Exercise 2: Automatic vectorization

Complexity: Beginner Data Requirement: ArcGIS Tutorial Data for Desktop

In this exercise, you will edit a scanned parcel map to remove cells from the raster that are not in the scope of the vectorization. Once the raster has been cleaned up, you will generate features using the batch vectorization mode. You will begin by starting ArcMap and loading a map document that contains the raster dataset and two shapefiles.

Setting up the ArcScan environment

Prerequisite:

This exercise builds on the ArcMap settings specified in the previous exercise. You need to have the ArcScan extension enabled, classic editing snapping enabled, and the ArcScan and Editor toolbars displayed.

Steps:

1. Click the Open button on the Standard toolbar.
2. Navigate to the ArcScanBatch.mxd map document in the ArcScan directory where you installed the tutorial data and select it (C:\ArcGIS\ArcTutor is the default location).
3. Click Open.
If you still have the map document open from the previous exercise and are prompted to close it, do so without saving your changes.
4. Raster layers must be symbolized as two-color images to use the ArcScan tools and commands. You will change the raster symbology from stretched to unique values. Right-click the ParcelScan.img raster layer in the ArcMap table of contents and click Properties. The Layer Properties dialog box appears.
5. Click the Symbology tab on the Layer Properties dialog box.
6. Click Unique Values in the Show box.
7. Click OK.

Preparing the raster for vectorization: Raster painting

When performing batch vectorization, it is sometimes necessary to edit the raster image prior to generating features. This process is referred to as raster cleanup and involves the removal of unwanted cells from the raster image that are not in the scope of the vectorization. ArcScan provides the tools to perform raster cleanup. You will now use the Raster Cleanup tools to remove unwanted text from the ParcelScan image.

Steps:

1. Click Bookmarks and click Raster cleanup to set the current view to the edit area of the exercise.
2. Click the Editor menu on the Editor toolbar and click Start Editing.
3. Choose to start editing on the file geodatabase workspace and click OK.
4. On the ArcScan toolbar, click the Raster Cleanup menu and click Start Cleanup to start the raster cleanup session.
5. Click the Raster Cleanup menu and click Raster Painting Toolbar to display the Raster Painting toolbar.
6. Click the Erase tool on the Raster Painting toolbar.
7. Click and hold to erase the text (59.96) located at the top of the parcel lot.
8. Continue to erase the text with the Erase tool until it has been completely removed from the image.
In addition to the Erase tool, the Raster Painting toolbar supports another tool designed to erase cells. This tool is called the Magic Erase tool, and it allows you to erase a series of connected cells by simply clicking or dragging a box around them.
9. Click the Magic Erase tool on the Raster Painting toolbar.
10. Drag a box around the text (001) located in the center of the parcel lot to remove it.

    The text is now removed from the raster.

Preparing the raster for vectorization: Cell selection

In the previous steps, you learned how to use the Erase and Magic Erase tools to remove unwanted cells from the raster image. However, if the image you are working with requires much cleanup, these techniques could be time consuming. To help streamline this process, you can use the cell selection tools in conjunction with the raster cleanup tools.

Steps:

1. Zoom to the bookmarked extent called Cell selection to get a better view of the edit area. Click Bookmarks and click Cell selection.
2. Click the Cell Selection menu and click Select Connected Cells.
3. In the Select Connected Cells dialog box, type a value of 500 for the total area of raster pixels. This expression will select all the cells that represent text in the raster.
4. Click OK. The cells that represent the text in the raster are now selected.
5. Click the Raster Cleanup menu and click Erase Selected Cells to delete the selected cells. The selected cells are now erased.

Specifying the vectorization settings

Batch vectorization relies on user-defined settings, which influence the geometry of the generated features. These settings can vary depending on the type of raster data you are working with. Once you have determined the appropriate settings for your raster, you can save them within the map document or to a separate file. You will use the Vectorization Settings dialog box to apply the settings.

Steps:

1. Click the Vectorization menu and click Vectorization Settings to open the Vectorization Settings dialog box. You will now modify the vectorization settings to ensure optimal results when generating features.
2. Change the Maximum Line Width value to 10.
3. Change the Compression Tolerance value to 0.1.
4. Click Apply to update the settings.
5. Click Close.

Generating features

ArcScan provides a way to preview the batch vectorization prior to generating features. This can help you save time by allowing you to see how the settings will affect the vectorization. When the settings are changed, the preview can be updated by clicking the Apply button located on the Vectorization Settings dialog box. This design allows you to fine-tune the vectorization settings.

The final step in the batch vectorization process is to generate features. The Generate Features dialog box allows you to select the vector layers that will store the new features and execute the vectorization.

Steps:

1. Click the Vectorization menu and click Show Preview. The vectorization preview is displayed on the map.
2. Click the Vectorization menu and click Generate Features.
3. Click the ParcelLinesBatch feature template, if it is not already the active line feature template.
4. Click OK.
5. Right-click the ParcelScan.img raster layer in the ArcMap table of contents and click Zoom To Layer to view all the new features that were generated.
When the display refreshes, you should see the vector features that now represent the raster cells. Once you have finished generating features, you can stop editing and complete the exercise by saving your edits.
6. Click the Editor menu on the Editor toolbar and click Stop Editing.
7. Click Yes to save your edits.
8. If prompted to save your raster cleanup edits, click No.
9. You can close the map document (you do not need to save your changes) and ArcMap when you are done.

You have now completed the ArcScan tutorial. In this exercise, you learned how to use the raster cleanup and cell selection tools to edit a raster layer, apply vectorization settings, preview the vectorization, and generate features. These steps covered the major components of the batch vectorization process.