draft-ietf-geopriv-uncertainty-01.txt | draft-ietf-geopriv-uncertainty-02.txt | |||
---|---|---|---|---|

GEOPRIV M. Thomson | GEOPRIV M. Thomson | |||

Internet-Draft Mozilla | Internet-Draft Mozilla | |||

Intended status: Standards Track J. Winterbottom | Intended status: Standards Track J. Winterbottom | |||

Expires: January 5, 2015 Unaffiliated | Expires: February 15, 2015 Unaffiliated | |||

July 4, 2014 | August 14, 2014 | |||

Representation of Uncertainty and Confidence in PIDF-LO | Representation of Uncertainty and Confidence in PIDF-LO | |||

draft-ietf-geopriv-uncertainty-01 | draft-ietf-geopriv-uncertainty-02 | |||

Abstract | Abstract | |||

The key concepts of uncertainty and confidence as they pertain to | The key concepts of uncertainty and confidence as they pertain to | |||

location information are defined. Methods for the manipulation of | location information are defined. Methods for the manipulation of | |||

location estimates that include uncertainty information are outlined. | location estimates that include uncertainty information are outlined. | |||

Status of This Memo | Status of This Memo | |||

This Internet-Draft is submitted in full conformance with the | This Internet-Draft is submitted in full conformance with the | |||

skipping to change at page 1, line 33 | skipping to change at page 1, line 33 | |||

Internet-Drafts are working documents of the Internet Engineering | Internet-Drafts are working documents of the Internet Engineering | |||

Task Force (IETF). Note that other groups may also distribute | Task Force (IETF). Note that other groups may also distribute | |||

working documents as Internet-Drafts. The list of current Internet- | working documents as Internet-Drafts. The list of current Internet- | |||

Drafts is at http://datatracker.ietf.org/drafts/current/. | Drafts is at http://datatracker.ietf.org/drafts/current/. | |||

Internet-Drafts are draft documents valid for a maximum of six months | Internet-Drafts are draft documents valid for a maximum of six months | |||

and may be updated, replaced, or obsoleted by other documents at any | and may be updated, replaced, or obsoleted by other documents at any | |||

time. It is inappropriate to use Internet-Drafts as reference | time. It is inappropriate to use Internet-Drafts as reference | |||

material or to cite them other than as "work in progress." | material or to cite them other than as "work in progress." | |||

This Internet-Draft will expire on January 5, 2015. | This Internet-Draft will expire on February 15, 2015. | |||

Copyright Notice | Copyright Notice | |||

Copyright (c) 2014 IETF Trust and the persons identified as the | Copyright (c) 2014 IETF Trust and the persons identified as the | |||

document authors. All rights reserved. | document authors. All rights reserved. | |||

This document is subject to BCP 78 and the IETF Trust's Legal | This document is subject to BCP 78 and the IETF Trust's Legal | |||

Provisions Relating to IETF Documents | Provisions Relating to IETF Documents | |||

(http://trustee.ietf.org/license-info) in effect on the date of | (http://trustee.ietf.org/license-info) in effect on the date of | |||

publication of this document. Please review these documents | publication of this document. Please review these documents | |||

skipping to change at page 2, line 32 | skipping to change at page 2, line 32 | |||

5. Manipulation of Uncertainty . . . . . . . . . . . . . . . . . 13 | 5. Manipulation of Uncertainty . . . . . . . . . . . . . . . . . 13 | |||

5.1. Reduction of a Location Estimate to a Point . . . . . . . 13 | 5.1. Reduction of a Location Estimate to a Point . . . . . . . 13 | |||

5.1.1. Centroid Calculation . . . . . . . . . . . . . . . . 14 | 5.1.1. Centroid Calculation . . . . . . . . . . . . . . . . 14 | |||

5.1.1.1. Arc-Band Centroid . . . . . . . . . . . . . . . . 14 | 5.1.1.1. Arc-Band Centroid . . . . . . . . . . . . . . . . 14 | |||

5.1.1.2. Polygon Centroid . . . . . . . . . . . . . . . . 15 | 5.1.1.2. Polygon Centroid . . . . . . . . . . . . . . . . 15 | |||

5.2. Conversion to Circle or Sphere . . . . . . . . . . . . . 17 | 5.2. Conversion to Circle or Sphere . . . . . . . . . . . . . 17 | |||

5.3. Three-Dimensional to Two-Dimensional Conversion . . . . . 18 | 5.3. Three-Dimensional to Two-Dimensional Conversion . . . . . 18 | |||

5.4. Increasing and Decreasing Uncertainty and Confidence . . 19 | 5.4. Increasing and Decreasing Uncertainty and Confidence . . 19 | |||

5.4.1. Rectangular Distributions . . . . . . . . . . . . . . 19 | 5.4.1. Rectangular Distributions . . . . . . . . . . . . . . 19 | |||

5.4.2. Normal Distributions . . . . . . . . . . . . . . . . 20 | 5.4.2. Normal Distributions . . . . . . . . . . . . . . . . 20 | |||

5.5. Determining Whether a Location is Within a Given Region . 21 | 5.5. Determining Whether a Location is Within a Given Region . 20 | |||

5.5.1. Determining the Area of Overlap for Two Circles . . . 22 | 5.5.1. Determining the Area of Overlap for Two Circles . . . 22 | |||

5.5.2. Determining the Area of Overlap for Two Polygons . . 23 | 5.5.2. Determining the Area of Overlap for Two Polygons . . 23 | |||

6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 23 | 6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 23 | |||

6.1. Reduction to a Point or Circle . . . . . . . . . . . . . 23 | 6.1. Reduction to a Point or Circle . . . . . . . . . . . . . 23 | |||

6.2. Increasing and Decreasing Confidence . . . . . . . . . . 27 | 6.2. Increasing and Decreasing Confidence . . . . . . . . . . 27 | |||

6.3. Matching Location Estimates to Regions of Interest . . . 27 | 6.3. Matching Location Estimates to Regions of Interest . . . 27 | |||

6.4. PIDF-LO With Confidence Example . . . . . . . . . . . . . 28 | 6.4. PIDF-LO With Confidence Example . . . . . . . . . . . . . 28 | |||

7. Confidence Schema . . . . . . . . . . . . . . . . . . . . . . 28 | 7. Confidence Schema . . . . . . . . . . . . . . . . . . . . . . 28 | |||

8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30 | 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30 | |||

8.1. URN Sub-Namespace Registration for | 8.1. URN Sub-Namespace Registration for | |||

urn:ietf:params:xml:ns:geopriv:conf . . . . . . . . . . . 30 | urn:ietf:params:xml:ns:geopriv:conf . . . . . . . . . . . 30 | |||

8.2. XML Schema Registration . . . . . . . . . . . . . . . . . 30 | 8.2. XML Schema Registration . . . . . . . . . . . . . . . . . 30 | |||

9. Security Considerations . . . . . . . . . . . . . . . . . . . 31 | 9. Security Considerations . . . . . . . . . . . . . . . . . . . 31 | |||

10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 31 | 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 31 | |||

11. References . . . . . . . . . . . . . . . . . . . . . . . . . 31 | 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 31 | |||

11.1. Normative References . . . . . . . . . . . . . . . . . . 31 | 11.1. Normative References . . . . . . . . . . . . . . . . . . 31 | |||

11.2. Informative References . . . . . . . . . . . . . . . . . 31 | 11.2. Informative References . . . . . . . . . . . . . . . . . 32 | |||

Appendix A. Conversion Between Cartesian and Geodetic | Appendix A. Conversion Between Cartesian and Geodetic | |||

Coordinates in WGS84 . . . . . . . . . . . . . . . . 33 | Coordinates in WGS84 . . . . . . . . . . . . . . . . 33 | |||

Appendix B. Calculating the Upward Normal of a Polygon . . . . . 34 | Appendix B. Calculating the Upward Normal of a Polygon . . . . . 34 | |||

B.1. Checking that a Polygon Upward Normal Points Up . . . . . 35 | B.1. Checking that a Polygon Upward Normal Points Up . . . . . 35 | |||

Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 35 | Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 35 | |||

1. Introduction | 1. Introduction | |||

Location information represents an estimation of the position of a | Location information represents an estimation of the position of a | |||

Target [RFC6280]. Under ideal circumstances, a location estimate | Target [RFC6280]. Under ideal circumstances, a location estimate | |||

skipping to change at page 4, line 13 | skipping to change at page 4, line 13 | |||

mathematics, particularly statistics and geometry. | mathematics, particularly statistics and geometry. | |||

Some terminology is borrowed from [RFC3693] and [RFC6280], in | Some terminology is borrowed from [RFC3693] and [RFC6280], in | |||

particular Target. | particular Target. | |||

Mathematical formulae are presented using the following notation: add | Mathematical formulae are presented using the following notation: add | |||

"+", subtract "-", multiply "*", divide "/", power "^" and absolute | "+", subtract "-", multiply "*", divide "/", power "^" and absolute | |||

value "|x|". Precedence is indicated using parentheses. | value "|x|". Precedence is indicated using parentheses. | |||

Mathematical functions are represented by common abbreviations: | Mathematical functions are represented by common abbreviations: | |||

square root "sqrt(x)", sine "sin(x)", cosine "cos(x)", inverse cosine | square root "sqrt(x)", sine "sin(x)", cosine "cos(x)", inverse cosine | |||

"acos(x)", tangent "tan(x)", inverse tangent "atan(x)", error | "acos(x)", tangent "tan(x)", inverse tangent "atan(x)", two-argument | |||

function "erf(x)", and inverse error function "erfinv(x)". | inverse tangent "atan2(y,x)", error function "erf(x)", and inverse | |||

error function "erfinv(x)". | ||||

2. A General Definition of Uncertainty | 2. A General Definition of Uncertainty | |||

Uncertainty results from the limitations of measurement. In | Uncertainty results from the limitations of measurement. In | |||

measuring any observable quantity, errors from a range of sources | measuring any observable quantity, errors from a range of sources | |||

affect the result. Uncertainty is a quantification of what is known | affect the result. Uncertainty is a quantification of what is known | |||

about the observed quantity, either through the limitations of | about the observed quantity, either through the limitations of | |||

measurement or through inherent variability of the quantity. | measurement or through inherent variability of the quantity. | |||

Uncertainty is most completely described by a probability | Uncertainty is most completely described by a probability | |||

skipping to change at page 19, line 25 | skipping to change at page 19, line 25 | |||

extrapolated. In particular, the uncertainty can be scaled to meet a | extrapolated. In particular, the uncertainty can be scaled to meet a | |||

desired confidence or the confidence for a particular region of | desired confidence or the confidence for a particular region of | |||

uncertainty can be found. | uncertainty can be found. | |||

In general, confidence decreases as the region of uncertainty | In general, confidence decreases as the region of uncertainty | |||

decreases in size and confidence increases as the region of | decreases in size and confidence increases as the region of | |||

uncertainty increases in size. However, this depends on the PDF; | uncertainty increases in size. However, this depends on the PDF; | |||

expanding the region of uncertainty for a rectangular distribution | expanding the region of uncertainty for a rectangular distribution | |||

has no effect on confidence without additional information. If the | has no effect on confidence without additional information. If the | |||

region of uncertainty is increased during the process of obfuscation | region of uncertainty is increased during the process of obfuscation | |||

(see [I-D.thomson-geopriv-location-obscuring]), then the confidence | (see [RFC6772]), then the confidence cannot be increased. | |||

cannot be increased. | ||||

A region of uncertainty that is reduced in size always has a lower | A region of uncertainty that is reduced in size always has a lower | |||

confidence. | confidence. | |||

A region of uncertainty that has an unknown PDF shape cannot be | A region of uncertainty that has an unknown PDF shape cannot be | |||

reduced in size reliably. The region of uncertainty can be expanded, | reduced in size reliably. The region of uncertainty can be expanded, | |||

but only if confidence is not increased. | but only if confidence is not increased. | |||

This section makes the simplifying assumption that location | This section makes the simplifying assumption that location | |||

information is symmetrically and evenly distributed in each | information is symmetrically and evenly distributed in each | |||

skipping to change at page 29, line 26 | skipping to change at page 29, line 19 | |||

</xs:appinfo> | </xs:appinfo> | |||

<xs:documentation source="http://www.ietf.org/rfc/rfcXXXX.txt"> | <xs:documentation source="http://www.ietf.org/rfc/rfcXXXX.txt"> | |||

<!-- [[NOTE TO RFC-EDITOR: Please replace above URL with URL of | <!-- [[NOTE TO RFC-EDITOR: Please replace above URL with URL of | |||

published RFC and remove this note.]] --> | published RFC and remove this note.]] --> | |||

This schema defines an element that is used for indicating | This schema defines an element that is used for indicating | |||

confidence in PIDF-LO documents. | confidence in PIDF-LO documents. | |||

</xs:documentation> | </xs:documentation> | |||

</xs:annotation> | </xs:annotation> | |||

<xs:element name="confidence" type="conf:confidenceType"/> | <xs:element name="confidence" type="conf:confidenceType"/> | |||

<xs:complexType name="confidenceType"> | <xs:complexType name="confidenceType"> | |||

<xs:simpleContent> | <xs:simpleContent> | |||

<xs:extension base="conf:confidenceBase"> | <xs:extension base="conf:confidenceBase"> | |||

<xs:attribute name="pdf" type="conf:pdfType" | <xs:attribute name="pdf" type="conf:pdfType" | |||

default="unknown"/> | default="unknown"/> | |||

</xs:extension> | </xs:extension> | |||

</xs:simpleContent> | </xs:simpleContent> | |||

</xs:complexType> | </xs:complexType> | |||

<xs:simpleType name="confidenceBase"> | <xs:simpleType name="confidenceBase"> | |||

<xs:union> | <xs:union> | |||

<xs:restriction base="xs:decimal"> | <xs:simpleType> | |||

<xs:minInclusive value="0.0"/> | <xs:restriction base="xs:decimal"> | |||

<xs:maxInclusive value="100.0"/> | <xs:minExclusive value="0.0"/> | |||

</xs:restriction> | <xs:maxExclusive value="100.0"/> | |||

<xs:restriction base="xs:token"> | </xs:restriction> | |||

<xs:enumeration value="unknown"/> | </xs:simpleType> | |||

</xs:restriction> | <xs:simpleType> | |||

<xs:restriction base="xs:token"> | ||||

<xs:enumeration value="unknown"/> | ||||

</xs:restriction> | ||||

</xs:simpleType> | ||||

</xs:union> | ||||

</xs:simpleType> | </xs:simpleType> | |||

<xs:simpleType name="pdfType"> | <xs:simpleType name="pdfType"> | |||

<xs:restriction base="xs:token"> | <xs:restriction base="xs:token"> | |||

<xs:enumeration value="unknown"/> | <xs:enumeration value="unknown"/> | |||

<xs:enumeration value="normal"/> | <xs:enumeration value="normal"/> | |||

<xs:enumeration value="rectangular"/> | <xs:enumeration value="rectangular"/> | |||

</xs:restriction> | </xs:restriction> | |||

</xs:simpleType> | </xs:simpleType> | |||

</xs:schema> | </xs:schema> | |||

8. IANA Considerations | 8. IANA Considerations | |||

8.1. URN Sub-Namespace Registration for | 8.1. URN Sub-Namespace Registration for | |||

urn:ietf:params:xml:ns:geopriv:conf | urn:ietf:params:xml:ns:geopriv:conf | |||

This section registers a new XML namespace, | This section registers a new XML namespace, | |||

"urn:ietf:params:xml:ns:geopriv:conf", as per the guidelines in | "urn:ietf:params:xml:ns:geopriv:conf", as per the guidelines in | |||

[RFC3688]. | [RFC3688]. | |||

skipping to change at page 31, line 34 | skipping to change at page 31, line 34 | |||

11. References | 11. References | |||

11.1. Normative References | 11.1. Normative References | |||

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate | [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate | |||

Requirement Levels", BCP 14, RFC 2119, March 1997. | Requirement Levels", BCP 14, RFC 2119, March 1997. | |||

[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, | [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, | |||

January 2004. | January 2004. | |||

[RFC3693] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and | ||||

J. Polk, "Geopriv Requirements", RFC 3693, February 2004. | ||||

[RFC4119] Peterson, J., "A Presence-based GEOPRIV Location Object | [RFC4119] Peterson, J., "A Presence-based GEOPRIV Location Object | |||

Format", RFC 4119, December 2005. | Format", RFC 4119, December 2005. | |||

[RFC5139] Thomson, M. and J. Winterbottom, "Revised Civic Location | ||||

Format for Presence Information Data Format Location | ||||

Object (PIDF-LO)", RFC 5139, February 2008. | ||||

[RFC5491] Winterbottom, J., Thomson, M., and H. Tschofenig, "GEOPRIV | ||||

Presence Information Data Format Location Object (PIDF-LO) | ||||

Usage Clarification, Considerations, and Recommendations", | ||||

RFC 5491, March 2009. | ||||

[RFC6225] Polk, J., Linsner, M., Thomson, M., and B. Aboba, "Dynamic | ||||

Host Configuration Protocol Options for Coordinate-Based | ||||

Location Configuration Information", RFC 6225, July 2011. | ||||

[RFC6280] Barnes, R., Lepinski, M., Cooper, A., Morris, J., | ||||

Tschofenig, H., and H. Schulzrinne, "An Architecture for | ||||

Location and Location Privacy in Internet Applications", | ||||

BCP 160, RFC 6280, July 2011. | ||||

11.2. Informative References | 11.2. Informative References | |||

[Convert] Burtch, R., "A Comparison of Methods Used in Rectangular | [Convert] Burtch, R., "A Comparison of Methods Used in Rectangular | |||

to Geodetic Coordinate Transformations", April 2006. | to Geodetic Coordinate Transformations", April 2006. | |||

[GeoShape] | [GeoShape] | |||

Thomson, M. and C. Reed, "GML 3.1.1 PIDF-LO Shape | Thomson, M. and C. Reed, "GML 3.1.1 PIDF-LO Shape | |||

Application Schema for use by the Internet Engineering | Application Schema for use by the Internet Engineering | |||

Task Force (IETF)", Candidate OpenGIS Implementation | Task Force (IETF)", Candidate OpenGIS Implementation | |||

Specification 06-142r1, Version: 1.0, April 2007. | Specification 06-142r1, Version: 1.0, April 2007. | |||

[I-D.thomson-geopriv-location-obscuring] | ||||

Thomson, M., "Obscuring Location", draft-thomson-geopriv- | ||||

location-obscuring-03 (work in progress), June 2011. | ||||

[ISO.GUM] ISO/IEC, "Guide to the expression of uncertainty in | [ISO.GUM] ISO/IEC, "Guide to the expression of uncertainty in | |||

measurement (GUM)", Guide 98:1995, 1995. | measurement (GUM)", Guide 98:1995, 1995. | |||

[NIST.TN1297] | [NIST.TN1297] | |||

Taylor, B. and C. Kuyatt, "Guidelines for Evaluating and | Taylor, B. and C. Kuyatt, "Guidelines for Evaluating and | |||

Expressing the Uncertainty of NIST Measurement Results", | Expressing the Uncertainty of NIST Measurement Results", | |||

Technical Note 1297, Sep 1994. | Technical Note 1297, Sep 1994. | |||

[RFC3693] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and | ||||

J. Polk, "Geopriv Requirements", RFC 3693, February 2004. | ||||

[RFC5139] Thomson, M. and J. Winterbottom, "Revised Civic Location | ||||

Format for Presence Information Data Format Location | ||||

Object (PIDF-LO)", RFC 5139, February 2008. | ||||

[RFC5222] Hardie, T., Newton, A., Schulzrinne, H., and H. | [RFC5222] Hardie, T., Newton, A., Schulzrinne, H., and H. | |||

Tschofenig, "LoST: A Location-to-Service Translation | Tschofenig, "LoST: A Location-to-Service Translation | |||

Protocol", RFC 5222, August 2008. | Protocol", RFC 5222, August 2008. | |||

[RFC5491] Winterbottom, J., Thomson, M., and H. Tschofenig, "GEOPRIV | [RFC6772] Schulzrinne, H., Tschofenig, H., Cuellar, J., Polk, J., | |||

Presence Information Data Format Location Object (PIDF-LO) | Morris, J., and M. Thomson, "Geolocation Policy: A | |||

Usage Clarification, Considerations, and Recommendations", | Document Format for Expressing Privacy Preferences for | |||

RFC 5491, March 2009. | Location Information", RFC 6772, January 2013. | |||

[RFC6225] Polk, J., Linsner, M., Thomson, M., and B. Aboba, "Dynamic | ||||

Host Configuration Protocol Options for Coordinate-Based | ||||

Location Configuration Information", RFC 6225, July 2011. | ||||

[RFC6280] Barnes, R., Lepinski, M., Cooper, A., Morris, J., | ||||

Tschofenig, H., and H. Schulzrinne, "An Architecture for | ||||

Location and Location Privacy in Internet Applications", | ||||

BCP 160, RFC 6280, July 2011. | ||||

[Sunday02] | [Sunday02] | |||

Sunday, D., "Fast polygon area and Newell normal | Sunday, D., "Fast polygon area and Newell normal | |||

computation", Journal of Graphics Tools JGT, | computation", Journal of Graphics Tools JGT, | |||

7(2):9-13,2002, 2002, | 7(2):9-13,2002, 2002, | |||

<http://www.acm.org/jgt/papers/Sunday02/>. | <http://www.acm.org/jgt/papers/Sunday02/>. | |||

[TS-3GPP-23_032] | [TS-3GPP-23_032] | |||

3GPP, "Universal Geographic Area Description (GAD)", 3GPP | 3GPP, "Universal Geographic Area Description (GAD)", 3GPP | |||

TS 23.032 11.0.0, September 2012. | TS 23.032 11.0.0, September 2012. | |||

skipping to change at page 34, line 4 | skipping to change at page 34, line 4 | |||

error, is described by the following: | error, is described by the following: | |||

p = sqrt(X^2 + Y^2) | p = sqrt(X^2 + Y^2) | |||

r = sqrt(X^2 + Y^2 + Z^2) | r = sqrt(X^2 + Y^2 + Z^2) | |||

u = atan((1-f) * Z * (1 + e'^2 * (1-f) * R / r) / p) | u = atan((1-f) * Z * (1 + e'^2 * (1-f) * R / r) / p) | |||

latitude = atan((Z + e'^2 * (1-f) * R * sin(u)^3) | latitude = atan((Z + e'^2 * (1-f) * R * sin(u)^3) | |||

/ (p - e^2 * R * cos(u)^3)) | / (p - e^2 * R * cos(u)^3)) | |||

longitude = atan(Y / X) | longitude = atan2(Y, X) | |||

altitude = sqrt((p - R * cos(u))^2 + (Z - (1-f) * R * sin(u))^2) | altitude = sqrt((p - R * cos(u))^2 + (Z - (1-f) * R * sin(u))^2) | |||

If the point is near the poles, that is "p < 1", the value for | If the point is near the poles, that is "p < 1", the value for | |||

altitude that this method produces is unstable. A simpler method for | altitude that this method produces is unstable. A simpler method for | |||

determining the altitude of a point near the poles is: | determining the altitude of a point near the poles is: | |||

altitude = |Z| - R * (1 - f) | altitude = |Z| - R * (1 - f) | |||

Appendix B. Calculating the Upward Normal of a Polygon | Appendix B. Calculating the Upward Normal of a Polygon | |||

End of changes. 18 change blocks. | ||||

43 lines changed or deleted | | 53 lines changed or added | ||

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