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108 lines
4.2 KiB
HTML
108 lines
4.2 KiB
HTML
<head>
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<title>map(7) - Plan 9 from User Space</title>
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<meta content="text/html; charset=utf-8" http-equiv=Content-Type>
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</head>
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<body bgcolor=#ffffff>
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<table border=0 cellpadding=0 cellspacing=0 width=100%>
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<tr height=10><td>
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<tr><td width=20><td>
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<tr><td width=20><td><b>MAP(7)</b><td align=right><b>MAP(7)</b>
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<tr><td width=20><td colspan=2>
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<br>
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<p><font size=+1><b>NAME </b></font><br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
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map – digitized map formats<br>
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</table>
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<p><font size=+1><b>DESCRIPTION </b></font><br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
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Files used by <a href="../man7/map.html"><i>map</i>(7)</a> are a sequence of structures of the form:
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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<tt><font size=+1>struct {<br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
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signed char patchlatitude;<br>
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signed char patchlongitude;<br>
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short n;<br>
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union {<br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
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struct {<br>
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short latitude;<br>
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short longitude;<br>
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} point[n];<br>
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struct {<br>
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short latitude;<br>
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short longitude;<br>
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struct {<br>
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signed char latdiff;<br>
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signed char londiff;<br>
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} point[–n];<br>
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} highres;<br>
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</table>
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} segment;<br>
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</table>
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};<br>
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</font></tt>where <tt><font size=+1>short</font></tt> stands for 16-bit integers and there is no padding
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within or between <tt><font size=+1>structs</font></tt>. Shorts are stored in little-endian
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order, low byte first. To assure portability, <i>map</i> accesses them
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bytewise.
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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Fields <tt><font size=+1>patchlatitude</font></tt> and <tt><font size=+1>patchlongitude</font></tt> tell to what 10-degree
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by 10-degree patch of the earth’s surface a segment belongs. Their
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values range from –9 to 8 and from –18 to 17, respectively, and
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indicate the coordinates of the southeast corner of the patch
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in units of 10 degrees.
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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Each segment of |<tt><font size=+1>n</font></tt>| points is connected; consecutive segments
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are not necessarily related. Latitude and longitude are measured
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in units of 0.0001 radian. If <tt><font size=+1>n</font></tt> is negative, then differences
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to the first and succeeding points are measured in units of 0.00001
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radian. Latitude is counted positive to the north and longitude
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positive to the west.
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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The patches are ordered lexicographically by <tt><font size=+1>patchlatitude</font></tt> then
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<tt><font size=+1>patchlongitude</font></tt>. A printable index to the first segment of each
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patch in a file named <i>data</i> is kept in an associated file named
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<i>data</i><tt><font size=+1>.x</font></tt>. Each line of an index file contains <tt><font size=+1>patchlatitude, patchlongitude</font></tt>
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and the byte position of the
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patch in the map file. Both the map file and the index file are
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ordered by patch latitude and longitude.<br>
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</table>
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<p><font size=+1><b>SEE ALSO </b></font><br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
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<a href="../man7/map.html"><i>map</i>(7)</a><br>
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The data comes from the World Data Bank I and II and U.S. Government
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sources: the Census Bureau, Geological Survey, and CIA.<br>
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</table>
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<td width=20>
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<tr height=20><td>
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</table>
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<!-- TRAILER -->
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<table border=0 cellpadding=0 cellspacing=0 width=100%>
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<tr height=15><td width=10><td><td width=10>
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<tr><td><td>
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<center>
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<a href="../../"><img src="../../dist/spaceglenda100.png" alt="Space Glenda" border=1></a>
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</center>
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</table>
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<!-- TRAILER -->
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</body></html>
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