When you use ArcGIS to digitize the map, or load the Raster image to an existing coordinate system map, the first task is to perform spatial registration of the map.
You can use the georeferencing tool to configure the raster images on time. The spatial adjustment tool can be used to timely match existing GIS images with other coordinate systems or maps.
1. Use the georeferencing tool to register raster images
Load a grid chart in ArcGIS, which can be a photo or a scanned image. If the georeferencing toolbar is not displayed, right-click the toolbar and select georeferencing. After a grid chart is loaded, the georeferencing toolbar is activated. If multiple images are loaded, select the image to be registered at the layer.
Click georeferencing in the georeferencing toolbar to cancel the Auto Adjust option. You can select the method used for spatial transformation in transformation.
Click Add Control Point in the georeferencing toolbar to add a control point. The principle of spatial registration using georeferencing is to enter new correct coordinates for specific points on the raster map. At this point, you can set the new coordinates in two ways:
(1) After clicking a point, move the location directly and click again on the new point to be registered, a connection is established between the two points.
(2) Click a point, right-click it, and in the pop-up dialog box, click Enter X, Y, and then enter the absolute coordinates of the point.
In order to make the registration result as accurate as possible after spatial registration, you can set several control points (as far as possible around the average of the places of interest ). After setting, you can click Auto adjust or update display in the georeferencing toolbar for registration. The registration result is displayed. If you are not satisfied, you can also adjust the local control points, and then click it to manually.
After registration, use the update georeferencing or rectify command in the georeferencing toolbar to save the registration result. The former generates a jgw file to store the registration coordinate information, while the rectify command saves another registered image file.
2. Use spatial adjustment to register
The spatial adjustment and georeferencening tools have similar steps and principles. Also, create multiple registration control points and click the adjust command for registration.
