Overwatch RemoteView Pro RPC Metadata Processing … · The Information contained herein is not...

ImStrat Corporation

Overwatch RemoteView Pro RPC Metadata Processing Problem By Kevin B. Crichlow

ImStrat Corporation Technical Report

Suite 100, 20 Bennett Street Carleton Place, Ontario

K7C-4J9 Canada April 2010

RemoteView Pro RPC Metadata Processing Problem

ImStrat Corporation 2

Foreword

The Information contained herein is not intended as a criticism of the software, but is intended to highlight a problem experienced by the users of various versions here at ImStrat Corporation.

It aims to bring to bear the collective resources of the photogrammetric experts at Overwatch Geospatial of Virginia, the imaging scientists at Digital Globe and ImStrat Corporation to the problem’s center of gravity in the hopes that a speedy solution can be found.



Abstract

This document contains a description of the RPC metadata processing issues encountered here at ImStrat Corporation within RemoteView Pro 3.0.7 environment.

My test scenario consisted of a 20 February 2010 WorldView-2 panchromatic image of Beirut in conjunction with 90m SRTM elevation data from the CGIAR website and was performed on a Windows XP Pro machine.

The tests show the non-transference of RPC data from the original satellite image to the GeoTIFF and NITF image chip and the impact upon standard operations such as GeoJump.

Finally, I give my suggestion for a solution to the problem.



Table of Contents

Abstract ______________________________________________________________ 3

The RPC Value Problem ________________________________________________ 5 Problem Definition _____________________________________________ 5 Functionality that stops working___________________________________ 5 Technical References __________________________________________ 6

RPC Problem Example__________________________________________________ 7 Original Image ________________________________________________ 7 Test Bed Details_______________________________________________ 8

Original Image Metadata – RPC Data Present _______________________________ 9

GeoTIFF Metadata – RPC Data Not Present _______________________________ 10

GeoTIFF & NITF Image Chip - Errors ___________________________________ 11 GeoTIFF Image Chip – CE & LE Error ____________________________ 11 GeoTIFF Image Chip – GeoJump Error____________________________ 12 NITF Image Chips – Export Options Discrepancy ____________________ 13 Reference __________________________________________________ 14 NITF Metadata Error – RPC Information Absent _____________________ 15 Reference __________________________________________________ 16

Suggested Solution ____________________________________________________ 17



The RPC Value Problem

Problem Definition The fundamental problem being faced by our RemoteView Pro users at present (This includes all versions from 2.8 – 3.07) is the NON TRANSFER of RPC information from the original Digital Globe satellite images into an Image Chip. NOTE:

This problem may not be solely be restricted to Digital Globe products but may extend to other satellite vendors as well.

It is our understanding that RemoteView Pro requires the presence of the ERR_RAND & ERR_BIAS values as well as the RPC Coefficient values contained within either the image metadata file or the associated text file in conjunction with ELEVATION data of the said AOI. The LACK of the following critical RPC values causes several RemoteView Pro operations to GIVE ERROR MESSAGES or NOT WORK at all : -

ERR_RAND & ERR_BIAS values RPC coefficient values lineOffset and sampOffset values that are automatically modified by

the software to take into account the fact that that the image is now a CHIP of the original.

Functionality that stops working 1) The ability to use the Geomarker tool to mark the geolocation of a said object of interest within the satellite image CHIP. 2) The ability to use the Geomarker Tool or the PQA tool to display CE and LE values for chosen points of interest. This will enable the analyst to also drag and drop this information to annotate the image as necessary 3) RVPinPoint for precise geolocation and Targeting 4) The ability to use the MENSURATION TOOLKIT to make precise measurements of features within the image chip.



Technical References White papers by Gene Rose

Basic Photogrammetry in RV Multi-Image Geolocation & 3D Feature Extraction



RPC Problem Example

Original Image

NOTE: The Boxed area around the terminal represents the area that was CHIPPED with Upper Left X & Y Position highlighted. The accompanying text files in the GeoTIFF chip folder and NITF chip folder refer to this image chip.



Test Bed Details Windows XP Pro RemoteView Pro: Version 3.0.7 WorldView-2 Panchromatic 50cm Satellite Image SRTM_44_06 (http://srtm.csi.cgiar.org/ (90m)

Please contact me at [email protected] for scene ID details in the event you wish to perform tests using the same dataset



Original Image Metadata – RPC Data Present



GeoTIFF Metadata – RPC Data Not Present



GeoTIFF & NITF Image Chip - Errors

GeoTIFF Image Chip – CE & LE Error

CE & LE ERROR Please NOTE the LACK of CE & LE information, this despite the fact that that option remains checked on

Elev: SRTM 90m http://srtm.csi.cgiar.org



GeoTIFF Image Chip – GeoJump Error

GEOJUMP ERROR When I tried to GeoJump to the GeoTIFF/NITF Chip, I got the error message on the left displayed on the screen

Comment

It is unclear as to whether this is caused by one of the following: -

The huge CE error that accompanies the SRTM elevation data alone

The huge CE error due to inaccurate SRTM elevation data and the lack of RPC values

If the lack of RPC values is the sole contributing factor.

Note

For more information on how RemoteView Pro uses the ERR_RAND & ERR_BIAS RPC Values please see the white paper by Gene Rose entitled “Basic Photogrammetry in RV”



NITF Image Chips – Export Options Discrepancy

Comment 1

The NITF 2.1 image chip was made according to the instructions in the help file. The Copy Target information box was checked BUT the checkbox for Compute New RPCs is conspicuously absent as compared to the screenshot contained within the help file of 3.0.7.



Comment 2

Currently the only way to access the “Compute New RPC” checkbox is to re-save the new NITF 2.1 chip as an NITF 2.1 image a second time. When you click on the “Format Options” button, the “Compute New RPC” checkbox will be available.

I was advised NOT to “Compute New RPCs” by the Overwatch Technical Authority, as they stated that this should only be done if georeferencing information within the image was changed using the image calibration tools.

As you can see in the screenshot, the NITF2_1 Export options have been made the same as the NITF2_0 Export Options in the help file.

Comment 3

You can also access the “Compute New RPC” checkbox on the first try, if you re-save an original Digital Globe image as an NITF2_1 image (i.e. the entire image).

Reference Chipping & Exporting section of the RV User Manual



NITF Metadata Error – RPC Information Absent



Reference Please see the Metadata text files that accompany this report for reference.



Suggested Solution

The coding of a module that enables the automatic re-calibration of the lineOffset and sampOffset values in the RPC metadata file to adjust for the new “Upper Left hand corner” position of new image chip as well as ensuring that the ERR_RAND and ERR_BIAS values are populated.

This functionality would be implemented in the Format Options section of Save as GeoTIFF and NITF 2.0 / 2.1 options.

For further information or questions please contact me at anytime

Sincerely,

_____________________

Kevin B. Crichlow

Geomatics Technical Support

[email protected]

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