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IMAGINE
OrthoBASE
Reviewed by: Mike Renslow, Paul Stupey, & Todd Brochu
(reprinted from PE&RS May 2000)
Product
Information
Vendor: ERDAS, Inc.Release Date: May 1999 Requirements Software: Hardware: Recommended Configuration: Cost: |
Summary IMAGINE OrthoBASE is an extension to the ERDAS IMAGINE software package for the generation of digital orthoimagery. The operator begins orthophoto production utilizing accepted methodologies for ortho-rectification (orientation parameters, control, tie point collection, mensuration, block adjustment, DEM application, and rectification), and has the image processing tools of ERDAS IMAGINE to finish the products. A series of menus, workflows, and wizards are in place to guide the operator and verify that each rectification step is completed. A linear table wizard for each project uses a ‘red’ (not completed) and ‘green’ (completed) color coding process driving the operator to complete each step in the proper order, and assures that each requirement is satisfied. Features Supported Imagery Formats: IMAGINE OrthoBASE can directly read and input a wide variety of imagery sources (same as ERDAS IMAGINE ) and types of imagery: aerial, satellite, video, 35 mm, and digital CCD cameras. IMAGINE OrthoBASE has the functionality to estimate camera parameters when they are not available. Model Definition: For our review using standard aerial photographs, we measured the fiducial marks which the software generated using a semi-automated interior orientation approach. It was useful to have the project’s ‘block file’ containing all the pertinent information in one place, i.e., map projection, camera type, film dimensions, orientation parameters, photos, etc. Another useful functionality is that the map and projection information associated with an image may be deleted using the “Delete Map Model” command, and edited using different parameters. Ground Control Points can be visually displayed over their relevant locations as a ‘new scan’ which we found to be useful if the scan contains pre-drilled points from the diapositives, or if the area has been pre-marked with targets. IMAGINE OrthoBASE is configured to accept ‘control’ from a variety of other sources, such as, existing orthophotos, vector data, and ASCII formatted survey reports. The control GUI displays the active imagery with zooming functionality and image enhancement capability. All of the GCP values are displayed on screen. With the imagery installed on the workstation’s hard drive, this process went relatively fast as the software allows for quick image roaming and continuous zooming. IMAGINE OrthoBASE creates an ‘image pyramid’ with multiple resolutions for quick screen refresh. A large format monitor is very useful during these initial setup steps. The GUI simultaneously opens several windows within one interface, thereby providing an efficient production flow for the collection of ground control points. Automatic Tie Point Selection: IMAGINE OrthoBASE can automatically select tie points between multiple strips of imagery. The user can specify the “Intended Number of Tie Points Per Image” up to 500 with an option to select points or keep all of the points. The GUI of the automated tie point function displays a ‘point generation’ properties dialog allowing the user to select a variety of options and the intended number of tie points per image. The options include the search size, correlation size, least squares size, feature point density, coefficient limit, and initial accuracy. Aerotriangulation/Bundle Adjustment: IMAGINE OrthoBASE performs the aerotriangulation and a self-calibrated bundle adjustment. Automatic error checking identifies probable errors in the AT data; the photogrammetrist should review these residuals and evaluate/correct/adjust the solution as required before proceeding. Statistical weights can be assigned to the x and y image coordinates representing the image position quality for GCPs, checkpoints, and tie points. DEM For Rectification: For our review we utilized a previously generated DEM available from archive. The GUI accepts a variety of CAD formats and gridded data sources including USGS DEMs. At the time of our initial review, .dgn (Intergraph design file) format was not listed, however, when called upon for assistance, ERDAS provided a work-around (see comments about customer support). The documentation discusses the development of a DEM from stereo image auto-correlation or ‘create surface’ routine, however we did not review this function. Orthophoto Production is completed by selecting controlled
imagery and the DEM, and executing the rectification command
windows. A batch mode is available. Quality Control Verification is contained at every step of the project setup to orthophoto rectification, as already mentioned. IMAGINE OrthoBASE contains two error or blunder checking models which identify any errors as the user works through each step. The operator analyzes the resulting data and determines that the data are within the parameters of the specified accuracy. As each function is completed leading to the final rectification, the error budget is displayed in a data evaluation dialog box. Documentation consists of two volumes: a ‘User’s Guide’ and a ‘Tour Guide’ (a Reference Document). We found both documents to be useful: the User’s Guide allows the experienced user to follow the process leading directly to rectification; the Tour Guide contains a wealth of pointers and background to the novice user. The trouble-shooting tips at the end of each section were very useful. Customer Service proved to be quite satisfactory. During the course of our review, our questions were answered quickly “on-line” and through personal communications. We requested a work-around for integrating .dgn files in IMAGINE OrthoBASE and received a well-constructed dialogue with graphic clips describing each step. Conclusions Reviewed by: |