About creating and editing seamlines
ArcGIS Image Server lets you define seamlines that are used when mosaicking the raster data in an image service definition. The images can be feathered (blended) along the seamline to avoid sharp changes in the mosaicked imagery.
There are two methods for generating seamlines. You can either use the option to generate the seamlines by radiometry, which examines the overlap in the raster datasets and intelligently creates a seamline to follow natural patterns between the overlap, or you can generate them by exporting the footprints and optionally shrinking or editing them. The Generate Seamline By Radiometry method creates butt-joined seamlines, and the Generate Seamline By Exporting Footprints method creates seamlines that are overlapped. With either method, you are able to use the editing tools in ArcMap to make modifications to the seamlines.
Learn about seamlines and feathering
About the image service definition Seamline layer
The Seamline layer is added to the image service definition group layer in the ArcMap table of contents once it is generated. This layer represents the seamline shapefile, which is stored within the .ISDef folder. The default symbology for seamlines is a thin, dark blue, hollow polygon.
Right-clicking the Seamline layer in the table of contents presents many of the same options as when you right-click the Footprint layer, with the addition of Shrink Seamline and Generate Seamline. Shrink Seamline moves the edges of the seamline toward the center of the polygon by a specified size. Generate Seamline re-creates the seamline polygons. To manually edit a seamline polygon, use the standard ArcGIS editing tools.
Creating seamlines
Seamlines are created from the Footprint layer context menu. On this menu, you can choose Generate Seamline By Radiometry or By Exporting Footprints. When you generate seamlines using the radiometry method, ArcGIS Image Server generates the seamlines by examining the overlap in the raster datasets and intelligently creates a seamline to follow natural patterns between the overlap. You can choose to generate seamlines for all the rasters in the image service definition, or you can select the footprints using the Select tool to generate seamlines for only a few. This method can only be applied to image service definitions where the output image is 8-bit. For other image service definitions, it is necessary to temporarily change them to output an 8-bit image by applying the stretching process.
Learn about the stretching process
When using Generate Seamline By Radiometry, you get the best results if the footprints are oriented along a north–south axis. If you have a mix of footprint orientations, you will need to orient the display view so one group is oriented north–south, select it, then run the tool on the selected set. Then reorient the display view for the other group, select it, then run the tool again on the selected set. The example below shows the original orientation of the footprints on the left and the rotated data frame containing the same footprints on the right.
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When you generate seamlines by exporting the footprints, the footprint polygons are copied to a seamline shapefile and used as the seamlines.
After creating the seamlines, the Seamline layer will be added to the image service definition group layer in the ArcMap table of contents. Check this layer on to display the seamline polygons. This layer has many of the same properties as other polygon layers in ArcMap, therefore, you can reorder it and change the symbology. There is also a seamline attribute table that can be accessed from the Seamline layer context menu. This table will display an entry for each seamline polygon, along with the properties of each line, such as the feathering width that can be applied to the seamline and whether it will be applied inside or around the seamline.
Learn about applying the seamline mosaic method and feathering
Once the seamlines are created, you can edit them, regenerate them, or export them to a shapefile or feature class.
Editing seamlines
There are two main ways to edit a seamline—using the ArcGIS editing tools and using the Shrink Seamline command. The common ArcGIS editing tools are located on the Editor toolbar. For directions on editing in ArcMap, see An overview of editing and data compilation. You might be specifically interested in adding or deleting vertices, moving vertices, or reshaping the seamline polygons. The Shrink Seamline command is used to reduce the seamline by a specific size. With this operation, the edges of the seamline are moved toward the center of the seamline by a specified amount.
You can also overwrite a seamline polygon using the Generate Seamline command available in the Seamline layer. You can choose to regenerate all the seamlines or just a few, using the Select tool to select one or more seamline polygons.
If you have seamlines saved outside the image service definition or from a separate source, you can import them to use in place of the present seamlines. When adding your own seamlines, keep the following in mind:
- The footprint and seamline shapes must share a common ID.You can apply a join to bring this information together.
- The Seamline layer must exist for you to import new seamlines.Use Export to Seamline to quickly generate seamlines if they don't exist.
- The new seamline dataset must be in the same projection as the image service definition.
- Each seamline polygon should be completely contained within the footprint polygon of the raster.
- There must be a single polygon per footprint.
- The seamline shapefile has to be stored within the .ISDef folder.
- The mosaic method must be changed to Seamline on the Service Properties dialog box.
Once you've added a new seamline to the image service definition, you may need to remove the service from ArcMap and reopen it to view the changes.
Deleting seamlines
If you want to remove the Seamline layer, you need to close the image service definition in ArcMap and delete the seamline shapefile stored within the image service definition's .ISDef folder, or you can use the Edit Seamline tool to delete individual seamlines.