RPC correction

RPC What is it? ？

RPC（rational polynomial coefficients）, Rational polynomial coefficients .RPC It is the fitting form of the strict geometric model of the sensor .
It is the platform track parameter measured according to the satellite platform load 、 Attitude parameters 、 Image of sensor installation parameters and sensor internal geometric parameters - Geometric model of earth relation ${}^{[1]}$.

RPC The calculation process

    P = (Latitude     - LAT_OFF)    / LAT_SCALE
    L = (Longitude    - LONG_OFF)   / LONG_SCALE
    H = (Height       - HEIGHT_OFF) / HEIGHT_SCALE
    rn = (Row         - LINE_OFF)   / LINE_SCALE
    cn = (Column      - SAMP_OFF)   / SAMP_SCALE

In style ,P、L、H Are the normalized longitude 、 Latitude and elevation . rn、cn They are normalized row and column numbers , The normalized value is used to reduce the error in the calculation process .

The relationship between the two is as follows ：

molecular 、 The denominator is three times 20 Polynomial function of terms .
among (LINE_NUM_COEF_n, LINE_DEN_COEF_n, SAMP_NUM_COEF_n, SAMP_DEN_COEF_n) They contain 20 A coefficient of , The functional relationship between numerator and denominator is as follows ：

In general ,GeoTIFF The file contains RPC Information , Domestic satellites also generally have .rpc or .rpb File to store RPC Information , This information contains 4 A polynomial 80 A coefficient of , as well as **_OFF,**_SCALE etc. 10 Parameters , Therefore, we only need to know the elevation data to solve the longitude and latitude of each pixel , Thus ortho correction can be realized .

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It should be noted that the reference coordinate systems of the longitude and latitude are WGS84 Coordinate system

be based on arcpy Of RPC correction

The article links

Reference material

[1] Liu Jiang , Yueqingxing , Qiuzhenge . RPC Research on calibration methods [J]. Remote sensing of land and resources , 2013.
[2] Li Deren , Zhang Guo , Jiangyonghua , etc. . Research on geometric accuracy of domestic optical satellite images [J]. Spacecraft engineering , 2016, 25(1):9.

Other information ：
RPCs in GeoTIFF