计算谷歌地图的视口？ [英] Calculating Google map's viewport?

问题描述

我做了一些使用谷歌本地搜索的地理编码，并需要能够设置一个谷歌地图API V3对象的视口的页面上。

I'm doing a bit of geocoding using Google Local Search and need to be able to set the viewport of a google maps api v3 object on the page.

现在这是好的，如果因为它为后code或街道谷歌本地搜索返回我一个很好的视口，但如果我把例如一个酒吧的名字。返回视口是非常大的presumable因为本地搜索已经发现了很多的比赛，但已经恢复最好的。

Now this is fine if google local search has returned me a good viewport as it does for a postcode or street but if i put in the name of a bar for example. The viewport returned is very large presumable because local search has found many matches but has returned the best.

我想计算在这种情况下我自己的视口，我在下面的方式这样做的：

I'd like to calculate my own viewport in this case and am doing so in the following manner:

result.Centre = new LatLon(double.Parse(lat),double.Parse(lon));
result.Span = new LatLon(0.006295d, 0.008407d);
string viewport = "{{\"center\":{{\"lat\":\"{0}\",\"lng\":\"{1}\"}},\"span\":{{\"lat\":\"{2}\",\"lng\":\"{3}\"}},\"sw\":{{\"lat\":\"{4}\",\"lng\":\"{5}\"}},\"ne\":{{\"lat\":\"{6}\",\"lng\":\"{7}\"}}}}";
//Calculate the south west by taking half the span and adding it to the centre
double swLat = result.Centre.Latitude + (result.Span.Latitude/2);
double swLon = result.Centre.Longitude + (result.Span.Longitude/2);
//and northeast corners by taking half the span and subtracting from the centre
double neLat = result.Centre.Latitude - (result.Span.Latitude/2);
double neLon = result.Centre.Longitude - (result.Span.Longitude/2);


//Fingers crossed :)
result.ViewPortJSON = string.Format(viewport, result.Centre.Latitude, result.Centre.Longitude,result.Span.Latitude, result.Span.Longitude, swLat, swLon,neLat, neLon);

问题是我得到一些有效的JSON但谷歌地图会放大右出，所以我可以看到整个世界。同样的code在前端被用作如果谷歌给我的视口，以便我不明白是怎么回事。

The problem is I get some valid json but google maps zooms right out so I can see the whole world. The same code is being used at the front end as if google has given me the viewport so I don't understand what is going on.

任何想法？有我有我的算盘打错了？我曾尝试与整个跨度（即假设它已经是一个半径）具有同样的效果。

Any ideas? Have I got my calculations wrong? I have tried with the whole span (i.e. assuming it is already a radius) with the same effect.

先谢谢了。

推荐答案

哎，你不应该做：

double swLat = result.Centre.Latitude - (result.Span.Latitude/2); 

double swLon = result.Centre.Longitude - (result.Span.Longitude/2); 

//and northeast corners by taking half the span and subtracting from the centre 

double neLat = result.Centre.Latitude + (result.Span.Latitude/2); 

double neLon = result.Centre.Longitude + (result.Span.Longitude/2);

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