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Google maps切割方法 每个切割的小图片是256*256（像素）

<DIV align=center><FONT size=2>7,864,320</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>30G</FONT></DIV></TD></TR>
<TR>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>4级</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>1:50,000</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>1,966,080</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>7.5G</FONT></DIV></TD></TR>
<TR>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>5级</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>1:100,000</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>491,520</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>1.875G</FONT></DIV></TD></TR>
<TR>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>6级</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>1:250,000</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>122,880</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2></FONT></DIV></TD></TR>
<TR>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>7级</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>1:500,000</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>30,720</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2></FONT>&nbsp;</DIV></TD></TR>
<TR>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>8级</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>1:1,000,000</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>7,680</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2></FONT>&nbsp;</DIV></TD></TR>
<TR>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>9级</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>1:2,500,000</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>1,920</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2></FONT>&nbsp;</DIV></TD></TR>
<TR>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>10级</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>1:5,000,000</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>480</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2></FONT>&nbsp;</DIV></TD></TR>
<TR>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>11级</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>1:10,000,000</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>120</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2></FONT>&nbsp;</DIV></TD></TR>
<TR>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>12级</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>1:50,000,000</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2>30</FONT></DIV></TD>
<TD vAlign=top width="25%">
<DIV align=center><FONT size=2></FONT>&nbsp;</DIV></TD></TR></TBODY></TABLE>
<P class=MsoNormal style="MARGIN-LEFT: 21pt; TEXT-INDENT: 21pt"><SPAN style="FONT-FAMILY: 宋体">由以上分析可见在大比例尺下若全部生成</SPAN><SPAN lang=EN-US>,</SPAN><SPAN style="FONT-FAMILY: 宋体">其数量是很巨大的</SPAN><SPAN lang=EN-US>,</SPAN><SPAN style="FONT-FAMILY: 宋体">考虑到某些大比例尺地图只是在某些地区或特殊要求时是必须的</SPAN><SPAN lang=EN-US>,</SPAN><SPAN style="FONT-FAMILY: 宋体">我们没有必要全部生成</SPAN><SPAN lang=EN-US>,</SPAN><SPAN style="FONT-FAMILY: 宋体">只需生成规定经纬度范围内的某一缩放级别下的地图。但即使这样小缩放级别下的图幅数量仍然不小</SPAN><SPAN lang=EN-US>,</SPAN><SPAN style="FONT-FAMILY: 宋体">所以我们应该分区域在不同文件夹下存放。从级别</SPAN><SPAN lang=EN-US>n</SPAN><SPAN style="FONT-FAMILY: 宋体">到级别</SPAN><SPAN lang=EN-US>n+1,</SPAN><SPAN style="FONT-FAMILY: 宋体">图片数量后者是前者的</SPAN><SPAN lang=EN-US>4</SPAN><SPAN style="FONT-FAMILY: 宋体">倍</SPAN><SPAN lang=EN-US>,</SPAN><SPAN style="FONT-FAMILY: 宋体">即放大一个级别原级别一张图片裂变为四张</SPAN><SPAN lang=EN-US>,</SPAN><SPAN style="FONT-FAMILY: 宋体">这样我们可以借鉴四杈树的组织形式</SPAN><SPAN lang=EN-US>,</SPAN><SPAN style="FONT-FAMILY: 宋体">即若树的深度为</SPAN><SPAN lang=EN-US>N,</SPAN><SPAN style="FONT-FAMILY: 宋体">深度为</SPAN><SPAN lang=EN-US>N-1</SPAN><SPAN style="FONT-FAMILY: 宋体">的节点子节点均为</SPAN><SPAN lang=EN-US>30</SPAN><SPAN style="FONT-FAMILY: 宋体">个</SPAN><SPAN lang=EN-US>,</SPAN><SPAN style="FONT-FAMILY: 宋体">其余节点子节点为四个</SPAN><SPAN lang=EN-US>(</SPAN><SPAN style="FONT-FAMILY: 宋体">当深度为</SPAN><SPAN lang=EN-US>1</SPAN><SPAN style="FONT-FAMILY: 宋体">时</SPAN><SPAN lang=EN-US>,</SPAN><SPAN style="FONT-FAMILY: 宋体">根结点子节点为</SPAN><SPAN lang=EN-US>5*6=30</SPAN><SPAN style="FONT-FAMILY: 宋体">个</SPAN><SPAN lang=EN-US>),</SPAN><SPAN style="FONT-FAMILY: 宋体">树的深度与缩放级别的对应关系为</SPAN><SPAN lang=EN-US>N=13-n</SPAN><SPAN style="FONT-FAMILY: 宋体">。</SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21pt; TEXT-INDENT: 21pt"><SPAN style="FONT-FAMILY: 宋体">树的节点的命名即为对应文件夹的名称，根结点即以缩放级别命名，叶节点对应图片以形如“</SPAN><SPAN lang=EN-US>bx-by.png</SPAN><SPAN style="FONT-FAMILY: 宋体">”的形式命名，其它节点则是形如“</SPAN><SPAN lang=EN-US>0-0</SPAN><SPAN style="FONT-FAMILY: 宋体">”、“</SPAN><SPAN lang=EN-US>0-1</SPAN><SPAN style="FONT-FAMILY: 宋体">”、“</SPAN><SPAN lang=EN-US>1-0</SPAN><SPAN style="FONT-FAMILY: 宋体">”、“</SPAN><SPAN lang=EN-US>1-1</SPAN><SPAN style="FONT-FAMILY: 宋体">”的形式命名。</SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21pt; TEXT-INDENT: 21pt"><SPAN style="FONT-FAMILY: 宋体">这样一来生成图片的时候就有一个路径判断和生成的问题。在确定了经度跨度为【</SPAN><SPAN lang=EN-US>67.5</SPAN><SPAN style="FONT-FAMILY: 宋体">，</SPAN><SPAN lang=EN-US>135</SPAN><SPAN style="FONT-FAMILY: 宋体">】，纬度跨度为【</SPAN><SPAN lang=EN-US>0</SPAN><SPAN style="FONT-FAMILY: 宋体">，</SPAN><SPAN lang=EN-US>56.25</SPAN><SPAN style="FONT-FAMILY: 宋体">】，并且在最小比例尺（缩放等级为</SPAN><SPAN lang=EN-US>12</SPAN><SPAN style="FONT-FAMILY: 宋体">）之下我们已知图片是</SPAN><SPAN lang=EN-US>5*6</SPAN><SPAN style="FONT-FAMILY: 宋体">张，即经度方向为</SPAN><SPAN lang=EN-US>6</SPAN><SPAN style="FONT-FAMILY: 宋体">，纬度方向为</SPAN><SPAN lang=EN-US>5</SPAN><SPAN style="FONT-FAMILY: 宋体">，这两个值很重要直接影响到我们的命名，当然前提变了这个值也随着变了。我们制定规则如下：</SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21pt; TEXT-INDENT: 21pt"><SPAN style="FONT-FAMILY: 宋体">如前树的深度为</SPAN><SPAN lang=EN-US>N</SPAN><SPAN style="FONT-FAMILY: 宋体">，经度方向上的序号为</SPAN><SPAN lang=EN-US>bx,</SPAN><SPAN style="FONT-FAMILY: 宋体">纬度方向上的序号为</SPAN><SPAN lang=EN-US>by</SPAN><SPAN style="FONT-FAMILY: 宋体">。则当</SPAN><SPAN lang=EN-US>1&lt;N&lt;max(N)</SPAN><SPAN style="FONT-FAMILY: 宋体">时，经度方向上的节点值</SPAN><SPAN lang=EN-US>Lng</SPAN><SPAN style="FONT-FAMILY: 宋体">＝</SPAN><SPAN lang=EN-US>ToString(((bx-7*N)/6)%2), </SPAN><SPAN style="FONT-FAMILY: 宋体">纬度方向上的节点值</SPAN><SPAN lang=EN-US>Lat</SPAN><SPAN style="FONT-FAMILY: 宋体">＝</SPAN><SPAN lang=EN-US>ToString((by/5)%2),</SPAN><SPAN style="FONT-FAMILY: 宋体">则节点名称命名为</SPAN><SPAN lang=EN-US>Lng+”-”+Lat</SPAN><SPAN style="FONT-FAMILY: 宋体">。</SPAN><BR></P>