Tie-Point Refinement module

Name	Caption
Input Project Files	Input OrthoEngine project file or MFILE of project files
Output Project	OrthoEngine project file to which to write the results
Output Report	Name of the accuracy report file to create
Overwrite Results	Overwrite existing results
Thin Tie Points	Whether to thin tie points
Refine Tie Points	Whether to refine tie points
TP Rejection Method	Tie point rejection method
TP Rejection Method Thresholds	Tie point rejection method thresholds
Rejection Limit Percentage	Maximum percentage of TPs to eliminate per iteration
Rejection Action	Remove or deactivate TPs rejected during thinning and refinement

Parameter descriptions

Input Project Files

The path and file name of a valid OrthoEngine project file (oe.prj). Alternatively, you can specify an MFILE as input. The MFILE must contain OrthoEngine project files. When you specify an MFILE, all of the OrthoEngine project files in the file are merged into a single OrthoEngine project, which is then refined by the module.

Output Project

The path and file name of the OrthoEngine project file to which to write the results of the refinement.

Output Report

The path and file name of a text file in which to write the report about the refinement. When no value is specified for this parameter, a report is created using a default file name, , in the folder you specified for your output project.

Overwrite Results

Select this check box to overwrite the existing output files, if any exist. If this check box is left clear, and an output file exists in the relevant folder, the status of the job displays a message informing you of the existence and name of the output file. The message is also written to the event log of the job.

Thin Tie Points

Select this check box to thin the number of tie points (TP) collected.

That is, sometimes TP collection can gather too many points on each image. The distribution of the points may also be too varied. By thinning the points, you can reduce the number collected and distribute the points more consistently. Computation time is also reduced, because the detection of points requires less effort.

Refine Tie Points

Select this check box to refine the tie points collected. If this check box is left clear, you must verify and, if necessary, manually refine the tie points.

TP Rejection Method

The method used to reject tie points (TP).

Available options are:

Automatic: RMS error and sigma (standard deviation) rejection methods, measured in pixels
RMS Error (Pixel): RMS error-rejection method, measured in pixels
Standard Deviation (Pixel): sigma (standard deviation) rejection method, measured in pixels
Percentage: percentage of points that can be rejected, starting with the one with the highest residual
Absolute Distance (Pixel): absolute distance rejection, in terms of the residuals, measured in pixels
Absolute Number: absolute number of points to reject, starting with the ones with the highest residual

You can specify various values for this parameter, depending on the method selected.

TP Rejection Method Thresholds

The rejection threshold values for the value selected for the Rejection Method parameter.

This parameter is defined using two values (THRESH1, THRESH2); these differ in meaning depending on the selected rejection method:

Automatic: rejection starts by removing the top 5 percent of TPs with the largest residual values that are greater than plus-minus three (±3) standard deviations, and then recalculates the math model. This is performed three times when the number of TPs is less than 100,000, and performed only once when the number of TPs is equal to or greater than 100,000. The rejection method then removes all TPs that are plus-minus three (±3) standard deviations and recalculates the math model. The refinement procedure ends when:
1. RMS is less than 0.5 pixels
2. Improvements to the RMS are less than 0.05 pixels
3. Maximum number of iterations has been reached
The maximum number of iterations is 10 when the number of TPs is less than 100,000, and five when the number of TPs is equal to or greater than 100,000.
RMS Error: rejection starts from the point with the largest residual error for any point, and then recalculates the math model and RMS error. If the RMS error is still above the specified thresholds, the point with the next highest residual is removed and so on, until the x-RMS and y-RMS errors are equal to or less than THRESH1 pixels or THRESH2 pixels.

For example, a value of 2,2 rejects points with the highest residuals until the x-RMS and y-RMS are both less than two pixels.
Standard Deviation: THRESH1 and THRESH2 represent the minimum standard deviation values of the x and y residuals to be rejected, respectively.

For example, a value of 2,1 rejects points that have a standard deviation higher than two of the resX mean, and rejects points that have a standard deviation higher than one of the resY mean.
Percentage: THRESH1 represents the percentage of the number of points to be rejected and THRESH2 represents the ratio weighing between the x and y residuals. For example, if you set a rejection weight of 2, you are giving twice the weight to the x-residual (resX) as to the y-residual (resY). By default, the residual in x and y have the same weight. Therefore, if you have a point with a resX of 0.4 and a resY of 0.5, the point is given a resX of 0.8 and a resY of 0.5 for the rejection.

For example, a value of 5, 2 rejects five percent of TPs, and gives the x-residual (resX) twice the weight as that of the y-residual (resY).
Absolute Distance: THRESH1 and THRESH2 represent the minimum absolute x and y pixel residuals to be rejected. The rejection starts from the point with the largest x or y residual distance.

For example, a value of 2,2 rejects points with a resX of greater than two pixels, and rejects points with a resY of greater than two pixels.
Absolute Number: THRESH1 represents the number of points to be rejected and THRESH2 represents the ratio weighing between the x and y residuals. For example, if you set a rejection weight of 2, you are giving twice the weight to the x-residual (resX) as to the y-residual (resY). By default, the residual in x and y have the same weight. Therefore, if you have a point with a resX of 0.4 and a resY of 0.5, the point is given a resX of 0.8 and a resY of 0.5 for the rejection.

For example, a value of 10, 0.5 rejects 10 TPs, and gives the x-residual (resX) half the weight of the y-residual (resY).

Rejection Limit Percentage

The maximum percentage of the initial number of TPs to eliminate per refinement iteration.

Rejection Action

Select whether to remove or deactivate tie points (TP) rejected during thinning and refinement.

The available options are as follows:

Deactivate: renders rejected points inactive. Inactive points are excluded from the math-model calculation.
Delete: removes rejected points.

Details

General job details

Preprocessing requirements

Before running this module, the following requirements must be met to ensure the job processes successfully and produces accurate results:

Input Project Files: the OrthoEngine project you specify as input must contain tie points (TP). If you specify an MFILE, all of the OrthoEngine project files being merged must have the same characteristics, such as projection, math model, and so forth.

Module details

The Tie-Point Refinement module reads the input project files, merges them into a single OrthoEngine project file, refines all of the TPs found, ensuring that they meet the specified accuracy requirements, and then generates a summary accuracy report.

Job results

The Tie-Point Refinement module produces the following output:

Final CATALYST Professional OrthoEngine project file.
Report, in text format, for the merged and final OrthoEngine project file.
Summary accuracy report, in text format, for each image processed.

You can now open the scenes in CATALYST Professional Focus or open the OrthoEngine project file in OrthoEngine to perform QA, or proceed to use the next module in the CATALYST Enterprise workflow. Typically, this is to use one or both of the following:

DEM Extraction module
Orthorectification module

Tie-Point Refinement module

Description

Parameters

Parameter descriptions

Details