iOS如何在每个区域（任何位置和任何缩放）计算尺寸宽度到米 [英] iOS how to calculate size width to meters in every region(any location and any zoom)

问题描述

像标题一样，是否有人知道如何在每个区域计算尺寸宽度到米，意味着在每个地方和任何缩放。

我找到了如何获得zoomScale。

  CLLocationDegrees longitudeDelta = myMapView.region.span.longitudeDelta; 
 CGFloat mapWidthInPixels = myMapView.bounds.size.width; 
 double zoomScale = longitudeDelta * MERCATOR_RADIUS * M_PI /（180.0 * mapWidthInPixels）; 
  

但我不知道结果意味着什么，如果我想得到尺寸宽度的米或者是20f行，我将 mapWidthInPixels 更改为20是否正确？

解决方案

你可以在这里找到一个详细的公式解释：将经度纬度转换为米。

示例代码：

  CLLocationDegrees deltaLatitude = self.mapView.region.span。 latitudeDelta; 
 CLLocationDegrees deltaLongitude = self.mapView.region.span.longitudeDelta; 
 CGFloat latitudeCircumference = 40075160 * cos（self.mapView.region.center.latitude * M_PI / 180）; 
 NSLog（@x：％f; y：％f，deltaLongitude * latitudeCircumference / 360，deltaLatitude * 40008000/360）; 
  

马克赎金

like the title, does any one know how to calculate size width to meters in every region, means in every where and any zoom.

I found how to get the zoomScale.

CLLocationDegrees longitudeDelta = myMapView.region.span.longitudeDelta;
CGFloat mapWidthInPixels = myMapView.bounds.size.width;
double zoomScale = longitudeDelta * MERCATOR_RADIUS * M_PI / (180.0 * mapWidthInPixels);

But I don't know what does result mean, if I want to get the meters for size width or maybe a line 20f, I change the mapWidthInPixels to 20 does it right?

解决方案

You can find an elaborate explanation of the formula here: transform longitude latitude into meters.

Sample code:

CLLocationDegrees deltaLatitude = self.mapView.region.span.latitudeDelta;
CLLocationDegrees deltaLongitude = self.mapView.region.span.longitudeDelta;
CGFloat latitudeCircumference = 40075160 * cos(self.mapView.region.center.latitude * M_PI / 180);
NSLog(@"x: %f; y: %f", deltaLongitude * latitudeCircumference / 360, deltaLatitude * 40008000 / 360);

Credits to Mark Ransom

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