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Orthorectifying RapidEye Data RPC and Rigorous Modeling

PCI Geomatics -

RapidEye is a constellation of five Earth observation satellites that was launched on August 29, 2008. RapidEye AG (www.rapideye.de), a German GeoSpatial Information provider, is the owner of this RapidEye satellite constellation. The five satellites are named TACHYS (Rapid), MATI (Eye), CHOMA (Earth), CHOROS (Space) and TROCHIA (Orbit). They are capable of producing 5m resolution imagery daily at any point on Earth.

RapidEye commercial satellites are the first to offer the Red-Edge band data. Data is collected in Blue, Green, Red, Red-Edge and Near Infrared bands. RapidEye data is mainly used for Agriculture, Forestry, Security and Emergency, Environment, Spatial Solutions and Energy & Infrastructure applications.

The following tutorial explains the capability of Geomatica OrthoEngine v10.2 to orthorectify RapidEye Basic Level 1B product.

Rational Polynomial Coefficients (RPC)
OrthoEngine is capable of performing Rational Functions based modeling using RapidEye Basic Product (Level 1B). Sub-pixel accuracy can be achieved in OrthoEngine for such RapidEye projects without GCPs. If required, an addition of 1-4 GCPs into a Rational Function project can further improve the accuracy of your final ortho image.


Initial Project Setup
Start OrthoEngine and click ‘New’ on the File menu to start a new project. Give your project a ‘Filename’, ‘Name’ and ‘Description’. Select ‘Optical Satellite Modeling’ as the Math Modeling Method. Under Options, select ‘Rational Function (Extract from Image)’ option. After accepting this panel you will be prompted to set up the projection information for the output files, the output pixel spacing, and the projection information of GCPs. Enter the appropriate projection information for your project.

 

Data Input
Select ‘Data Input’ option from ‘Processing Step’ drop down and click on ‘Open Image’ button. Use ‘New Image’ to point to the XML file in RapidEye Level 1B dataset.

At this stage OrthoEngine gives you an option to ‘Import Data to Pix file to Optimize Processing’. Click yes to import the raw L1B data into Geomatica .pix format and optimize further image processing. User can also click ‘No’ and the selected XML file will simply get listed in the Open Image box as an uncorrected Image.

 

GCP Collection
At this stage an ortho image can be generated directly in the absence of any GCPs. The model will be computed based on the supplied RPCs. If GCPs are available, they can be added into the project using GCP/TP Collection processing step. The model can be automatically computed (using Compute Model option), and GCPs can be reviewed through Residual report.

Ortho Generation
Proceed to the ‘Ortho Generation’ processing step and click on ‘Schedule Ortho Generation’. Select the file to be processed and select an appropriate DEM file. Set other processing options before generating the final ortho image.

 

The final RapidEye ortho image is generated in three easy steps using OrthoEngine’s Rational Function modeling.

 

Rigorous Modeling
RapidEye Rigorous modeling can also be performed on RapidEye Basic Product (Level 1B) in OrthoEngine. User needs to supply minimum of 6 accurate GCPs for performing the block adjustments.

Initial Project Setup
Start a new project and select the math modeling method as ‘Optical Satellite Modeling’. Under ‘Options’ select ‘Toutin’s Model’.

 

Data Input
You do not need to import RapidEye Basic Product (Level 1B) imagery into a PIX file using ‘Read from CD- ROM’ as this type of data is supported directly in the Generic Database Library (GDB). The image can be opened directly using the XML file in the GCP collection stage as shown in section 2.3


Collect GCPs and Tie Points
Select the ‘GCP/TP Collection’ processing step and click on ‘Collect GCPs Manually’ option. GCP collection panel with Open Image box will pop-up. Use ‘New Image’ button to point to the raw XML RapidEye data file. OrthoEngine will point user to import the file into PIX format at this stage for optimized processing. User can either import the file into Geomatica PIX format or simply add the uncorrected raw XML file in the project.

 

Click ‘Quick Open & Close’ and the image will be displayed into OE viewer. Now GCP collection can be done using various options: ‘Manual Entry’, ‘Geocoded Images/Vectors’, ‘Chip Database’ or a ‘Text File’.

For RapidEye Rigorous model, a minimum of six accurate GCPs per image (or more, depending on the accuracy of the GCPs and accuracy requirements of the project) are required. After collecting the GCPs, select the ‘Model Calculation’ Processing Step and click on ‘Compute Model’. Check ‘Residual Report’ panel (under the Reports processing step) to review the initial results.

 

Generating Orthos
The final step is to set up your Ortho Image Production. Proceed to the ‘Ortho Generation’ processing step and select the file(s) to be orthorectified. Choose the appropriate DEM file to be used in the processing and other processing parameters. Click on ‘Generate Orthos’ to create the final Orthorectified image.

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