FilterTiePointsByPushbroomModel Task

This task uses the pushbroom model to filter the tie points. Both input images must contain an RPC spatial reference.

For images taken with a pushbroom sensor that have RPC information, the images of the same scene are related by epipolar geometry constraint. For a feature point in the first image, the corresponding point in the second image must lie on the epipolar line or curve. Both images must have RPCs. Imagery from pushbroom sensors use the line central projection. Each scan line has its own projection center, as the following figure shows.

Line central projection

The following diagram shows where this task belongs within an image-to-image registration workflow:

References:

Jin, Xiaoying. ENVI automated image registration solutions. NV5 Geospatial Solutions, Inc. whitepaper (2017). ENVI automated image registration solutions can be downloaded from our website.

Jin, Xiaoying, and Robert Schafer. Method and system for automatic registration of images. Exelis, Inc., assignee; now owned by NV5 Global, Inc. U.S. Patent No. 9,245,201 (issued January 26, 2016).

Example

This example uses sample Quickbird images and a USGS SRTM 1-arc second DEM. The files are available from our ENVI Tutorials web page. Click the Image Registration link to download the .zip file to your machine, then unzip the files. Update the file references in the example with the correct locations.

; Start the application

e = ENVI()

; Open QuickBird images and SRTM 1-arc second DEM

file1 = 'QuickBirdPhoenixWest.dat'

raster1 = e.OpenRaster(file1)

file2 = 'QuickBirdPhoenixEast.dat'

raster2 = e.OpenRaster(file2)

DEMFile = 'PhoenixDEMSubset.dat'

DEMRaster = e.OpenRaster(DEMFile)

; Get the task from the catalog of ENVITasks

Task = ENVITask('GenerateTiePointsByCrossCorrelationWithOrthorectification')

; Define inputs

Task.INPUT_RASTER1 = raster1

Task.INPUT_RASTER2 = raster2

Task.INPUT_DEM_RASTER = DEMRaster

Task.REQUESTED_NUMBER_OF_TIEPOINTS = 40

; Run the task

Task.Execute

; Get the output tie points

TiePoints = Task.OUTPUT_TIEPOINTS

OrthoTiePoints = Task.OUTPUT_ORTHORECTIFIED_TIEPOINTS

; Get the tie point filter task from the catalog of ENVITasks

FilterTask = ENVITask('FilterTiePointsByPushbroomModel')

; Define inputs for the filtering task

FilterTask.INPUT_TIEPOINTS = TiePoints

; Run the task

FilterTask.Execute

; Define outputs for the filtering task

FilteredTiePoints = FilterTask.OUTPUT_TIEPOINTS

; Get the image-to-image registration task

RegTask = ENVITask('ImageToImageRegistration')

; Define inputs

RegTask.INPUT_TIEPOINTS = FilteredTiePoints

RegTask.WARPING = 'Triangulation'

; Run the image-to-image registration task

RegTask.Execute

; Get the output raster

WarpedRaster = RegTask.OUTPUT_RASTER

; Get the collection of data objects currently available in the Data Manager

DataColl = e.Data

; Add the output to the Data Manager

DataColl.Add, WarpedRaster

; Display the result

View = e.GetView()

Layer = View.CreateLayer(WarpedRaster)

Syntax

Result = ENVITask('FilterTiePointsByPushbroomModel')

Input parameters (Set, Get): INPUT_TIEPOINTS, OUTPUT_TIEPOINTS_URI, REPROJECTION_ERROR_THRESHOLD

Output parameters (Get only): OUTPUT_TIEPOINTS

Parameters marked as "Set" are those that you can set to specific values. You can also retrieve their current values any time. Parameters marked as "Get" are those whose values you can retrieve but not set.

Input Parameters

OUTPUT_TIEPOINTS_URI (optional)

Specify a string with the fully qualified path and filename for OUTPUT_TIEPOINTS.

REPROJECTION_ERROR_THRESHOLD (optional)

Specify the reprojection error threshold to use. Specify the reprojection error threshold to use. It is defined as the perpendicular distance (in pixel units) of a point in one image from its corresponding epipolar line computed from a point in another image. The default value is 10.0.