[Gdal-dev] adding gcp's

以下连续4封邮件说明了gdal中如何添加gcp，如何利用gcp，以及如何通过gdalwarp将gcp表示的参考关系转换为用tfw等表的仿射关系。并且GDAL的文档中有一段说明了gcp和仿射转换的关系：

The GDAL库 data model does not imply a transformation mechanism that must be generated from the GCPs ... this is left to the application. However 1st to 5th order polynomials are common.

Normally a dataset will contain either an affine geotransform, GCPs or neither. It is uncommon to have both, and it is undefined which is authoritative.

按照李林的翻译是：GDAL数据模型没有实现由GCPs...产生坐标系的变化的机制，而是把它留给实际应用。但是1到5阶多项式是通常使用的方法。通常一个数据集会包含仿射地理变换。和GCPS中的一个或者两个都没有。两个都有很少见。而且无法用权威坐标系定义。

这说明gdalwarp可以根据gcp点来生成仿射关系，从而达到简单的旋转拉伸几何纠正的目的，但是纠正的机制仅限于多项式的方式。

 

[Gdal-dev] adding gcp's

[Gdal-dev] adding gcp's

Bart van den Eijnden BEN at Syncera-ITSolutions.NL
Tue Aug 23 11:26:17 EDT 2005

• Previous message: [Gdal-dev] A silly question?
• Next message: [Gdal-dev] adding gcp's
• Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

---

Hi list,





I am trying to create a geotiff and add ground control points to it, using the following command:





gdal_translate ondergrond.tif ondergrond_new.tif -gcp 0 0 63978 458335 -gcp 1290 1619 85630 438699





When I do gdalinfo, the gcp's are added, but the corner info is not using it:





D:\ms4w\apps\stragisweb\htdocs\sites\westland\data\basis\geo>gdalinfo ondergrond_new.tif


Driver: GTiff/GeoTIFF


Size is 1290, 1169


Coordinate System is `'


GCP Projection =


GCP[  0]: Id=1, Info=


(0,0) -> (63978,458335,0)


GCP[  1]: Id=2, Info=


(1290,1619) -> (85630,438699,0)


Metadata:


TIFFTAG_SOFTWARE=IrfanView


TIFFTAG_XRESOLUTION=150


TIFFTAG_YRESOLUTION=150


TIFFTAG_RESOLUTIONUNIT=2 (pixels/inch)


Corner Coordinates:


Upper Left  (    0.0,    0.0)


Lower Left  (    0.0, 1169.0)


Upper Right ( 1290.0,    0.0)


Lower Right ( 1290.0, 1169.0)


Center      (  645.0,  584.5)


Band 1 Block=1290x6 Type=Byte, ColorInterp=Red


Band 2 Block=1290x6 Type=Byte, ColorInterp=Green


Band 3 Block=1290x6 Type=Byte, ColorInterp=Blue





What am I doing wrong?





Thanks in advance.





Best regards,


Bart





Bart van den Eijnden


Syncera IT Solutions


Postbus 270


2600 AG  DELFT





tel.nr.: 015-7512436


email: BEN at Syncera-ITSolutions.nl

---

• Previous message: [Gdal-dev] A silly question?
• Next message: [Gdal-dev] adding gcp's
• Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

---

More information about the Gdal-dev mailing list