Vr Mapping

VrTwo Orientation is used to create stereo image pairs (or models) for viewing in the VrTwo and VrLite mapping software. Stereo models may be generated manually or by importing the results from various aerial triangulation programs. Orientations may be performed on a single model or multiple models may be oriented in a batch mode. The importing of models from aerial triangulation may be performed from the exterior orientations or from the measurements used to tie images and strips together.

VrTwo Orientation Basics

VrTwo Orientation will start by opening the Main Window.

Starting an Application (Command)

Pulling down a menu and selecting an item may start commands. Commands may also be started from a key-in using the command name. Each command name is the first three letters of the first two words on the pull down. For example: The command name for Open Project is OpePro. If this rule is not followed the key-in is listed after the command in parenthesis.

The Main Window

The Main Window in Image Utility contains the command pull down menus, a key-in area, two information areas, a progress bar and the coordinate display. Commands names may be typed into the key-in area at almost any time. On the border of the Main Window is shown the active project name.

Using VrTwo Orientation

VrTwo Orientation’s main purpose is to create stereo models containing left and right image pairs that can be used by VrTwo. These models consist of left and right epipolar images and an orientation parameter file. The parameter file has the extension of .orp, and contains the orientation parameters required for VrTwo to work with stereo images. VrTwo Orientation is project based, and requires a project to be created before any processing can be done. A project in VrTwo Orientation contains a list of images, camera files, and model definitions. Each project in VrTwo Orientation is divided into models. Each model contains one left image and one right image, resulting in a stereo image pair.

The following files are needed to set a stereo model.

Images with overlap suitable for stereo viewing. This overlap is normally 60%.
A camera calibration. This will be used to create a Vr Mapping camera (.cam) file
A ground coordinate file.
An exterior orientation or measurement file from aerial triangulation if importing orientations.

Following is a typical workflow for VrTwo orientations.

1. Create the camera calibration (.cam) file

2. Create the VrTwo orientation project

3. Create or import interior orientations

4. Perform relative and absolute orientations manually, or import them from aerial triangulation exterior orientations or image measurements.

The Vr Image Utility program may be used to prepare the images for the project by attaching the strip location, image pixel size and camera to each image. It can also be used to perform automatic interior orientations. The VrTwo orientation program can also be used to set up the images for the project. If several programs such as VrTwo Orientation, Vr Orthophoto or Vr Aerial Triangulation will use the same images then Vr Image Utility should be used to set up the images so the other programs may import the project file.

Command Reference

File

Preferences (Pre)

Preferences are used to set operating parameters for the VrTwo Orientation Program.

Use default directory? – Defines the usage of the default directory. The default directory is used as the start directory for items such as dialog boxes in which files may be selected. This value may be set to Yes or No.

Default directory – Defines the default directory which will be used if “Use default directory” is set to Yes.

Zoom scale factor (buttons 3,4) – Several of the orientations such as Relative Orientation allow zooming in and out on the images. This parameter is the scale factor that will be used when zooming in with button #4 (Mouse center button) and zooming out with button #4.

Image parameter file (.vim) location – Each image used in the VrTwo orientation program has an associated parameter (.vim) file. This file contains the interior orientation values and other image parameters. The image parameter file has the same name as the image but with a .vim file extension. These parameter files may be stored in the same directory (folder) as the images or they may be stored in the project folder. The two options for this value are Image Folder and Project Folder.

Show point labels in Relative and Absolute? – When making observations in relative and absolute orientations point labels that show the point sequence number follow the measuring mark. These labels may be turned off if needed. Some graphics cards a slow when updating these labels and turning off the labels is necessary.

Use stereo in View Relative Orientation 3D – When using the view relative orientation 3D function from the Orientation pull-down it is possible to view the model configuration in true 3D. This is possible if the computer has the necessary 3D hardware.

Offset Increment in View Relative Orientation 3D – The view relative orientation 3D function allows the interactive placement of the model view point offsets. This parameter is used as the increment when adjusting the offsets.

Scale Increment in View Relative Orientation 3D – The view relative orientation 3D function allows the interactive modification of the image size scale factors. This parameter is used as the increment when adjusting these scale factors.

Exit (Exi)

Exits VrTwo Orientation.

Camera

The camera menu is used to create, edit and import camera calibration parameters.

New Camera (NewCam)

The New Camera allows the user to create and edit a new camera calibration file. The user will be prompted for the file name for the new camera. Camera files in Vr Mapping have the .cam file name extension. See Edit Camera below for information on editing a camera file.

Edit Camera (EdiCam)

Edit Camera allows the user to edit an existing camera calibration file. The camera edited does not need to be one of the current cameras and any existing camera file may be edited. When edit camera is started the user will be prompted for a camera file name and when exiting the user will have the opportunity to save the modified camera calibration parameters.

Description – A text entry that describes the camera for user reference may be entered in this field. This description is for user reference only and is not used in model orientation.

Fiducial units – The units of the coordinate positions may be one of several different units which include millimeters, inches or pixels. Many of the programs that are used to calibrate handheld cameras output the focal length of the camera in pixels. The coordinates entered in to represent the fiducial positions must be the same units specified here.

Focal length – The distance from the camera focal point to the center of the lens is the focal length of the lens. This value is provided by the camera calibration report and is entered as the same units as the Fiducial units.

Photo size X Y – The size dimensions of the images are specified with these two parameter values. The size entered must be in the same units as the Fiducial units.

Calib principal point X Y – The calibrated principal point (also known as the point of best symmetry) is the point whose position is determined as a result of the camera calibration and is available from the camera calibration report. This coordinate position must be entered as the same units as the Fiducial units.

Fiducial X Y – The coordinate positions for up to eight fiducials may be entered and must be in the same units as the Fiducial units. Most aerial cameras have eight fiducials and it is strongly recommended that all eight be entered and used when computing interior orientation. When using only four fiducials errors may occur and not shown in the residuals if the wrong camera calibration is selected.

Edit Radial Distortions –

Lens distortion causes imaged positions to be displaced from the ideal or true locations. In aerial cameras these distortions are normally minimal but can still have an effect on accuracy. Some of the digital cameras have large lens distortions and radial distortions must be entered for accurate mapping results.

Adjustment mode – There are two methods of representing radial distortions which are by distance or with polynomial values. Most camera calibration programs output radial distortions values as polynomial parameters. Note that Angular parameters are listed as an option as one of the adjustment modes but this method is currently unsupported.

Distance Parameters – Radial distortions that are represented as concentric rings about the camera lens calibrated principal point may be entered as distance parameters. The radial distortions shown below are from a small format camera and show high radial distortion values.

Radial distance increment – This value represents the distance between the concentric rings that make up the distance parameters. This value is entered in as the same units as the Fiducial units.

Distortion value n – The distortion values for each distance are entered in these parameter values. There may be up to 15 values and they are entered as the same units as the Fiducial units.

Angular Parameters – The computation of radial distortions by angular parameters is currently unsupported. Please use distance or polynomial parameters

Polynomial Parameters – The polynomial values and principal point or autocollimination are provided by the camera calibration report. The mathematical model used is based on the Simultaneous Multi-camera Analytical Calibration (SMAC) method. Care should be taken when entering these parameters as entry errors will cause model orientation errors and distortions and will affect model accuracy.

Entry of Exponential Notation

The k0-k4 values and the p1-p4 values are entered into the Polynomial Parameters dialog box in exponential notation. The values entered from the USGS camera calibration report may have the decimal place moved one position to the left depending on the number entered. For example:

USGS value: 0.1403x10-3

Value typed: .1403e-3

Shown value: 1.403000e-004

K0-K4 – Up to five K coefficient values may be entered. These are coefficients of symmetric radial lens distortion from the camera calibration report. These values are entered in exponent form.

P1-P4 – Up to four P coefficient values may be entered. These are the coefficients of decentering distortion fro the camera calibration report. These values are entered in exponent form.

PPA X Y – The principal point of autocollimation is provided from the camera calibration report.

Import Camera

ISAT (CamIsa) – Imports camera calibrations from an ISAT file. The ISAT file can contain several camera definitions.

ISAT camera file – The ISAT camera file is defined in this field and this file name is normally “camera”.

Coordinates

The Coordinates menu provides functions to create and edit coordinate files. Please refer to Vr Mapping Coordinate File Format for information on the format and layout of the coordinate files used in VrTwo Orientation.

New Coordinate File (NewCoo)

A new coordinate file may be created with this command. The Format, State Plane Zone, Datum, UTM Zone and Units in the Edit Header dialog box are for user reference and are currently unused by the software. The user is prompted for a coordinate file name and then can enter the coordinate file parameters as follows:

Layout – The layout specifies the fields to place in the coordinate file and their order. Options are:

Name X Y Z Cx Cy, Cz

Name Y X Z Cy Cx, Cz

X Y Z Name Cx Cy, Cz

Y X Z Name Cy Cx, Cz

Name X Y Z

Name Y X Z

X Y Z Name

Y X Z Name

X Y Name

Y X Name

Where:

Name – Point name

X Y Z – Coordinates

Cx Cy Cz – X Y Z point weights

Format – Coodrinate formats include state plane, UTM (Universal Transverse Mercator) and Geographic.

State Plane Zone – Each state plane zone has a code and this code may be entered in this field.

Datum – Coordinate datum which includes two NAD (North American Datum) zones which are NAD 1927 or NAD 1983. The U.S. State Plane Zones (NAD 1983) represents the State Plane Coordinate System (SPCS) Zones for the 1983 North American Datum within United States. U.S. State Plane Zones (NAD 1983) is generalized and an approximation of the actual State Plane Coordinate System zone boundaries for the 1983 North American Datum. It is intended for visual reference at small and medium map scales.

UTM Zone – If the format is set to UTM the UTM (Universal Transverse Mercator) zone code may be entered in this field. There are 60 longitudinal projection zones that cover the earth’s surface numbered 1 to 60 starting at 180°W. Each of these zones is 6 degrees wide, apart from a few exceptions around Norway and Svalbard. A definition of the Universal Transverse Mercator coordinate system can be found at http://en.wikipedia.org/wiki/Universal_Transverse_Mercator_coordinate_system.

Units – Units specify the coordinate units that make up xyz coordinates in the file. The possible coordinate units are; US Foot, International Foot, Meters, Inches or Pixels.

Edit Coordinate File (EdiCoo)

Coordinates in an existing coordinate file may be edited using this command. The editing options include Add, Change and Delete. When this command is started the user can open any coordinate (.cor) file and the edited file may be saved when exiting the command.

Sort – Sorts the coordinate file based on the point name.

Search – Searches for a coordinate point by name. If the point name being searched for is found it will become the current point.

Edit Header – Allows the editing of the coordinate file header. (See the Edit Header in New Coordinate File).

Name – The point name may be alpha numeric and may be up to 32 characters in length.

X Y Z – The coordinate values for the point.

CX CY CZ – Point weights. These may be used in the coordinate file depending on the File Layout (see New Coordinate File). Normally point weights are expressed in ground units.

Add – The current point will be added to the coordinate file

Change – The current point will be updated with the current Name, X, Y, Z, CX, CY and CZ values.

Delete – The current point will be deleted.

Null Axis Value (NullAxi)

When defining coordinates it is possible to have points in which all three axis are not defined. In the case of a vertical only point the x and y values are not used and in the case of a horizontal only point the z is not used. The Null Axis Value defines the value that will indicate that an axis does not have a coordinate value. This value is typically zero but in cases where zero is a valid coordinate value in the map data a value such as -999 should be used.

Project

The Project menu is used to manage VrTwo Orientation projects and has the ability to create, open, save, edit and delete projects. Change Drive allows projects to be moved between different drives and folders. The Vr Two Orientation project file name has a .vpr file name extension.

New Project (NewPro)

Creates a new project and allows starts Edit Project.

Open Project (OpePro)

Opens an existing project. It is not necessary to close the current project before opening another. All current project parameters will be saved automatically before another is opened.

Save Project As (SavPro)

Saves the current project with a different file name

Edit Project (EdiPro)

Allows editing of the current project.

Project name – This field displays the current project file. This file was created when the project was created in Project -> New Project. The field is for display only and cannot be modified.

Coordinates – The project ground coordinate file may be set in this field by pressing the […] button at the end of the field. When importing orientations from aerial triangulation this file should contain the coordinates for the pass, tie and ground control points. A coordinate file of this type is always produced from an aerial triangulation adjustment.

Photo overlap – This field defines the approximate photo forward overlap and is expressed as a percentage. Typical aerial mapping jobs use 60% photo overlap.

Model directory – The model orientation process produces parameter and image files needed for the display of stereo. The Model Directory field defines the target directory (folder) in which these files will be placed. The files placed in the directory are the epipolar images, the orientation parameter (.orp) files and the model definition (.vmo) files. Leaving this field blank will place these files in the project directory.

Images – The Images area of the dialog box contains a display list of the images that are currently in the project, the “Define Images” and “Import Image Util” buttons.

Define Images – Pressing this button will start the “Define Images” dialog (see below).

Import Image Util – If images have been previously defined in the Vr Image Utility program these parameters may be transferred to this program by pressing this button. This will avoid re-entering these parameters. The Vr Image Utility project file has a file name extension of .iup.

Models – The Models area of the dialog box contains a display of the currently defined models with the model parameters and the Add Model, Remove Model, Report and Add Models buttons. The active model’s name is highlighted in the list of models and any model may become active by clicking its model name.

Left image – The left image name for the current model is displayed in this field and by be changed by clicking on the field and selecting a new image from the list.

Right image – The right image name for the current model is displayed in this field and by be changed by clicking on the field and selecting a new image from the list.

Resample mode – There are three modes available when re-sampling images to create epipolar images which include Nearest Neighbor, Bilinear and Bicubic. These re-sampling modes affect the quality of the output image and the time it takes to create the epipolar images as follows:

· Nearest Neighbor - Fastest re-sampling time, lower quality. High contrast edges will appear more jagged using this mode

· Bilinear – Medium re-sampling time, medium image quality. The image quality is softer than nearest neighbor and is normally acceptable for stereo viewing.

· Bicubic – Highest re-sampling time, highest image quality. The image quality is the softest of the three methods. Bicubic re-sampling is commonly used when creating orthophotos.

Image resolution – This field specifies the resolution of the epipolar images and is expressed in millimeters. For example; 12 microns would be entered as 0.012 millimeters. The resolution of the epipolar images do not need to be the same as the original image although using the same resolution is recommended. In cases when the debugging of a stereo model orientation and re-sampling is done multiple times while testing orientation parameters, it is useful to re-sample at a higher resolution such as 30 microns (0.030 millimeters) to obtain a stereo model quickly. “Over sampling” is a process to using a higher image resolution for the epipolar images. This results in a softer image but does not increase the model’s accuracy and increases the size of the epipolar images.

Offset X, Offset Y – The offset values move the viewing center for the stereo model. These are needed in close range photogrammetry when there are high camera angles to the object being photographed. For aerial photogrammetry these values are normally set to zero. See View Relative Orientation 3D under the Orientation pull-down for a 3D graphical display of the image geometry.

Image size scale factor X, Image size scale factor Y – These scale factors are used to adjust the size of the area covered by the epipolar images. The area re-sampled is based on the Photo Overlap setting but enlarging the size is needed in some cases. These values are normally set to 1.0 which is no scale factor. See View Relative Orientation 3D under the Orientation pull-down for a 3D graphical display of the image geometry.

Add Model – Pressing this button allows a single model to be added to the list of models. After the model is added the left and right images must be selected and the epipolar re-sampling image parameters must be set. To check the orientation of the left and right images it is possible to go to Orientation -> Relative Orientation to view the left and right images.

Delete Model – Deletes the current model from the model list after verification.

Report – Pressing this button produces a report in a text window about the current file which includes the project name, image names and parameters. The contents of this window may be cut and pasted into another document.

Add Models – Forms and adds models in a batch mode based on the images defined in Define Images. The format of the model names is defined in the Model Name Format dialog box. Options include the ability to include the strip number, left and right numbers and separator characters in the model name. The Update button shows the current format in the upper part of the dialog box based on a strip number of 1 and left and right photo numbers of 2 and 3.

Number of strip characters – Defines the number of characters to use for the strip number at the beginning of the model name. Set to blank to disable the output of this field.

Separator character(s) – Characters may be used to separate the strip number from the next field. Set to blank to disable the output of this field.

Number of left photo characters – Defines the number of characters to use for the left photo number. Set to blank to disable the output of this field.

Separator character(s) - Characters may be used to separate fields. Set to blank to disable the output of this field.

Number of strip characters – Defines the number of characters to use for the strip number. It is possible to include the strip number before the left and right photo numbers. Set to blank to disable the output of this field.

Separator character(s) - Characters may be used to separate fields. Set to blank to disable the output of this field.

Number of right photo characters – Defines the number of characters to use for the right photo number. Set to blank to disable the output of this field.

Update - The Update button shows the current format in the upper part of the dialog box based on a strip number of 1 and left and right photo numbers of 2 and 3.

The Add Model – Epipolar Resampling Parameters dialog box defines the parameters to use during the creation of epipolar images for stereo viewing.

Nearest Neighbor - Fastest re-sampling time, lower quality. High contrast edges will appear more jagged using this mode
Bilinear – Medium re-sampling time, medium image quality. The image quality is softer than nearest neighbor and is normally acceptable for stereo viewing.
Bicubic – Highest re-sampling time, highest image quality. The image quality is the softest of the three methods. Bicubic re-sampling is commonly used when creating orthophotos.

Image size scale factor X, Image size scale factor Y – These scale factors are used to adjust the size of the area covered by the epipolar images. The area re-sampled is based on the Photo Overlap setting but enlarging the size is needed in some cases. These values are normally set to 1.0 which is no scale factor. See View Relative Orientation 3D under the Orientation pull-down for a 3D graphical display of the image geometry.

Delete current models? – Setting this parameter to Yes will delete the current models. WARNING: The deletion of models will delete their model orientations.

Define Images -

The Define Images or Import ImageUtil options are used to identify the images in the project and to assign image parameters such as the photo name format, camera name, strip location and pixel size to each image. If you have already set up a project in Image Utility and performed interior orientations, then use the Import ImageUtil option. This will read the list of images from the Image Utility project, and will automatically recognize the image settings and interior orientation.

Selecting Define Image will display a new dialog box allowing you to add the images to the project. Each image has a camera file, strip location, and pixel size assigned to it. Use this dialog to assign the correct parameters to all images in the project. A camera file must be added to the project from this dialog before adding any photos to the dialog. It is important that the Strip and Photo Num display correctly beside each image. This is controlled by setting the proper Name Format for the images.

Images may be highlighted in the dialog box by placing the mouse pointer on an image and dragging. The shift key plus a mouse click may be used to highlight a range of images and the control (Ctrl) key plus a mouse click may be used to highlight additional images.

The first four rows of the dialog box contain the template to be applied to a group of highlighted images or may be applied to all images. These first four rows contain the project cameras, film strip location, photo pixel size and photo name format.

Project cameras – Up to 10 project cameras can be defined.

Film strip location – The film strip location is the location of the cameras data strip in reference to the rotation of the image. This parameter is not dependent on the direction of flight but the orientation of the image as the user is viewing it. Following is an example of strip locations

The following model consists of Image 1 on the left and Image 2 on the right to construct a model. The data strip is to the left.

The same model as above but the images have been rotated 180 degrees making Image 2 on the left and Image 1 on the right. Along with the image rotation, the strip location is also rotated.

Photo pixel size – The photo pixel size is the actual size of each pixel based on the fiducial coordinate units. This is normally expressed in millimeters but may be in inches or pixels. If the fiducial coordinate units is pixel then the photo pixel size is always 1.

Strip-Photo separator character, Strip digits, Photo digits – These three fields define the Photo Name Format and set the format for decoding the strip number and photo number from and image file name. Please see Photo Name Format for more information about these parameters.

Change Drive (ChaDri)

It is possible to move a job to another directory (folder) and drive and re-define the location of the parameter files needed for orientation and the formation of stereo models. When this command is started the user will be prompted for an existing VrTwo Orientation parameter (.vpr) file. The new locations for the various model orientation parameter files may be defined in the dialog box shown below.

Delete Project (DelPro)

The current project may be deleted using this command. Before the project is deleted a warning dialog box is displayed and the user must confirm the delete.

Import

Import provides methods of orientating stereo models from the results generated by a variety of aerial triangulation programs. The importing of Interior Orientations in batch mode is available along with the ability to import exterior orientations or measurements in single model mode or batch.

There are two methods of performing relative and absolute orientations using Import.

Exterior Orientation – Six independent parameters called the elements of exterior orientation express the spatial position and angular orientation of a tilted image. The process of aerial triangulation determines these six parameters for each photograph and the availability of these exterior orientations for two overlapping images allows a model setup. The values that make up an exterior orientation are Omega, Phi, Kappa, X, Y, Z. The Omega, Phi and Kappa are the rotations about the x, y and z axis of the image and the X, Y and Z is the nodal point of the camera lens which is where the light rays appear to cross in the camera lens.

Measurements – In the process of aerial triangulation over lapping and side lapping images are joined together using pass points for over lapping images and tie points for side lapping images. Each of these points is placed at a common ground location on each photograph. In the process of importing measurements for model orientations these points are read for the left and the right images and relative and absolute orientations are performed. Common point names that have an entry in the coordinate file will be used during the absolute orientation computations.

Please see the document Importing Orientations for more information about these two methods and the various input formats.

Prerequisites:

The user is expected to know information and details of the format that is being imported. The Importing Orientations document should be read before attempting to import model orientations.

Interior Orientations – Batch (IntBat)

In the process of orientating models interior orientations must be preformed on all images before the stereo model can be set. There are several methods to accomplish interior orientations which include:

Manual – Fiducials are measured manually. This method may be started from Orientation -> Left / Right Interior Orientation.

Autocorrelation – Fiducials may be measured automatically using an autocorrelation method using the Vr Image Utility (imageutil.exe) program.

Batch – Interior orientations may be imported from a file or files and applied to each image. The Interior Orientations Batch command performs this operation.

Import orientation file – The ASCII file that contains the interior orientation measurements is defined in this field. The user must know the correct file for the import format. When importing Orima .iop files any .iop file may be selected and all .iop files must be in the same folder as the file selected.

Interior orientation file format – The format of the input interior orientation file may be specified as:

ISAT – The ISAT “photo” file is used to extract interior orientation measurements.

Orima – The Orima format uses the .iop files. Each image must have a corresponding .iop file which uses the same name as the image but with a .iop file name extension.

Corner Interior Orientation – When using images in which the camera has not been calibrated or when using images that do not have fiducials the Corner Interior Orientation to establish a generic interior orientation. When using this format the Import orientation file parameter above does not need to be defined.

Depending on the Interior orientation file format selected one of the following dialog boxes may appear to request more information about the input format:

ISAT

Strip number location - In the ISAT photo file there are two possible locations in which the strip number may be stored. These locations are:

· Embedded with the photo number – The strip number is part of the photo name following the ‘photo_parameters’ keyword. For example, the record:

begin photo_parameters 205 strip_id 2

would assume the strip number and photo number to be included in the 205 field and the 2 after the strip_id would be ignored. If the number of strip characters was 1 and the number of photo characters was 2 then strip 2, photo 5 would be decoded from the 205 field.

· After the ‘strip_id’ keyword – The strip number follows the ‘strip_id’ keyword which is on the same record as the ‘photo_parameters’ keyword. For example, the record

begin photo_parameters 101 strip_id 3

would assume the photo number as 101 and the strip number as 3.

Selecting Images to Orient

The following dialog box is display before importing begins which allows the user to select the images to orient. By default all images are selected.

After completion of each interior the results of the import are placed into the information dialog box.

Exterior Orientation – Single (ImpExt)

The single model exterior orientation input orients a pair of images into a single model by using the six exterior orientation parameters from the two images.

Exterior orientation file – This field defines the file containing the exterior orientation parameters. This file will normally contain the parameters for multiple images which consist of an entire job or a single aerial triangulation bundle adjustment. Please refer to the document Importing Orientations for more information on the various formats.

Exterior orientation file format – This field the format of the file selected in the Exterior orientation file field.

ISAT ‘photo’ File

When importing exterior orientations from the ISAT ‘photo’ file some additional information is required about the location of the strip number.

Strip number location - In the ISAT photo file there are two possible locations in which the strip number may be stored. These locations are:

· Embedded with the photo number – The strip number is part of the photo name following the ‘photo_parameters’ keyword. For example, the record:

begin photo_parameters 205 strip_id 2

· After the ‘strip_id’ keyword – The strip number follows the ‘strip_id’ keyword which is on the same record as the ‘photo_parameters’ keyword. For example, the record

begin photo_parameters 101 strip_id 3

would assume the photo number as 101 and the strip number as 3.

Many of the orientation file formats require additional information about the strip and photo numbers

The Photo Name Format dialog box defines the format for decoding the strip number and photo number from and image file name. Please see Photo Name Format for more information about these parameters.

The two images to use for orientation are selected by choosing the Left photo and the Right photo. The exterior orientation file and number of images read is shown along with the current model at the top of the dialog box.

Mean model ground elevation - The mean ground elevation defines the average ground elevation of the model or job and may be approximate.

Delta Kappa rotation value – Some situations require a rotation angle to be added to the Kappa (rotation about the Z axis) value in the exterior orientation file. This will be required if the images were rotated from their original positions. It is suggested that an angle of zero is first attempted and if the import does not produce a viewable stereo model then a rotation value of 180 should be entered. The possible rotation values are 0, 90, 180 and 270 degrees.

When the import of the model is complete a dialog box will display the model name and the relative and absolute residuals. If these residuals are high the user should try adding 90 degrees to the Delta Kappa rotation value and attempting the orientation again. Pressing the Yes button will start the process of generating epipolar images for stereo viewing. Pressing the No button will skip the generation of epipolar images.

When the import of a model using exterior orientation is complete the VrTwo Orientation program may be exited and VrTwo may be started to view the model. The viewing of the model in relative orientation in the VrTwo Orientation program is not available when this method is used.

Measurement Orientation – Single

The single model measurement orientation input orients a pair of images into a single model by using the common measured points from the two images. These points are typically measured in an aerial triangulation program and are available in a variety of formats.

Once a measurement input format is selected a dialog box is displayed prompting for additional file format parameters. These parameters typically include the photo measurement file name and the coordinate units. Following is the Import PATB Orientation dialog box.