谷歌街景原理_图文-课件·PPT.ppt

谷歌街景原理
Creating Custom Panoramas
Each Street View panorama is an image or set of images that provides a full 360 degree view from a single location. The Street View Panorama object uses images that conform to the equirectangular (Plate Carrée) projection. Such a projection contains 360 degrees of horizontal view (a full wrap-around) and 180 degrees of vertical view (from straight up to straight down). These fields of view result in an image with an aspect ratio of 2:1. A full wrap-around panorama is shown below.
每一个谷歌街景(Street View)全景照片其实是一张或一组提供了从一个地点360度全景视角的照片。街景全景照片是用了遵循“等矩形投影”(equirectangular (Plate Carrée) projection)的图片。这样的一个投影包括了一个360度的水平视野(完整地绕一周)和一个180度的垂直视野(从正上方到正下方)。这样的视野(fields of view)形成了一张宽高比为2:1的图片。
一张完整的环绕一周的全景照片
Panorama images are generally obtained by taking multiple photos from one position and stitching them together using panorama software. Such images should share a single "camera" locus, from which each of the panorama images are taken. The resulting 360 degree panorama can then define a projection on a sphere with the image wrapped to the two-dimensional surface of the sphere.
全景照片通常是通过从一个位置拍多张照片并用全景图片软件将它们拼接在一起制作而成的。要拍摄这一组全景照片应当让相机安放在一个固定的点上。这样产生的360度全景照片就可以定义成是一个包裹在球体二维表面上的投影。
360度全景照片在球体二维表面上的投影
Treating the panorama as a projection on a sphere with a rectilinear coordinate system is advantageous when dividing up the image into rectilinear tiles, and serving images based puted tile coordinates.
把全景图当成是在球体上的投影,并用一个直角坐标系来描述。当需要把图片分割成直角瓦片,并通过计算瓦片坐标提供相对应的图片时,这样做是很有好处的。
Creating Custom Panorama Tiles
Street View also supports different levels of image detail through the use of a zoom control, which allows you to zoom in and out from the default view. Generally, Street View provides five levels of zoom resolution for any given panorama image. If you were to rely on a single panorama image to serve all zoom levels, such an image would either necessarily be quite large and significantly slow down your application, or be of such poor re