This is the 17th day of my participation in the August Challenge
1. Image correction
Actual operation process often encounter such a situation, two image data of the same coordinate system, superposition together may occur when the data stack together, have a plenty of difference of a few millimeters distance a little, can rush to the dead, especially in patients with ocd can’t stand, so we must be on the correction operation, the following figure
2. Rectification procedure
(1) Use ArcMap to open the image to be corrected and the standard image or vector (only if it can be compared correctly)
(2) If the image has a black edge, remove the black edge uniformly
On the toolbar, select Windows -> Image Analysis -> Select all image files -> Background
(3) Swipe tool was used to compare two image deviations
Take a small image as an example
As shown in the figure above, at the bottom of shanxi_84.tif, compare the first image with the second image. Select the first image at position 1, click the button at position 2, and then go back to the image and drag the mouse up and down
(4) Establish reference points according to standard images or SHP
Start by creating a vector of reference point data
Then, according to the standard image, add several reference points with reference value, and then move the image to be corrected according to the reference points. Note that the coordinate system selected in the table between the reference points should be consistent with that of the standard image
The following figure shows the reference points added according to the standard image, and the following figure shows the customized reference points based on the small image. Several more reference points can be added. After the reference points are added, the editing state can be stopped for the next step of correction
(5) Correct deviation according to reference points
Open ArcMap and add Georeferencing toolbar (Customize–>ToolBars– >Georeferencing check)
From the Georeferencing toolbar, select the shanxi_84.tif image you want to correct, then click on the shift icon in the bottom right corner of the box above.
The first option Rotate, the third Scale, and then move the shanxi_84 image to align with the reference point, as indicated below
(6) Save the corrected image
This image accuracy is not high, zoom to a certain extent can not see clearly, the key points can make do, if the accuracy of the requirements can be downloaded more accurate image, so that the correction effect is better, in this only for demonstration use
Export select image right click property –data– > Export Data — modify property — Save, as shown below
3. Registration procedure
If the image is converted to the corresponding coordinate system by accurate parameters, the import can accurately match the vector data without manual registration.
(1) Open ArcMap and add Georeferencing toolbar (as shown in the figure).
Customize–>ToolBars—>Georeferencing
(2). Do not select Auto Adjust from the Georeferencing menu of the Georeferencing toolbar.
(3). On the Georeferencing toolbar, click the Add Control Point button.
(4). Click the reference point on the image, and then click the corresponding reference point on the vector.
(5). Click the previous step to add one or more control points. Under the Georeferencing menu, click Update Display.
(6). Under Georeferencing menu, click Rectify to save the calibrated image.
4. Rotate the coordinate system
4.1 ArcMap Projection transformation
Usually can directly convert the coordinate system, ArcMap provides conversion tools, as shown below
In the ArcToolbox, click Data Management Tools → Projections and Transformations → Raster → Project Raster. The projection transformation dialog box (as shown below) pops up;
4.1.1 Parameter Description:
Input Raster: The source image image to be converted.
Source Coordinate System: Automatically reads the Coordinate information of the source file. In this example, the source coordinate system is the WGS84 geographic coordinate system.
Output Raster Dataset: Select the file name of the Output image and add the suffix “. Tif “.
Output Coordinate System: Target Coordinate System to be converted to. In this case, it is necessary to convert to meridian 117E of Beijing 54 Gaussian projection 3 degree belt.
Geographic Transformation: A conversion parameter between the target coordinate system and WGS84 coordinate system (ToWGS84).
4.1.2 faults:
But some can’t direct conversion needs us to offer three or seven parameters, and these parameters is confidential data, and the parameters of each place is different, the average person have no way to obtain, so someone will think of several points to obtain the parameters of the custom, but this error is relatively large, but we must solve this problem again
After understanding, the net has a lot of software to be able to realize the coordinate system conversion, such as Bigemap, too happy map and so on the use method is very simple, tried the conversion effect can also
4.2 Taile map conversion method
Taking Taile map as an example, the coordinate system of Xi ‘an 80 is transformed into WGS84
2 steps
(1) Open the tool — Coordinate system transformation
(2) Select source file projection (select by file)
(3) Add the files that need to transform the coordinate system
(4) Output options – save format select IMG format for large files and tif for small files
(5) Output option – Select projection target coordinate system
(6) Optional output path
(7) Resampling algorithm selects the second bilinear sampling
Resampling algorithm affects the image conversion quality, the better the quantity, the slower the relative speed, can be selected as required.
(8) Conversion
4.2.2 shortcomings
Advanced features of the software are charged, you can download a free version of the trial
4.2.3 Green Web Disk Address
Seniors to provide only learning to use
Access code: 7JTW
—The end—-
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