GIS@Grinnell : Training

Tablet Digitizing

Before you can begin digitizing with a digitizer, you must do the following:

1. Set up Datasets

   1. Open ArcCatalog.

   2. In appropriate computer or network location select New >> [prefered spatial data type].

   3. Select Data Type – Point, Line, Polygon and other attributes as needed.

   4. Select appropriate Projection/Coordinate System.

   5. Select appropriate X and Y extents.

2. Set up Map Project.

   1. Open ArcMap.

   2. Add Data Frame.

   3. Add newly created Data Source.

   4. Make New Data Source active (if necessary).

3. Set up your digitizing tablet and install the driver software.

   1. Hopefully this has already been done for you.

   2. If necessary connect the tablet and turn it on.

   3. If necessary in \arcgis\arcexe81\bin type “regsvr32 digitizer.dll”.

4. Configure the digitizer puck buttons.

   1. Hopefully this has already been done for you.

   2. If necessary, using TabletWorks icon in task tray, configure one button for 'left click' and one for 'double left click' (remember which is which).

5. Ensure the quality of your paper map.

   1. Your map should ideally be reliable, up-to-date, flat, and not torn or folded. Paper expands or shrinks according to the weather. To minimize distortion in digitizing, experienced digitizers often copy paper maps to a more stable material such as Mylar.

   2. Of course, most people are too lazy to do all of the above, but do it anyway. You will thank me later.

6. Establish control points on the paper map.

   1. Before you can begin digitizing from your paper map, you must first establish control points that you will later use to register the map to the geographic space in ArcMap. If your map has a grid or a set of known ground points, you can use these as your control points. If not, you should choose between four and 10 distinctive locations such as road intersections and mark them on your map with a pencil. Give each location a unique number and write down its actual ground coordinates.

   2. Once you’ve identified at least three well-placed control points, place your map on the tablet and attach it with drafting tape. You don’t have to align the map precisely on your tablet; ArcMap corrects any alignment problems when you register the map and displays such adjustments in the error report.

7. Register the paper map.

   1. After adding a layer to your map, click the “Editor” menu and click “Start Editing”.

   2. Click the “Editor” menu and click “Options”.

   3. Click the “Digitizer” tab.

   4. With the digitizer puck, digitize the control points you established earlier (see in the Online Help >> Getting ready to digitize: an overview).

      1. With the puck over each control point on the map, press the button you configured to perform a left mouse click.

      2. A record appears in the X Digitizer and Y Digitizer columns for each control point you digitized.

   5. Type the actual ground coordinates for each control point in the X Map and Y Map fields.

      1. This can be done after each control point is digitized or after all control points or digitized.

   6. Errors in map units and paper units are displayed for each control point.

      1. The error is called the root mean square (RMS).

   7. Save control points for future use (optional).

      1. Click Save to save and type a name for the control point file.

      2. In the future simply choose “Load” and then digitize the corresponding control points.

   8. If the RMS is acceptably low click the “Enable” checkbox.

   9. Click “OK” to register the map and close the Editing Options dialog box.

8. Digitize paper map features.

   1. See the feature editing How-To for details.