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| <tr><td width=20><td><b>MAP(7)</b><td align=right><b>MAP(7)</b> |
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| <p><font size=+1><b>NAME </b></font><br> |
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| map – digitized map formats<br> |
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| <p><font size=+1><b>DESCRIPTION </b></font><br> |
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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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| <tt><font size=+1>struct {<br> |
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| signed char patchlatitude;<br> |
| signed char patchlongitude;<br> |
| short n;<br> |
| union {<br> |
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| struct {<br> |
| short latitude;<br> |
| short longitude;<br> |
| } point[n];<br> |
| struct {<br> |
| short latitude;<br> |
| short longitude;<br> |
| struct {<br> |
| signed char latdiff;<br> |
| signed char londiff;<br> |
| } point[–n];<br> |
| } highres;<br> |
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| </table> |
| } segment;<br> |
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| </table> |
| };<br> |
| </font></tt>where <tt><font size=+1>short</font></tt> stands for 16-bit integers and there is no padding |
| within or between <tt><font size=+1>structs</font></tt>. Shorts are stored in little-endian |
| order, low byte first. To assure portability, <i>map</i> accesses them |
| bytewise. |
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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 |
| by 10-degree patch of the earth’s surface a segment belongs. Their |
| values range from –9 to 8 and from –18 to 17, respectively, and |
| indicate the coordinates of the southeast corner of the patch |
| in units of 10 degrees. |
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| Each segment of |<tt><font size=+1>n</font></tt>| points is connected; consecutive segments |
| are not necessarily related. Latitude and longitude are measured |
| in units of 0.0001 radian. If <tt><font size=+1>n</font></tt> is negative, then differences |
| to the first and succeeding points are measured in units of 0.00001 |
| radian. Latitude is counted positive to the north and longitude |
| positive to the west. |
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| The patches are ordered lexicographically by <tt><font size=+1>patchlatitude</font></tt> then |
| <tt><font size=+1>patchlongitude</font></tt>. A printable index to the first segment of each |
| patch in a file named <i>data</i> is kept in an associated file named |
| <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> |
| and the byte position of the |
| patch in the map file. Both the map file and the index file are |
| ordered by patch latitude and longitude.<br> |
| |
| </table> |
| <p><font size=+1><b>SEE ALSO </b></font><br> |
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| <a href="../man7/map.html"><i>map</i>(7)</a><br> |
| The data comes from the World Data Bank I and II and U.S. Government |
| sources: the Census Bureau, Geological Survey, and CIA.<br> |
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