WMS作为Google Maps v3中的单个平铺图片 [英] WMS as a single tile image in Google Maps v3

问题描述

我遵循 http://www.gisdoctor.com/v3/mapserver上的代码。 HTML 将WMS作为图像叠加在使用API​​ v3的Google地图上。上面链接的js代码如下所示：
$ b $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ projection = map.getProjection（）;
var zpow = Math.pow（2，zoom）;
var ul = new google.maps.Point（
tile.x * 256.0 / zpow，
（tile.y + 1）* 256.0 / zpow
）;
var lr = new google.maps.Point（
（tile.x + 1）* 256.0 / zpow，
tile.y * 256.0 / zpow
）;
var ulw = projection.fromPointToLatLng（ul）;
var lrw = projection.fromPointToLatLng（lr）;

var bbox = ulw.lng（）+，+ ulw.lat（）+，+ lrw.lng（）+，+ lrw.lat（）;

return url =http：// url / to / mapserver？ +
版本= 1.1.1& +
request = GetMap& +
样式=默认值& +
SRS = EPSG：4326& +
图层= wmsLayers& +
BBOX =+ bbox +& +
width = 256& +
height = 256& +
format = image / png& +
TRANSPARENT = TRUE;
}，

addWmsLayer：function（）{

/ *
创建WMS图层选项。此代码为每个wms图层创建Google
imagemaptype选项。在选项中，调用单个wms层的函数
被设置为
* /
var wmsOptions = {
alt：MapServer Layers，
getTileUrl：WMSGetTileUrl，
isPng：false，
maxZoom：17，
minZoom：1，
name：MapServer Layer，
tileSize：new google.maps.Size（256， 256）
};

/ *
创建对象以创建将调用WMS
图层选项的ImageMapType。
* /
wmsMapType = new google.maps.ImageMapType（wmsOptions）;
map.overlayMapTypes.insertAt（0，wmsMapType）;
}，

一切正常，但是，WMS当然会返回为256 x 256个瓷砖。没有惊喜，因为这就是我所要求的。但是，在 http：/ /groups.google.com/group/google-maps-js-api-v3/browse_thread/thread/c22837333f9a1812/d410a2a453025b38 ，似乎我可能会更好地向mapserver请求一个不带色的（单个）图像。这会减少我的服务器。无论如何，我想尝试一个单一的图像，但我无法正确构建一个请求。

具体来说，我改变了瓷砖的大小到一些大的东西;例如，我尝试了1024 x 1024的图块。我确实获得了较少的图块，但返回的图像与Google Maps基本图层边界不匹配。

我想要的是根本不指定图块大小。相反，我应该动态地确定图块的大小，例如比当前地图大小大256个像素。这样，无论地图大小如何，都会返回单个图像。此外，在地图边缘的额外256像素的帮助下，可以实现无缝平移。

建议？

解决方案

请参阅同样的问题我刚刚为其他人回答。这很可能是你的预测。 EPSG：4326不是Google地图的正确投影。改变投影意味着你需要改变坐标计算和引用的方式。

I am following the code at http://www.gisdoctor.com/v3/mapserver.html to overlay a WMS as an image on Google Maps using API v3. The js code at the above link is as follows

"WMSGetTileUrl" : function(tile, zoom) {
    var projection = map.getProjection();
    var zpow = Math.pow(2, zoom);
    var ul = new google.maps.Point(
        tile.x * 256.0 / zpow, 
        (tile.y + 1) * 256.0 / zpow
    );
    var lr = new google.maps.Point(
        (tile.x + 1) * 256.0 / zpow, 
        tile.y * 256.0 / zpow
    );
    var ulw = projection.fromPointToLatLng(ul);
    var lrw = projection.fromPointToLatLng(lr);

    var bbox = ulw.lng() + "," + ulw.lat() + "," + lrw.lng() + "," + lrw.lat();

    return url = "http://url/to/mapserver?" + 
        "version=1.1.1&" + 
        "request=GetMap&" + 
        "Styles=default&" + 
        "SRS=EPSG:4326&" + 
        "Layers=wmsLayers&" + 
        "BBOX=" + bbox + "&" + 
        "width=256&" + 
        "height=256&" + 
        "format=image/png&" + 
        "TRANSPARENT=TRUE";
},

"addWmsLayer" : function() {

    /*
    Creating the WMS layer options. This code creates the Google 
    imagemaptype options for each wms layer. In the options the function 
    that calls the individual wms layer is set 
    */
    var wmsOptions = {
        alt: "MapServer Layers",
        getTileUrl: WMSGetTileUrl,
        isPng: false,
        maxZoom: 17,
        minZoom: 1,
        name: "MapServer Layer",
        tileSize: new google.maps.Size(256, 256)
    };

    /*
    Creating the object to create the ImageMapType that will call the WMS 
    Layer Options. 
    */
    wmsMapType = new google.maps.ImageMapType(wmsOptions);
    map.overlayMapTypes.insertAt(0, wmsMapType);
},

Everything works fine, but, of course, the WMS is returned as 256 x 256 tiles. No surprises, because that is what I requested. However, following the discussion at http://groups.google.com/group/google-maps-js-api-v3/browse_thread/thread/c22837333f9a1812/d410a2a453025b38 it seems that I might be better off requesting an untiled (single) image from mapserver. This would tax my server less. In any case, I would like to experiment with a single image, but I am unable to construct a request for one properly.

Specifically, I changed the size of the tile to something large; for example, I tried 1024 x 1024 tiles. I did get fewer tiles, but the returned images didn't match the Google Maps base layer boundaries.

What I would like is to not specify the tile size at all. Instead, I should dynamically figure out the tile size to be, say, 256 pixels bigger than the current map size. That way, a single image would be returned, no matter what the map size. Also, a seamless pan would be implemented with the help of the extra 256px along the map edges.

Suggestions?

解决方案

See this same question I just answered for someone else. It's likely to be your projection. EPSG:4326 is not the correct projection for Google Maps. Changing the projection means you need to change the way coordinates are calculated and referenced.

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