kml - Google Earth KML 高度模式

Question

我对 google earth 的 kml 文件有疑问。当我使用高度模式 clampToGround 时，它完全符合我的预期，它很好地跟随地面。

<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://www.opengis.net/kml/2.2" xmlns:atom="http://www.w3.org/2005/Atom"    xmlns:gx="http://www.google.com/kml/ext/2.2" xmlns:kml="http://www.opengis.net/kml/2.2">
    <Document>
        <name>pm1kml</name>
        <Style id="poly">
            <LineStyle>
                <color>a000ff00</color>
            </LineStyle>
            <PolyStyle>
                <color>a000ff00</color>
        </PolyStyle>
    </Style>
    <Placemark>
        <styleUrl>#poly</styleUrl>
        <Polygon>
            <extrude>0</extrude>
            <tessellate>0</tessellate>
            <altitudeMode>clampToGround</altitudeMode>
            <outerBoundaryIs>
                <LinearRing>
                    <coordinates>-5.255885800498265,36.11513548688032,123 -5.257614986927059,36.097578762436825,123 -5.257614986927059,36.097578762436825,123 -5.262736094548725,36.08069673306777,123 -5.262736094548725,36.08069673306777,123 -5.27105232206931,36.06513816569425,123 -5.27105232206931,36.06513816569425,123 -5.282244081528993,36.051500967335095,123 -5.282244081528993,36.051500967335095,123 -5.29588127988815,36.04030920787541,123 -5.29588127988815,36.04030920787541,123 -5.311439847261665,36.03199298035483,123 -5.311439847261665,36.03199298035483,123 -5.3283218766307225,36.02687187273316,123 -5.3283218766307225,36.02687187273316,123 -5.345878601074219,36.02514268630436,123 -5.345878601074219,36.02514268630436,123 -5.363435325517715,36.02687187273316,123 -5.363435325517715,36.02687187273316,123 -5.380317354886772,36.03199298035483,123 -5.380317354886772,36.03199298035483,123 -5.395875922260288,36.04030920787541,123 -5.395875922260288,36.04030920787541,123 -5.409513120619445,36.051500967335095,123 -5.409513120619445,36.051500967335095,123 -5.4207048800791275,36.06513816569425,123 -5.4207048800791275,36.06513816569425,123 -5.429021107599713,36.08069673306777,123 -5.429021107599713,36.08069673306777,123 -5.434142215221378,36.097578762436825,123 -5.434142215221378,36.097578762436825,123 -5.435871401650172,36.11513548688032,123 -5.435871401650172,36.11513548688032,123 -5.434142215221378,36.132692211323814,123 -5.434142215221378,36.132692211323814,123 -5.429021107599713,36.14957424069287,123 -5.429021107599713,36.14957424069287,123 -5.4207048800791275,36.16513280806639,123 -5.4207048800791275,36.16513280806639,123 -5.409513120619445,36.178770006425545,123 -5.409513120619445,36.178770006425545,123 -5.395875922260288,36.18996176588523,123 -5.395875922260288,36.18996176588523,123 -5.380317354886771,36.19827799340581,123 -5.380317354886771,36.19827799340581,123 -5.363435325517715,36.20339910102748,123 -5.363435325517715,36.20339910102748,123 -5.345878601074219,36.205128287456276,123 -5.345878601074219,36.205128287456276,123 -5.3283218766307225,36.20339910102748,123 -5.3283218766307225,36.20339910102748,123 -5.311439847261665,36.19827799340581,123 -5.311439847261665,36.19827799340581,123 -5.29588127988815,36.18996176588523,123 -5.29588127988815,36.18996176588523,123 -5.282244081528993,36.178770006425545,123 -5.282244081528993,36.178770006425545,123 -5.27105232206931,36.16513280806639,123 -5.27105232206931,36.16513280806639,123 -5.262736094548725,36.14957424069287,123 -5.262736094548725,36.14957424069287,123 -5.257614986927059,36.132692211323814,123 -5.257614986927059,36.132692211323814,123 -5.255885800498265,36.11513548688032,123 -5.255885800498265,36.11513548688032,123 -5.255885800498265,36.11513548688032,123  </coordinates>
                </LinearRing>
            </outerBoundaryIs>
        </Polygon>
    </Placemark>
</Document>

然而，当我使用 relativeToGround 时，只有外部顶点跟随地面。在圆圈的中间，岩石位于绿色区域上方，而不是下方 123 米处。
图片:http://nl.tinypic.com/r/2vcsvq1/8

<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://www.opengis.net/kml/2.2" xmlns:atom="http://www.w3.org/2005/Atom"    xmlns:gx="http://www.google.com/kml/ext/2.2" xmlns:kml="http://www.opengis.net/kml/2.2">
    <Document>
        <name>pm1kml</name>
        <Style id="poly">
            <LineStyle>
                <color>a000ff00</color>
            </LineStyle>
            <PolyStyle>
                <color>a000ff00</color>
        </PolyStyle>
    </Style>
    <Placemark>
        <styleUrl>#poly</styleUrl>
        <Polygon>
            <extrude>0</extrude>
            <tessellate>0</tessellate>
            <altitudeMode>relativeToGround</altitudeMode>
            <outerBoundaryIs>
                <LinearRing>
                    <coordinates>-5.255885800498265,36.11513548688032,123 -5.257614986927059,36.097578762436825,123 -5.257614986927059,36.097578762436825,123 -5.262736094548725,36.08069673306777,123 -5.262736094548725,36.08069673306777,123 -5.27105232206931,36.06513816569425,123 -5.27105232206931,36.06513816569425,123 -5.282244081528993,36.051500967335095,123 -5.282244081528993,36.051500967335095,123 -5.29588127988815,36.04030920787541,123 -5.29588127988815,36.04030920787541,123 -5.311439847261665,36.03199298035483,123 -5.311439847261665,36.03199298035483,123 -5.3283218766307225,36.02687187273316,123 -5.3283218766307225,36.02687187273316,123 -5.345878601074219,36.02514268630436,123 -5.345878601074219,36.02514268630436,123 -5.363435325517715,36.02687187273316,123 -5.363435325517715,36.02687187273316,123 -5.380317354886772,36.03199298035483,123 -5.380317354886772,36.03199298035483,123 -5.395875922260288,36.04030920787541,123 -5.395875922260288,36.04030920787541,123 -5.409513120619445,36.051500967335095,123 -5.409513120619445,36.051500967335095,123 -5.4207048800791275,36.06513816569425,123 -5.4207048800791275,36.06513816569425,123 -5.429021107599713,36.08069673306777,123 -5.429021107599713,36.08069673306777,123 -5.434142215221378,36.097578762436825,123 -5.434142215221378,36.097578762436825,123 -5.435871401650172,36.11513548688032,123 -5.435871401650172,36.11513548688032,123 -5.434142215221378,36.132692211323814,123 -5.434142215221378,36.132692211323814,123 -5.429021107599713,36.14957424069287,123 -5.429021107599713,36.14957424069287,123 -5.4207048800791275,36.16513280806639,123 -5.4207048800791275,36.16513280806639,123 -5.409513120619445,36.178770006425545,123 -5.409513120619445,36.178770006425545,123 -5.395875922260288,36.18996176588523,123 -5.395875922260288,36.18996176588523,123 -5.380317354886771,36.19827799340581,123 -5.380317354886771,36.19827799340581,123 -5.363435325517715,36.20339910102748,123 -5.363435325517715,36.20339910102748,123 -5.345878601074219,36.205128287456276,123 -5.345878601074219,36.205128287456276,123 -5.3283218766307225,36.20339910102748,123 -5.3283218766307225,36.20339910102748,123 -5.311439847261665,36.19827799340581,123 -5.311439847261665,36.19827799340581,123 -5.29588127988815,36.18996176588523,123 -5.29588127988815,36.18996176588523,123 -5.282244081528993,36.178770006425545,123 -5.282244081528993,36.178770006425545,123 -5.27105232206931,36.16513280806639,123 -5.27105232206931,36.16513280806639,123 -5.262736094548725,36.14957424069287,123 -5.262736094548725,36.14957424069287,123 -5.257614986927059,36.132692211323814,123 -5.257614986927059,36.132692211323814,123 -5.255885800498265,36.11513548688032,123 -5.255885800498265,36.11513548688032,123 -5.255885800498265,36.11513548688032,123  </coordinates>
                </LinearRing>
            </outerBoundaryIs>
        </Polygon>
    </Placemark>
</Document>

我需要的是 clampToGround 中的多边形提升 123 米。这对 google earth 的 kml 文件是否可行。如果是这样，我该怎么做？
提前致谢!

编辑:它已经被报告为一个问题:https://code.google.com/p/kml-samples/issues/detail?id=432

Answer 1

KML 规范中定义的 clampToGround 和 relativeToGround 之间存在明显的行为差异。

根据定义，

clampToGround 遵循地形，如果多边形与地形相交，它会包裹山脉或丘陵的表面。

另一方面，

relativeToGround 创建了一个平行于地面的平面，该平面穿过任何山脉和丘陵，如下图所示。 123 米的 relativeToGround 是地面高程 123，不高于岩石顶部。相对于地面零高程是这个实例是岩石的底部。

直布罗陀岩石在山顶高出地面约 390 米，因此岩石的相对高度为 123 米。如果您希望多边形位于岩石尖端上方 123 米处，那么您应该将相对高度设置为 ~513 米，这就像该位置上方低垂的绿云。

或者，如果您想要用绿色多边形包裹岩石的顶部，并且多边形的平面高出 123 米(切穿岩石)，那么建议您定义一个 MultiGeometry第二个多边形带有 relativeToGround(如上所列)和一个较小的圆圈，它刚好覆盖了 altitudeMode=clampToGround 的岩石尖端。

<MultiGeometry>
 <Polygon>
  <altitudeMode>relativeToGround</altitudeMode>
  ... use coordinates of original polygon here
 </Polygon>
 <Polygon>
  <altitudeMode>clampToGround</altitudeMode>
  ... use coordinates of smaller polygon here
 </Polygon>
</MultiGeometry>

但是，如果您希望多边形遵循地形形状但高于地面的 clampToGround 行为，则需要在 relativeToGround 模式下创建小的多边形网格。