Google静态地图半径进行缩放 [英] Google static map radius to zoom

问题描述

我正在PHP中开发一个Web服务，该服务获取以公里为单位的纬度，经度和半径，并生成 Google静态地图.

I'm developing a web service in PHP that gets a latitude, longitude and a radius in kilometers and generate google static map.

我还显示了该半径范围内数据库中的所有点.

Also I display all points from my database in that radius.

我的问题是如何在Google的zoom参数中隐藏我的radius以确保所有点在地图上都可见?

My question is how I can covert my radius in google's zoom parameter to ensure that all points are visible on the map?

类似于:http://maps.googleapis.com/maps/api/staticmap?center=New+York,NY&[*THIS PARAMETER*zoom=13]&size=600x300&markers.......

推荐答案

如 Google Maps文档:

因为基本的Mercator Google地图图块是256 x 256像素.
另外请注意，每个缩放级别的地图都有2个 ⁿ 个图块.

Because the basic Mercator Google Maps tile is 256 x 256 pixels.
Also note that every zoom level, the map has 2 ⁿ tiles.

意味着在zoomLevel 2时，地图任意方向上的像素= 256 *2²= 1024px.

Meaning that at zoomLevel 2, the pixels in any direction of a map are = 256 * 2² = 1024px.

考虑到地球的周长约为40,000公里(以缩放0表示)，每个像素〜= 40,000 km/256 = 156.25 km
缩放9时，像素为131072:
1px = 40,000 km/131072 = 0.305 km ...

Taking into account that the earth has a perimeter of ~40,000 kilometers, in zoom 0, every pixel ~= 40,000 km/256 = 156.25 km
At zoom 9, pixels are 131072:
1px = 40,000 km / 131072 = 0.305 km ... and so on.

如果图像为640 x 640像素，并且正在使用缩放9，这意味着您将覆盖〜640 * 0.305〜= 195km.因此您的半径约为100公里.
每次缩放++时，半径都是一半.

If your image is 640 x 640 px,and you are using zoom 9, this means that you will cover ~ 640 * 0.305 ~= 195km. So your radius is approx 100km.
Everytime you zoom++, the radius is the half.

如果使用缩放15(1px = 0.00478km)，则图像将覆盖约3km宽(半径1.5km).

If you use zoom 15 (1px = 0.00478km) your image will cover ~3km wide (radius 1.5km).

请注意，随着您向北或向南移动，实际距离会更短，而失真会更大.

Take into account that as you go further to north or south, the real distance is less, as the distortion is bigger.

您可以将zoom = Floor(log ₂ (EarthP * 2 PixMap/(256 * radius)))作为参数使用.

You could use as parameter something like zoom = Floor(log₂ (EarthP * 2 PixMap / (256 *radius))).

• EarthP =该纬度处的地球周长(以公里为单位)
• PixMap =您将显示的地图像素
• 半径=要在图像中显示的半径(以公里为单位)
• log ₂ =以2为底的对数

• EarthP = Earth perimeter at that Latitude (in km)
• PixMap = Pixels of the map you will display
• radius = radius you want to be displayed in your image (in km)
• log ₂= logarithm in base 2

注意:要将log ₂ 转换为常规日志，只需执行以下操作:
Floor((log(EarthP * 2 PixMap/(256 * radius)))/log 2)

note: to convert log₂ into regular log just make this:
Floor((log (EarthP * 2 PixMap / (256 *radius)))/log 2)

维基百科中的对数的引用

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