:complexType name="perSatelliteBaseType">
    <xs:complexContent>
      <xs:restriction base="xs:anyType">
        <xs:sequence>
          <xs:element name="satellite" type="gps:satelliteBaseType"
                      minOccurs="0" maxOccurs="unbounded"/>
        </xs:sequence>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>
  <xs:complexType name="perSatelliteTowType">
    <xs:complexContent>
      <xs:restriction base="xs:anyType">
        <xs:sequence>
          <xs:element ref="gps:tow"/>
          <xs:element name="satellite" type="gps:satelliteBaseType"
                      minOccurs="0" maxOccurs="unbounded"/>
        </xs:sequence>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>
  <xs:complexType name="satelliteBaseType">
    <xs:complexContent>
      <xs:restriction base="xs:anyType">
        <xs:sequence>
          <xs:any namespace="##any" processContents="strict"
                  minOccurs="1" maxOccurs="unbounded"/>
        </xs:sequence>
        <xs:attribute name="number" type="xs:nonNegativeInteger"
                      use="required"/>
        <xs:anyAttribute namespace="##any" processContents="strict"/>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>

  <!-- UTC -->
  <xs:element name="utc" type="gps:utcType"/>
  <xs:complexType name="utcType">
    <xs:complexContent>
      <xs:restriction base="xs:anyType">
        <xs:sequence>
          <xs:element ref="gps:tow"/>
          <xs:element name="offset" type="gps:polyType"/>
          <xs:element name="leapsec" type="gps:leapsecType"
                      minOccurs="1" maxOccurs="unbounded"/>
        </xs:sequence>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>
  <xs:complexType name="leapsecType">
    <xs:simpleContent>
      <xs:extension base="xs:integer">
        <xs:attribute name="week" type="gps:weekType"/>
        <xs:attribute name="day" type="gps:weekType"/>
      </xs:extension>
    </xs:simpleContent>
  </xs:complexType>

  <!-- Navigation Model -->
  <xs:element name="navigation" type="gps:navigationType"/>
  <xs:complexType name="navigationType">
    <xs:complexContent>
      <xs:restriction base="gps:perSatelliteBaseType">
        <xs:sequence>
          <xs:element name="satellite"
                      type="gps:navigationSatelliteType"
                      minOccurs="0" maxOccurs="unbounded"/>
        </xs:sequence>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>

  <xs:complexType name="navigationSatelliteType">
    <xs:complexContent>
      <xs:restriction base="gps:satelliteBaseType">
        <xs:sequence>
          <xs:element name="ura" type="gps:nonNegativeDouble"/>
          <xs:element name="health" type="gps:healthType"
                      minOccurs="0"/>
          <xs:element name="l2codes" type="gps:l2codesType"
                      minOccurs="0"/>
          <xs:element name="sf1reserved" type="gps:sf1reservedType"
                      minOccurs="0"/>
          <xs:element name="aodo" type="gps:nonNegativeDouble"
                      minOccurs="0"/>
          <xs:element ref="gps:clock"/>
          <xs:element ref="gps:ephemeris"/>
        </xs:sequence>
        <xs:attribute name="iod" type="gps:iodType"/>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>

  <xs:complexType name="healthType">
    <xs:simpleContent>
      <xs:extension base="gps:healthBaseType">
        <xs:attribute name="bad" type="gps:healthBadType"
                      default="none"/>
        <xs:attribute name="signals" type="gps:healthSignalsType"
                      default="all"/>
      </xs:extension>
    </xs:simpleContent>
  </xs:complexType>
  <xs:simpleType name="healthBaseType">
    <xs:restriction base="xs:token">
      <xs:enumeration value="ok"/>
      <xs:enumeration value="weak"/>
      <xs:enumeration value="dead"/>
      <xs:enumeration value="nodata"/>
      <xs:enumeration value="out"/>
      <xs:enumeration value="soonout"/>
      <xs:enumeration value="spare"/>
      <xs:enumeration value="combination"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="healthBadType">
    <xs:restriction base="xs:token">
      <xs:enumeration value="none"/>
      <xs:enumeration value="some"/>
      <xs:enumeration value="parity"/>
      <xs:enumeration value="tlm-how"/>
      <xs:enumeration value="all"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="healthSignalsType">
    <xs:restriction base="xs:token">
      <xs:enumeration value="L1"/>
      <xs:enumeration value="L1P"/>
      <xs:enumeration value="L1C"/>
      <xs:enumeration value="L2"/>
      <xs:enumeration value="L2P"/>
      <xs:enumeration value="L2C"/>
      <xs:enumeration value="all"/>
    </xs:restriction>
  </xs:simpleType>

  <xs:complexType name="l2codesType">
    <xs:simpleContent>
      <xs:extension base="gps:l2codesBaseType">
        <xs:attribute name="pdata" type="xs:boolean" use="required"/>
      </xs:extension>
    </xs:simpleContent>
  </xs:complexType>
  <xs:simpleType name="l2codesBaseType">
    <xs:list>
      <xs:simpleType>
        <xs:restriction base="xs:token">
          <xs:enumeration value="p"/>
          <xs:enumeration value="c/a"/>
        </xs:restriction>
      </xs:simpleType>
    </xs:list>
  </xs:simpleType>

  <xs:simpleType name="sf1reservedType">
    <xs:restriction base="xs:hexBinary">
      <xs:pattern value="[0-7][\da-fA-F]{21}"/> <!-- 87 bits -->
    </xs:restriction>
  </xs:simpleType>

  <xs:element name="clock" type="gps:clockType"/>
  <xs:complexType name="clockType">
    <xs:complexContent>
      <xs:restriction base="xs:anyType">
        <xs:sequence>
          <xs:element ref="gps:tow"/>
          <xs:element name="groupdelay" type="xs:double"/>
          <xs:element name="offset" type="gps:polyType"/>
        </xs:sequence>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>

  <xs:element name="ephemeris" type="gps:ephemerisType"/>
  <xs:complexType name="ephemerisType">
    <xs:complexContent>
      <xs:restriction base="xs:anyType">
        <xs:sequence>
          <xs:element ref="gps:tow"/>
          <xs:group ref="gps:keplerianOrbitBase"/>
          <xs:element name="harmonicCorrection"
                      type="gps:harmonicCorrectionType"/>
        </xs:sequence>
        <xs:attribute name="fit4hr" type="xs:boolean"/>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>

  <xs:group name="keplerianOrbitBase">
    <xs:sequence>
      <xs:element name="semiMajor" type="gps:nonNegativeDouble"/>
      <xs:element name="eccentricity" type="gps:nonNegativeDouble"/>
      <xs:element name="longitude" type="gps:polyType"/>
      <xs:element name="inclination" type="gps:polyType"/>
      <xs:element name="periapsis" type="gps:polyType"/>
      <xs:element name="anomaly" type="gps:polyType"/>
    </xs:sequence>
  </xs:group>

  <xs:complexType name="harmonicCorrectionType">
    <xs:complexContent>
      <xs:restriction base="xs:anyType">
        <xs:sequence>
          <xs:element name="latitude" type="gps:harmonicType"/>
          <xs:element name="radius" type="gps:harmonicType"/>
          <xs:element name="inclination" type="gps:harmonicType"/>
        </xs:sequence>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>
  <xs:simpleType name="harmonicType">
    <xs:restriction base="gps:polyType">
      <xs:length value="2"/> <!-- cosine sine -->
    </xs:restriction>
  </xs:simpleType>

  <xs:simpleType name="iodType">
    <xs:restriction base="xs:nonNegativeInteger">
      <xs:maxExclusive value="1024"/>
    </xs:restriction>
  </xs:simpleType>

  <!-- Almanac -->
  <xs:element name="almanac" type="gps:almanacType"/>
  <xs:complexType name="almanacType">
    <xs:complexContent>
      <xs:restriction base="gps:perSatelliteBaseType">
        <xs:sequence>
          <xs:element name="satellite"
                      type="gps:almanacSatelliteType"
                      minOccurs="0" maxOccurs="unbounded"/>
        </xs:sequence>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>
  <xs:complexType name="almanacSatelliteType">
    <xs:complexContent>
      <xs:restriction base="gps:satelliteBaseType">
        <xs:sequence>
          <xs:element ref="gps:tow"/>
          <xs:element name="clockOffset" type="gps:polyType"/>
          <xs:group ref="gps:keplerianOrbitBase"/>
        </xs:sequence>
        <xs:attribute name="healthy" type="xs:boolean"
                      default="true"/>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>

  <!-- Extended Navigation -->
  <xs:element name="extNavigation" type="gps:extNavigationType"/>
  <xs:complexType name="extNavigationType">
    <xs:complexContent>
      <xs:restriction base="xs:anyType">
        <xs:sequence>
          <xs:element name="estimate" type="gps:estimateType"
                      maxOccurs="unbounded"/>
        </xs:sequence>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>

  <xs:complexType name="estimateType">
    <xs:complexContent>
      <xs:restriction base="xs:anyType">
        <xs:sequence>
          <xs:element name="validity" type="gps:validityType"/>
          <xs:element name="satellite"
                      type="gps:extNavigationSatelliteType"
                      minOccurs="0" maxOccurs="unbounded"/>
        </xs:sequence>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>

  <xs:complexType name="validityType">
    <xs:complexContent>
      <xs:restriction base="xs:anyType">
        <xs:sequence>
          <xs:element name="start" type="gps:towType"/>
          <xs:element name="end" type="gps:towType"/>
        </xs:sequence>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>

  <xs:complexType name="extNavigationSatelliteType">
    <xs:complexContent>
      <xs:restriction base="gps:satelliteBaseType">
        <xs:sequence>
          <xs:element ref="gps:clock"/>
          <xs:element ref="gps:ephemeris"/>
        </xs:sequence>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>

  <!-- Acquisition Assistance -->
  <xs:element name="acqAssist" type="gps:acqAssistType"/>
  <xs:complexType name="acqAssistType">
    <xs:complexContent>
      <xs:restriction base="gps:perSatelliteTowType">
        <xs:sequence>
          <xs:element ref="gps:tow"/>
          <xs:element name="satellite"
                      type="gps:acqAssistSatelliteType"
                      minOccurs="0" maxOccurs="unbounded"/>
        </xs:sequence>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>

  <xs:complexType name="acqAssistSatelliteType">
    <xs:complexContent>
      <xs:restriction base="gps:satelliteBaseType">
        <xs:sequence>
          <xs:element name="rtow" type="gps:towType"/>
          <xs:element name="codephase" type="gps:polyUncType"/>
          <xs:element name="doppler" type="gps:polyUncType"/>
          <xs:element name="direction" type="gps:directionType"/>
        </xs:sequence>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>

  <xs:simpleType name="directionType">
    <xs:restriction base="gps:polyType">
      <xs:maxLength value="2"/>
    </xs:restriction>
  </xs:simpleType>

  <!-- DGPS Corrections -->
  <xs:element name="dgps" type="gps:dgpsType"/>
  <xs:complexType name="dgpsType">
    <xs:complexContent>
      <xs:restriction base="gps:perSatelliteTowType">
        <xs:sequence>
          <xs:element ref="gps:tow"/>
          <xs:element name="satellite" type="gps:dgpsSatelliteType"
                      minOccurs="0" maxOccurs="unbounded"/>
        </xs:sequence>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>

  <xs:complexType name="dgpsSatelliteType">
    <xs:complexContent>
      <xs:restriction base="gps:satelliteBaseType">
        <xs:sequence>
          <xs:element name="range" type="gps:polyUncType"/>
        </xs:sequence>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>

  <!-- Ionosphere Model -->
  <xs:element name="ionosphere" type="gps:ionosphereType"/>
  <xs:complexType name="ionosphereType">
    <xs:complexContent>
      <xs:restriction base="xs:anyType">
        <xs:sequence>
          <xs:element name="vdelay" type="gps:polyType"/>
          <xs:element name="period" type="gps:polyType"/>
        </xs:sequence>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>

</xs:schema>

5. Security Considerations

6. IANA Considerations

6.1. URN Sub-Namespace Registration for 'urn:ietf:params:xml:ns:grip:gps'

6.2. XML Schema Registration

7. Acknowledgements

This document is part of the definition of GRIP. The original GRIP protocol was developed by the University of New South Wales through the OSGRS project http://osgrs.sourceforge.net/. The GPS expertise of Neil Harper was invaluable in assembling this document.

[RFC2119]	Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” BCP 14, RFC 2119, March 1997 (TXT, HTML, XML).
[RFC3688]	Mealling, M., “The IETF XML Registry,” BCP 81, RFC 3688, January 2004 (TXT).
[GPS-IS-200]	GPS Navstar Joint Program Office, “Navstar GPS Space Segment / Navigation User Interfaces,” Interface Specification IS-GPS-200D, December 2004.
[I-D.singh-geopriv-pidf-lo-dynamic]	Schulzrinne, H., Singh, V., Tschofenig, H., and M. Thomson, “Dynamic Extensions to the Presence Information Data Format Location Object (PIDF-LO),” draft-singh-geopriv-pidf-lo-dynamic-09 (work in progress), March 2010 (TXT).

[I-D.thomson-geopriv-grip]	Thomson, M., “Global Position System (GPS) Assistance Data for GRIP,” draft-thomson-geopriv-grip-gps-00 (work in progress), Jul 2009 (TXT).
[W3C.REC-xmlschema-1-20010502]	Beech, D., Thompson, H., Mendelsohn, N., and M. Maloney, “XML Schema Part 1: Structures,” World Wide Web Consortium FirstEdition REC-xmlschema-1-20010502, May 2001 (HTML).

	Martin Thomson
	Andrew Corporation
	PO Box U40
	Wollongong University Campus, NSW 2500
	AU
Phone:	+61 2 4221 2915
EMail:	martin.thomson@andrew.com
URI:	http://www.andrew.com/

Global Navigation Satellite System (GNSS) Reference Information Protocol (GRIP) - Global Positioning System (GPS) Assistance Data
draft-thomson-geopriv-grip-gps-01

Abstract

Status of This Memo

Copyright Notice

Table of Contents

1. Introduction

2. Conventions used in this document

2.1. Notational Conventions

2.2. Angular Measures

2.3. Polynomial Expressions

2.4. Expressing Reference Time

3. GPS Assistance Data Types

3.1. UTC Model

3.2. Navigation Model

3.2.1. Navigation Model Clock Model

3.2.2. Navigation Model Orbital Model

3.2.3. Example Navigation Model

3.3. Ionosphere Model

3.4. Acquisition Assistance

3.5. Differential GPS Corrections

3.6. Almanac

3.7. Extended Navigation Model

4. XML Schema

5. Security Considerations

6. IANA Considerations

6.1. URN Sub-Namespace Registration for 'urn:ietf:params:xml:ns:grip:gps'

6.2. XML Schema Registration

7. Acknowledgements

8. References

8.1. Normative References

8.2. Informative References

Author's Address

Global Navigation Satellite System (GNSS) Reference Information Protocol (GRIP) - Global Positioning System (GPS) Assistance Datadraft-thomson-geopriv-grip-gps-01

Abstract

Status of This Memo

Copyright Notice

Table of Contents

1. Introduction

2. Conventions used in this document

2.1. Notational Conventions

2.2. Angular Measures

2.3. Polynomial Expressions

2.4. Expressing Reference Time

3. GPS Assistance Data Types

3.1. UTC Model

3.2. Navigation Model

3.2.1. Navigation Model Clock Model

3.2.2. Navigation Model Orbital Model

3.2.3. Example Navigation Model

3.3. Ionosphere Model

3.4. Acquisition Assistance

3.5. Differential GPS Corrections

3.6. Almanac

3.7. Extended Navigation Model

4. XML Schema

5. Security Considerations

6. IANA Considerations

6.1. URN Sub-Namespace Registration for 'urn:ietf:params:xml:ns:grip:gps'

6.2. XML Schema Registration

7. Acknowledgements

8. References

8.1. Normative References

8.2. Informative References

Author's Address

Global Navigation Satellite System (GNSS) Reference Information Protocol (GRIP) - Global Positioning System (GPS) Assistance Data
draft-thomson-geopriv-grip-gps-01