为什么 WorldView 3 的图像空间分辨率是这样的？
Why is the spatial resolution of image from WorldView 3 like this?
从gdalinfo 20141030-wv03.tif输出的这张图片是这样的：
Driver: GTiff/GeoTIFF
Files: 20141030-wv03.tif
Size is 16484, 15253
Coordinate System is:
GEOGCRS["WGS 84",
DATUM["World Geodetic System 1984",
ELLIPSOID["WGS 84",6378137,298.257223563,
LENGTHUNIT["metre",1]]],
PRIMEM["Greenwich",0,
ANGLEUNIT["degree",0.0174532925199433]],
CS[ellipsoidal,2],
AXIS["geodetic latitude (Lat)",north,
ORDER[1],
ANGLEUNIT["degree",0.0174532925199433]],
AXIS["geodetic longitude (Lon)",east,
ORDER[2],
ANGLEUNIT["degree",0.0174532925199433]],
ID["EPSG",4326]]
Data axis to CRS axis mapping: 2,1
Origin = (113.959353776485997,23.091020758099145)
Pixel Size = (0.000002966620901,-0.000002966620901)
Metadata:
AREA_OR_POINT=Area
DataType=Generic
Image Structure Metadata:
COMPRESSION=LZW
INTERLEAVE=PIXEL
Corner Coordinates:
Upper Left ( 113.9593538, 23.0910208) (113d57'33.67"E, 23d 5'27.67"N)
Lower Left ( 113.9593538, 23.0457709) (113d57'33.67"E, 23d 2'44.78"N)
Upper Right ( 114.0082556, 23.0910208) (114d 0'29.72"E, 23d 5'27.67"N)
Lower Right ( 114.0082556, 23.0457709) (114d 0'29.72"E, 23d 2'44.78"N)
Center ( 113.9838047, 23.0683958) (113d59' 1.70"E, 23d 4' 6.22"N)
Band 1 Block=128x128 Type=Byte, ColorInterp=Red
NoData Value=256
Band 2 Block=128x128 Type=Byte, ColorInterp=Green
NoData Value=256
Band 3 Block=128x128 Type=Byte, ColorInterp=Blue
NoData Value=256
空间分辨率为(0.000002966620901,-0.000002966620901)，这个值怎么理解？
我还检查了 WorldView 2 中的另一张图片，输出是：
Driver: GTiff/GeoTIFF
Files: 20150708.tif
Size is 9984, 10132
Coordinate System is:
PROJCRS["WGS 84 / UTM zone 50N",
BASEGEOGCRS["WGS 84",
DATUM["World Geodetic System 1984",
ELLIPSOID["WGS 84",6378137,298.257223563,
LENGTHUNIT["metre",1]]],
PRIMEM["Greenwich",0,
ANGLEUNIT["degree",0.0174532925199433]],
ID["EPSG",4326]],
CONVERSION["UTM zone 50N",
METHOD["Transverse Mercator",
ID["EPSG",9807]],
PARAMETER["Latitude of natural origin",0,
ANGLEUNIT["degree",0.0174532925199433],
ID["EPSG",8801]],
PARAMETER["Longitude of natural origin",117,
ANGLEUNIT["degree",0.0174532925199433],
ID["EPSG",8802]],
PARAMETER["Scale factor at natural origin",0.9996,
SCALEUNIT["unity",1],
ID["EPSG",8805]],
PARAMETER["False easting",500000,
LENGTHUNIT["metre",1],
ID["EPSG",8806]],
PARAMETER["False northing",0,
LENGTHUNIT["metre",1],
ID["EPSG",8807]]],
CS[Cartesian,2],
AXIS["(E)",east,
ORDER[1],
LENGTHUNIT["metre",1]],
AXIS["(N)",north,
ORDER[2],
LENGTHUNIT["metre",1]],
USAGE[
SCOPE["unknown"],
AREA["World - N hemisphere - 114°E to 120°E - by country"],
BBOX[0,114,84,120]],
ID["EPSG",32650]]
Data axis to CRS axis mapping: 1,2
Origin = (291153.100000000034925,2705938.760000000242144)
Pixel Size = (0.510000000000000,-0.510000000000000)
Metadata:
AREA_OR_POINT=Area
TIFFTAG_XRESOLUTION=1
TIFFTAG_YRESOLUTION=1
Image Structure Metadata:
INTERLEAVE=BAND
Corner Coordinates:
Upper Left ( 291153.100, 2705938.760) (114d56'22.85"E, 24d27'10.88"N)
Lower Left ( 291153.100, 2700771.440) (114d56'25.58"E, 24d24'22.98"N)
Upper Right ( 296244.940, 2705938.760) (114d59'23.60"E, 24d27'13.32"N)
Lower Right ( 296244.940, 2700771.440) (114d59'26.26"E, 24d24'25.41"N)
Center ( 293699.020, 2703355.100) (114d57'54.57"E, 24d25'48.15"N)
Band 1 Block=9984x1 Type=Byte, ColorInterp=Red
Band 2 Block=9984x1 Type=Byte, ColorInterp=Green
Band 3 Block=9984x1 Type=Byte, ColorInterp=Blue
空间分辨率为(0.510000000000000,-0.510000000000000)。我如何理解它们之间的区别？谢谢。
您的图像在两个不同的坐标系中。
您的第二个文件 20150708.tif 是 UTM 投影（准确地说是 UTM 50N），其地图单位以米为单位 - 这就是像素分辨率以米 (0.51m) 为单位的原因。
您的第一个文件 20141030-wv03.tif 使用广泛使用的地理坐标系 World Geodetic System 1984 (or WGS84) which has map units in degrees, giving you the pixel resolution also in (decimal) degrees. On the equator 0.00001 degrees is around 1.11 meters，因此两个图像可能具有相同的分辨率。
有关 WGS84 与 UTM 的更多信息，this post on GIS stackexchange 可能很有趣。
从gdalinfo 20141030-wv03.tif输出的这张图片是这样的：
Driver: GTiff/GeoTIFF
Files: 20141030-wv03.tif
Size is 16484, 15253
Coordinate System is:
GEOGCRS["WGS 84",
DATUM["World Geodetic System 1984",
ELLIPSOID["WGS 84",6378137,298.257223563,
LENGTHUNIT["metre",1]]],
PRIMEM["Greenwich",0,
ANGLEUNIT["degree",0.0174532925199433]],
CS[ellipsoidal,2],
AXIS["geodetic latitude (Lat)",north,
ORDER[1],
ANGLEUNIT["degree",0.0174532925199433]],
AXIS["geodetic longitude (Lon)",east,
ORDER[2],
ANGLEUNIT["degree",0.0174532925199433]],
ID["EPSG",4326]]
Data axis to CRS axis mapping: 2,1
Origin = (113.959353776485997,23.091020758099145)
Pixel Size = (0.000002966620901,-0.000002966620901)
Metadata:
AREA_OR_POINT=Area
DataType=Generic
Image Structure Metadata:
COMPRESSION=LZW
INTERLEAVE=PIXEL
Corner Coordinates:
Upper Left ( 113.9593538, 23.0910208) (113d57'33.67"E, 23d 5'27.67"N)
Lower Left ( 113.9593538, 23.0457709) (113d57'33.67"E, 23d 2'44.78"N)
Upper Right ( 114.0082556, 23.0910208) (114d 0'29.72"E, 23d 5'27.67"N)
Lower Right ( 114.0082556, 23.0457709) (114d 0'29.72"E, 23d 2'44.78"N)
Center ( 113.9838047, 23.0683958) (113d59' 1.70"E, 23d 4' 6.22"N)
Band 1 Block=128x128 Type=Byte, ColorInterp=Red
NoData Value=256
Band 2 Block=128x128 Type=Byte, ColorInterp=Green
NoData Value=256
Band 3 Block=128x128 Type=Byte, ColorInterp=Blue
NoData Value=256
空间分辨率为(0.000002966620901,-0.000002966620901)，这个值怎么理解？
我还检查了 WorldView 2 中的另一张图片，输出是：
Driver: GTiff/GeoTIFF
Files: 20150708.tif
Size is 9984, 10132
Coordinate System is:
PROJCRS["WGS 84 / UTM zone 50N",
BASEGEOGCRS["WGS 84",
DATUM["World Geodetic System 1984",
ELLIPSOID["WGS 84",6378137,298.257223563,
LENGTHUNIT["metre",1]]],
PRIMEM["Greenwich",0,
ANGLEUNIT["degree",0.0174532925199433]],
ID["EPSG",4326]],
CONVERSION["UTM zone 50N",
METHOD["Transverse Mercator",
ID["EPSG",9807]],
PARAMETER["Latitude of natural origin",0,
ANGLEUNIT["degree",0.0174532925199433],
ID["EPSG",8801]],
PARAMETER["Longitude of natural origin",117,
ANGLEUNIT["degree",0.0174532925199433],
ID["EPSG",8802]],
PARAMETER["Scale factor at natural origin",0.9996,
SCALEUNIT["unity",1],
ID["EPSG",8805]],
PARAMETER["False easting",500000,
LENGTHUNIT["metre",1],
ID["EPSG",8806]],
PARAMETER["False northing",0,
LENGTHUNIT["metre",1],
ID["EPSG",8807]]],
CS[Cartesian,2],
AXIS["(E)",east,
ORDER[1],
LENGTHUNIT["metre",1]],
AXIS["(N)",north,
ORDER[2],
LENGTHUNIT["metre",1]],
USAGE[
SCOPE["unknown"],
AREA["World - N hemisphere - 114°E to 120°E - by country"],
BBOX[0,114,84,120]],
ID["EPSG",32650]]
Data axis to CRS axis mapping: 1,2
Origin = (291153.100000000034925,2705938.760000000242144)
Pixel Size = (0.510000000000000,-0.510000000000000)
Metadata:
AREA_OR_POINT=Area
TIFFTAG_XRESOLUTION=1
TIFFTAG_YRESOLUTION=1
Image Structure Metadata:
INTERLEAVE=BAND
Corner Coordinates:
Upper Left ( 291153.100, 2705938.760) (114d56'22.85"E, 24d27'10.88"N)
Lower Left ( 291153.100, 2700771.440) (114d56'25.58"E, 24d24'22.98"N)
Upper Right ( 296244.940, 2705938.760) (114d59'23.60"E, 24d27'13.32"N)
Lower Right ( 296244.940, 2700771.440) (114d59'26.26"E, 24d24'25.41"N)
Center ( 293699.020, 2703355.100) (114d57'54.57"E, 24d25'48.15"N)
Band 1 Block=9984x1 Type=Byte, ColorInterp=Red
Band 2 Block=9984x1 Type=Byte, ColorInterp=Green
Band 3 Block=9984x1 Type=Byte, ColorInterp=Blue
空间分辨率为(0.510000000000000,-0.510000000000000)。我如何理解它们之间的区别？谢谢。
您的图像在两个不同的坐标系中。
您的第二个文件 20150708.tif 是 UTM 投影（准确地说是 UTM 50N），其地图单位以米为单位 - 这就是像素分辨率以米 (0.51m) 为单位的原因。
您的第一个文件 20141030-wv03.tif 使用广泛使用的地理坐标系 World Geodetic System 1984 (or WGS84) which has map units in degrees, giving you the pixel resolution also in (decimal) degrees. On the equator 0.00001 degrees is around 1.11 meters，因此两个图像可能具有相同的分辨率。
有关 WGS84 与 UTM 的更多信息，this post on GIS stackexchange 可能很有趣。