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1 <?xml version="1.0" encoding="utf-8"?> |
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2 <!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. --> |
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3 <!-- This component and the accompanying materials are made available under the terms of the License |
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4 "Eclipse Public License v1.0" which accompanies this distribution, |
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5 and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". --> |
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6 <!-- Initial Contributors: |
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7 Nokia Corporation - initial contribution. |
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8 Contributors: |
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9 --> |
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10 <!DOCTYPE concept |
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11 PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> |
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12 <concept id="GUID-AD7D9D39-6FF0-5811-9708-98538271BA0D" xml:lang="en"><title>Position |
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13 data</title><shortdesc>This document describes the basic and extended classes that hold |
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14 position data. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody> |
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15 <section><title>Purpose</title> <p>This document describes how position data |
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16 is represented within the <xref href="GUID-ABC01315-D65D-55EA-9D42-4DE6384D517D.dita">position |
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17 data classes</xref>. </p> </section> |
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18 <section><title>Values and co-ordinates</title> <ul> |
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19 <li id="GUID-23C5B7B1-8F7E-5E67-BFC5-8B6ADF2EC263"><p>The World Geodetic System |
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20 reference datum (WGS 84) is used by LBS. This is a global co-ordinate system |
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21 in which co-ordinates are expressed as latitude and longitude in degrees and |
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22 altitude in metres above the reference datum. In WGS 84, latitude values have |
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23 the range (-90 <= Lat <= +90) and longitude values have the range (-180 |
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24 <= Long < +180). </p> </li> |
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25 <li id="GUID-3F2BFE0F-29A1-516D-A27B-35298AD35FC8"><p>In LBS, latitude and |
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26 longitude are held as <codeph>TReal64</codeph> values and altitude is held |
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27 as a <codeph>TReal32</codeph> value. </p> </li> |
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28 <li id="GUID-EB9BEB2B-2CC2-5C70-9A88-4C9D80F42D0A"><p>Both horizontal and |
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29 vertical accuracy are held as <codeph>TReal32</codeph> values and represent |
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30 a possible error values in metres. </p> </li> |
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31 <li id="GUID-9909202F-8C8C-5EAA-814F-B9760CE63F6C"><p>Bearings and headings |
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32 are held as <codeph>TReal32</codeph> values and represent a direction in degrees. |
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33 Bearing and heading accuracies are also held as <codeph>TReal32</codeph> values |
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34 and represent a possible error value in degrees. </p> </li> |
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35 </ul> </section> |
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36 <section><title>Co-ordinate adjustment</title> <p>The <xref href="GUID-DDCBA817-9D88-3332-ABD3-1DDC6E397851.dita"><apiname>TCoordinate</apiname></xref> base |
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37 class holds the latitude, longitude and altitude of a position. If an application |
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38 attempts to assign values that are outside of the ranges specified by WGS |
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39 84 to an instance of a <codeph>TCoordinate</codeph> class then the values |
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40 are adjusted to lie within the correct interval. </p> </section> |
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41 <section><title>Unassigned values</title> <p>In some situations, one of the |
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42 position co-ordinates, typically altitude may not be known. This is usually |
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43 because the positioning module that was used to obtain the location fix was |
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44 unable to obtain data for that co-ordinate. Where LBS cannot assign a value |
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45 to a co-ordinate value, the value "Not a Number" (NaN) is assigned to it. |
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46 Applications must test for this situation by calling <xref href="GUID-1DB7AE7A-A505-3530-AC2B-EBAEFCD3F36A.dita#GUID-1DB7AE7A-A505-3530-AC2B-EBAEFCD3F36A/GUID-79B7EC5D-973E-3B91-91C4-48F10FC0038D"><apiname>Math::IsNaN()</apiname></xref> on |
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47 each returned co-ordinate value before using it in a calculation. </p> </section> |
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48 </conbody><related-links> |
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49 <link href="GUID-70E1117B-17F0-5CF4-A5D0-35D3BEBB0FEA.dita"><linktext>Position |
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50 Area Data Classes</linktext></link> |
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51 <link href="GUID-ACD9E338-DF75-5811-B696-C3900B498218.dita"><linktext>Privacy Requester |
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52 Classes</linktext></link> |
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53 </related-links></concept> |