3

我下载了一个小区域的 Open Street Map 数据,我想过滤数据以获取具有特殊类别的节点。

这是 OSM 数据的示例

 <node id="505126369" lat="31.2933856" lon="34.2687443" user="JumpStart International" uid="125156" visible="true" version="1" changeset="2568758" timestamp="2009-09-22T13:05:10Z"/>
 <node id="505126372" lat="31.2682934" lon="34.2745680" user="JumpStart International" uid="125156" visible="true" version="1" changeset="2568758" timestamp="2009-09-22T13:05:10Z"/>
 <node id="505126375" lat="31.2953082" lon="34.3471630" user="JumpStart International" uid="125156" visible="true" version="1" changeset="2568758" timestamp="2009-09-22T13:05:10Z"/>
 <node id="505126378" lat="31.2807872" lon="34.2757999" user="JumpStart International" uid="125156" visible="true" version="1" changeset="2568758" timestamp="2009-09-22T13:05:11Z">
   <tag k="amenity" v="school"/>
   <tag k="name" v="Al Aqqad Basic &amp; Secondary Female School"/>
   <tag k="name:ar" v="مدرسة العقاد الأساسية والثانوية للبنات"/>
  </node>

我想获得整个学校、医院的数据。

如果有人使用 PHP 或 Java 进行过 XML 解析,我将非常感谢与我和所有感兴趣的人分享它。

编辑 这是一个简单的开始,我刚刚

$dataFile = base_url() . 'media/files/osmdata/map_3.xml';
    //echo ($dataFile);

    $xml = simplexml_load_file($dataFile);

    //    $countTotal = count($xml->node);
    //   echo 'here'.$countTotal;
    foreach ($xml as $key => $val) {
        var_dump($val);
               // can't manage things overs here

    }
4

1 回答 1

8

以下是我编译的一个带有 PHP SimpleXML 的 OSM Overpass API 小示例,因为我们这里没有 PHP 并且我喜欢 OSM,所以让我们展示一些有用的示例。

第一部分展示了如何使用标准 PHP 查询 Overpass Endpoint。您不需要该部分,因为您已经将数据保存在硬盘上:

<?php
/**
 * OSM Overpass API with PHP SimpleXML / XPath
 *
 * PHP Version: 5.4 - Can be back-ported to 5.3 by using 5.3 Array-Syntax (not PHP 5.4's square brackets)
 */


//
// 1.) Query an OSM Overpass API Endpoint
//

$query = 'node
  ["amenity"~".*"]
  (38.415938460513274,16.06338500976562,39.52205163048525,17.51220703125);
out;';

$context = stream_context_create(['http' => [
    'method'  => 'POST',
    'header' => ['Content-Type: application/x-www-form-urlencoded'],
    'content' => 'data=' . urlencode($query),
]]);

# please do not stress this service, this example is for demonstration purposes only.
$endpoint = 'http://overpass-api.de/api/interpreter';
libxml_set_streams_context($context);
$start = microtime(true);

$result = simplexml_load_file($endpoint);
printf("Query returned %2\$d node(s) and took %1\$.5f seconds.\n\n", microtime(true) - $start, count($result->node));

对你来说,第二部分更有趣。那就是查询您已经拥有的 XML 数据。使用 xpath 最容易做到这一点,使用的 PHP XML 库基于 libxml,它支持XPath 1.0,它很好地涵盖了各种查询需求。

以下示例列出了所有学校并尝试获取它们的名称。我还没有涵盖翻译,因为我的示例数据没有这些,但您也可以查找包括翻译在内的所有类型的名称,并且只喜欢特定的名称):

//
// 2.) Work with the XML Result
//

# get all school nodes with xpath
$xpath = '//node[tag[@k = "amenity" and @v = "school"]]';
$schools = $result->xpath($xpath);
printf("%d School(s) found:\n", count($schools));
foreach ($schools as $index => $school)
{
    # Get the name of the school (if any), again with xpath
    list($name) = $school->xpath('tag[@k = "name"]/@v') + ['(unnamed)'];
    printf("#%02d: ID:%' -10s  [%s,%s]  %s\n", $index, $school['id'], $school['lat'], $school['lon'], $name);
}

这里的关键点是 xpath 查询。使用了两个,第一个用于获取具有特定标签的节点。我认为这对你来说是最有趣的:

//node[tag[@k = "amenity" and @v = "school"]]

这行说:给我所有的节点元素,其中有一个标签元素,其中k属性值"amenity"v属性值"school"。这是您必须过滤掉那些标有 amenity school的节点的条件。

再次使用 xpath,现在相对于那些学校节点查看是否有名称,如果有,则获取它:

tag[@k = "name"]/@v'

这一行说:相对于当前节点,给我来自标签元素的v属性,作为k属性值"name"。如您所见,某些部分再次与之前的行相似。我认为你们都可以根据自己的需要采用它们。

因为并非所有学校节点都有名称,所以通过将默认字符串添加到(然后为空)结果数组中来提供默认字符串以供显示:

list($name) = $school->xpath('tag[@k = "name"]/@v') + ['(unnamed)'];
                                                    ^^^^^^^^^^^^^^^
                                                Provide Default Value

所以这里是我对该代码示例的结果:

Query returned 907 node(s) and took 1.10735 seconds.
10 School(s) found:
#00: ID:332534486   [39.5017565,16.2721899]  Scuola Primaria
#01: ID:1428094278  [39.3320912,16.1862820]  (unnamed)
#02: ID:1822746784  [38.9075566,16.5776597]  (unnamed)
#03: ID:1822755951  [38.9120272,16.5713431]  (unnamed)
#04: ID:1903859699  [38.6830409,16.5522243]  Liceo Scientifico Statale A. Guarasci
#05: ID:2002566438  [39.1347698,16.0736924]  (unnamed)
#06: ID:2056891127  [39.4106679,16.8254844]  (unnamed)
#07: ID:2056892999  [39.4124687,16.8286119]  (unnamed)
#08: ID:2272010226  [39.4481717,16.2894353]  SCUOLA DELL'INFANZIA SAN FRANCESCO
#09: ID:2272017152  [39.4502366,16.2807664]  SCUOLA MEDIA 

我希望这已经很有用了,如果您有更多澄清问题,请告诉我。


(by rbwilkinson):这是您可以添加其他参数以查找其他值的方式。以下示例查找一公里内的其他属性:

$query = 'node
  ["addr:postcode"~"RM12"]
  (51.5557914,0.2118915,51.5673083,0.2369398);
   node
  (around:1000)
  ["amenity"~"fast_food"];
           out;';

$context = stream_context_create(['http' => [
    'method'  => 'POST',
    'header' => ['Content-Type: application/x-www-form-urlencoded'],
    'content' => 'data=' . urlencode($query),
]]);

$endpoint = 'http://overpass-api.de/api/interpreter';
libxml_set_streams_context($context);

$result = simplexml_load_file($endpoint);
printf("Query returned %2\$d node(s) and took %1\$.5f seconds.\n\n", microtime(true) - $start, count($result->node));
}
于 2013-04-21T12:35:21.653 回答