Tips and Tutorials \ Update PLEIADES image RPCs
This tutorials shows how to update a Pleiades image's RPCs from an external refined model
Type: Tip
Overview
RPCs (for Rational Polynomial Coefficients) are generic description of the rigorous sensor models allowing to compute ground-to-image transformation with rational polynomial functions .The rational function polynomial equation numerators and denominators each are 20-term cubic polynomial functions.
In the AI4GEO project, the IGN provides refined models that cannot be used with the OTB unless updating the RPCs. This tutorial presents the steps to perform this update.
Warning : this tutorial is only relevant for CNES/IGN agents. It is based on the Euclidium tool which is property of CNES/IGN/Magelium.
Simple RPC extraction
cd /work/OT/ai4geo/SOFT/CNES_IGN
source init.sh
simple_rpc_extraction -i <input_folder> <output_path/RPC_X>.xml
Usage
First, make sure to be a member of the eolab and ai4geo groups. if not, ask for nominative access to the folder.
1 - Go into the folder :
cd /work/OT/ai4geo/SOFT/CNES_IGN
2 - Source the initialization script :
source init.sh
3 - Launch the tool :
simple_rpc_extraction -i <input_folder> <output_path/RPC_X>.xml
You have to replace input_folder with the folder containing input images (typically, a folder with files such as .tif, DIMAP etc.), and replace the X in the output filename with the name of the input image. Doing this, the OTB will be able to read the this RPC file.
Example :
simple_rpc_extraction -i /work/OT/ai4geo/DATA/SENSOR/PHR/SRP_refined/PARIS_20180326_T/CP/IMG_PHR1A_P_001/ -o RPC_PHR1A_P_201803261058346_SEN_5545308101-1.XML
Once the updated RPC file has been generated, place it into the image folder in order to allow the OTB to read it. With our previous example, this gives :
mv RPC_PHR1A_P_201803261058346_SEN_5545308101-1.XML /work/OT/ai4geo/DATA/SENSOR/PHR/SRP_refined/PARIS_20180326_T/CP/IMG_PHR1A_P_001/
(In the case of AI4GEO you first have to get the DIMAP in folder /work/OT/ai4geo/DATA/SENSOR/PHR/SRP_refined/PARIS_20180326_T/MODELES/AFFINES, place it into the image folder and rename it into DIM_X.xml before launching the script)
Troubleshooting
If you cannot acess the folder, you are probably not in the right user group. Use the command groups to check if you are in ai4geo and eolab.
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