ENVI "Geometric correction of image preprocessing in remote sensing image"

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First. Overview of image geometry correction

1. Geometric correction method:

1) geometric correction using satellite's own geo-location file. The main menu >>>map>>georeference the name of the sensor to start the corrective method.

2) image to image geometry correction. An image does not have a geometric correction of deleted files or has been geometrically corrected raster files as a datum map, the two images by selecting the same name point to register another raster file, so that the same figures appear in the same position after correction, most of the geometric correction is done by this method.

Select the main menu >>map>>registration>>select gcps:image to Image.

3) Image to map geometry correction.

Through the ground control point to the remote sensing image geometry plane process, the control point can be input by the keyboard, from the external vector file or raster files obtained. The correction of topographic maps can be used in this way.

Select the main menu >>map >>registration>>select gcps:image to Map.

4) image to image registration automatically.

The registration process of two images is completed automatically based on the pixel grayscale values or feature features, and the same name points on the two graphs are searched. When two images in the same area are imaged by their respective corrected errors, the same figures on the graph can be adjusted using such methods when they cannot overlap.

Select the main menu >>>map>>registration >>automatic registration:image to Image.

2, the control point selection method:

1) Select from the raster image.

If you have a corrected image, topographic map, and other raster data that need to correct the image area, you can select a control point from which the control point selection mode is image to image.

2) Select from the vector data

If you have corrected vector data for the area of the image that needs correction, you can select the control point from which the corresponding pattern is image to Map.

3) Select from a text file

In advance, through GPS measurement, photogrammetry or other ways to obtain the control point of the coordinate data files, can be directly imported to use.

4) keyboard input.

3, geometric correction of the computational model

ENVI offers three computing models:

Affine transformation (RST).

Polynomial model (polynomial).

Local triangular network (triangulation).

4, the method of punching sampling

1) Nearest neighbor method.

2) bilinear interpolation method.

3) Three-time convolution interpolation method.

Second, geometric correction based on strip location information

The following steps are described:

The first step is to open the data file.

The HDF file format is a self-descriptive, extensible, self-organizing storage format that can be used in most scientific research.

Select the main menu >>open External File>>eos>>modis Select 500M file to open.

Envi automatically extracts header files, including information such as geo-reference information, sensor parameters, and so on.

Step Two: Select the calibration model

Select the main menu >>map>>georeference the MODIS File dialog box, click the file name to view the text information on the right. Select the corrected file click OK to proceed to the next step. The Georeference MODIS paramentres dialog box appears.

Step three: Set input parameters

1) Set the output coordinate system in the Georeference MODIS paramentres dialog box.

2) Type the number of XY-direction correction points in # Wrap point, and the number of correction points in the X-direction should be less than or equal to the number of corrections points in the 51,y direction.

3) You can export the correction point to a control point file: pts.

4) The Perform Bow Tie correction option is used to remove the "butterfly Effect" and the default is yes.

5) Click OK to enter the registration Parameter (Correction Parameters) dialog box.

6) In the Correction Parameters dialog box, the system automatically calculates the starting point coordinates, cell size, and so on.

7) Click OK to perform the georeference of the MODIS data.

Third. Geometrical correction of FY3 meteorological satellites based on GLT

The GLT geometry correction method uses the input geometry file to generate a geolocation lookup table file from which you can learn the geographic location of an initial cell in the final output.

The GLT file contains the geographic information for each cell of the initial image, and its correction accuracy is high, avoiding the processing of low-resolution image data using two-time polynomial geometry correction through ground control points.

The procedure is as follows:

First step: Install the plugin. Add a envi under the HDF5 format to read the patch and restart the ENVI.

Step Two: Open the file

1) Select the main menu >>file >>open External file >>gerneric formsats>>hdf5. select files.

2) in the file contains a lot of information, select REFSB, in the dialog box can be browsed.

3) Click Import to ENVI and load into the ENVI bands list.

4) The same method opens the file for locating latitude and longitude (latitude and longitude)

Step three: Generate the GLT file

1) Select the main menu >>map georeference from Input georeference>>build GLT.

2) longitude as the X-band, set the samples to 3 in the Select Spatial subset.

3) The latitude is the Y-band.

4) georeference Projection information fill out the output projection parameters.

5) Fill in the file path of the cell size and output.

Fourth step: Using GLT to correct the image

1) Select the main menu >>map >>georeference from Input georeference>>georeference from GLT.

2) In the File dialog box, select the appropriate GLT file and the file to be corrected.

3) Set the output path and file name in the Output dialog box.

4) The results of the output are automatically loaded into the bands list. Select the appropriate bands to be displayed in display.

Fifth Step: View results

Select the main menu >>spectral>>spare Tools >>google Earth Bridge, the correction results are superimposed on Google Earth and you can see the results of the correction and Google Earth is basically coincident.

Fourth, image to image geometry correction

This example is based on the Spot4 panchromatic band and carries out the geometric correction process of the LANDSAT5TM image.

First step: Open and display the image

Select the main Menu >>file>>open Image File displays bldr_sp.img and tm.img respectively in display.

Step two: Start the Geometry correction module

1) Main Menu >>map>>registration>>selectgcps:image to Image, open the Geometry correction module.

2) Select display for the spot file to be the reference image, TM displays for the image to be corrected, click OK button, enter the acquisition ground Control point.

Step three: Collect ground control points.

1) Control Point Tool dialog box

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ENVI "Geometric correction of image preprocessing in remote sensing image"