There are various ways to get spatial data into ArcView.  You can buy, borrow or steal ready-to-use shapefiles from outside sources; you can use another GIS to import data from standard geodata formats like USGS DLG, and then translate the data into ArcView's shapefile format; you can create event themes of point data; or you can create new point, line or polygon shapefiles yourself in ArcView.   The procedures for creating and editing features in new shapefiles can also be used to edit existing themes.  You can create buffer features that surround existing features.

Event Themes

An event theme is an ArcView Table containing X and Y coordinate fields that let you display the records as point features in a View.  The coordinates can be lat-long decimal degrees, or coordinates in any projection.  If the coordinates are projected, the View should have that projection, as specified in View--Properties.

Unlike point shapefiles, Event Theme Tables can be created, edited or updated outside of ArcView, using any database or spreadsheet program that handles dBase-format data.

To create an Event Theme from scratch, select the Table icon in the ArcView Project window and click on "New" to name and create an empty table, open for editing.  Then Edit--Add Field to create the appropriate fields, then add as many blank records as you like with Ctrl-A (Edit--Add Record).  Then type the data in manually with the Table Edit tool.  It's quicker to enter data by field rather than by record, since the Enter key jumps you to the next record.   You might create a field to allow you to link another table and then copy fields from that.  When you are done, Table--Stop Editing, saving your edits.

To add an Event Theme to a View, add the Table with X-Y coordinates to the Project if it isn't already included, and use View--Add Event Theme.  In the dialog box, specify the Table name and the fields in the Table that contain the X and Y coordinates.  ArcView handles Event Themes just like conventional point Themes.

If you want to create a real point shapefile from an Event Theme, select the Theme and use Theme--Convert to Shapefile and specify the path and name for the new file.

Creating and Editing Point Shapefiles

On-screen digitizing of shapefiles is generally performed on a background airphoto, scanned USGS quad map or satellite image that is included as an image Theme in the View.  First, select the background image that you will use for visual referencing of your new features, and add it as a Theme in the View where you will be doing the digitizing.

To create a new point shapefile, activate the View you will add it to, select View--New Theme, select "Point" as the feature type, and specify a path and name for the new shapefile.  The empty shapefile will be added to the View as a new Theme.  Alternately, to open an existing shapefile for editing, select the Theme in the View, and use Theme--Start Editing to open the shapefile for edits. You will notice that the Theme's check-box in the View's legend has a dashed border, indicating that the shapefile Theme and its attribute Table are open for editing.

Now add point features to the shapefile, using the Draw Point tool.  This will be the only available tool  in the Drawing tool pulldown menu since this is just a point Theme; the other tools will be greyed out.  Each left mouse click in the View will create a new point feature and an empty attribute record for it in the Theme's attribute Table.  Delete any erroneous points with the Delete key.  Reposition points as necessary by selecting them with the pointer and dragging them in the View.  You can undo an erroneous delete or move with Ctrl-Z (Edit--Undo Feature Edit).

To add attribute data for your new points, first use Table--Add Field to define and add appropriate fields.  Then activate the View and use the Pointer tool to select each point in the View; the associated attribute Table record will be highlighted; use the Table Edit tool to click on the successive fields in that record and type in the data.

Creating and Editing Line Shapefiles

To create a new line feature shapefile, activate the View, use View--New Theme, select "Line" as feature type and specify path and filename.  The empty shapefile will be added to the View as a new Theme.  Or select an existing Theme in the View and open it with Theme--Start Editing

Since you are creating line features, you have two available Drawing tools: Line Draw and Line Split.   Use the Line Draw tool to create conventional lines in the View: for each line, click the start point and successive shape points, then double click the end-node.  Use the Line Split tool to create lines that split each other at intersections.  When using the Line Split tool, both the line being drawn and any line it intersects are split into separate features at the intersection point, which becomes an end-node for four lines.  Note that lines drawn with the Line Split tool must cross other lines, or they won't be created.

The Line Split tool  provides an easy, elegant way to insure topologic consistency in your line data.  For example, if you are digitizing a stream network, you could digitize the main stream to its origin, then draw the tributaries with the Line Split tool so that they overshoot the main stream, then select and delete the overshoot segments.  This procedure will yield a network of perfectly-connected stream reaches.

Snapping

Another way to insure topologic consistency is to activate ArcView's snapping capabilities, so that the vertices of lines you are drawing will snap to connect automatically with other features if the new vertices fall within a specified snap tolerance distance of those features.   Snapping thus corrects for small undershoots and overshoots of line intersections.  When digitizing  roads, for example, you can snap as many road segments as necessary to the same intersection point.

Snapping can be either general or interactive.  General snapping works automatically: a new feature's vertex will snap straight to a line segment of a nearby feature; it doesn't need to snap to an existing vertex in the feature.  Interactive snapping lets you specify what your next vertex should snap to--the nearest vertex; the nearest line, the nearest line endpoint, or the nearest intersection of two or more lines.

You can activate general or interactive snapping (or both!).  The easiest way is to right-click the mouse in the View window and enable either method in the pop-up menu.  The selected Snap tool (   is the interactive tool) will then appear next to the Draw tool.  To set the snapping tolerance with the mouse, click the Snap tool next to the Draw tool, and then drag a circle in the View to set the tolerance (the circle's radius, displayed at the bottom of the ArcView window).

With  interactive snapping, when you are drawing a new line with left mouse clicks and approaching a feature you want to snap to, right-click the mouse to choose the type of target to snap to--vertex, boundary, intersection or endpoint--then just add the next new vertex close enough to the snap target.

Line Splits and Unions

Each time you use the Line Split tool, you actually create three additional features at each intersection: the two new segments plus the segment split off the existing line feature.

If you want to union multiple line features into a single feature, select the lines to be combined with the Pointer tool, and Edit--Union Features.

ArcView adds a new record in the Theme Attribute Table for each new line feature.  As noted previously, you can add new fields to this Table or enter attribute data for your new line features at any time.  If you want to split or union features that already have attribute data, ArcView also lets you select attribute updating rules for each field in the Theme--Properties Editing window.  These rules specify how unions and splits should be handled for each field.  When splitting a line in two, for example,  you can copy the field's value to both the new features, split the field's value in proportion to the  relative lengths of the new lines, or leave the new features' field blank.  When creating a union of two or more lines, you can sum or average the source records'  field values, keep the field value from first-listed record, or leave the field blank.

Editing Line Vertices

Use the Vertex Edit tool (arrowhead outline next to the Pointer tool) to select a line, shared segment or shared end-node for editing.  Then you can move or delete any mis-placed vertices, or add additional vertices.  To move a vertex, click and drag it.  To add a vertex, click where you want it to go.  To delete a vertex, click it and press the Delete key.

• If you select a single line, the vertices belonging it are denoted by little squares.  Edits will affect only that line.
• If you select an end-node shared by two or more lines, the end-node is denoted by little squares, and the nearest vertices on each line are denoted by little circles.  Edits will affect all lines sharing the end-node.

Creating and Editing Polygon Shapefiles

Same set-up: activate the View, View--New Theme, select "Polygon" as feature type and specify path and filename.  Or Theme--Start Editing an existing polygon Theme.  Enable snapping and set the snapping threshold as with line drawing (above).

ArcView provides five polygon drawing tools.  The most useful are the Autocomplete and Split tools, which maintain boundary topology.

• The Autocomplete tool creates a new polygon contiguous to one or more existing polygons.  Draw the polygon boundary starting and ending inside an existing polygon, double-clicking the final vertex; the existing polygon will automatically clip out the area of the new polygon that overlaps it, making the new polygon perfectly contiguous with its neighbor.
• The Polygon Split tool sections a piece of an existing polygon as a new polygon.  Draw the new polygon starting and ending  outside the existing polygon, double-clicking the final vertex; the new polygon will be clipped from the existing polygon.

• To merge a set of polygons into a single polygon, select the polygons with the Pointer tool and Edit--Union Features.
• To create a polygon with a void area inside a it, draw the exterior boundary of the polygon, then its interior boundary with the Polygon tool, select both polygons, and use Edit-Combine Features to cut out the interior polygon area.
• To resolve  polygon overlaps, select the polygon that will get the overlap, then the polygon to cede the overlap, then Edit--Subtract Features.  This utility also supports creation of a polygon completely contained within another polygon.
• To extract the area where two polygons intersect, select the intersecting polygons, and Edit--Intersect Features.

You can edit polygon vertices with the Vertex Edit tool the same way you edit line vertices:

• If you select a single polygon, the vertices belonging it are denoted by little squares.  Edits will affect only that polygon.
• If you select a boundary segment shared by two polygons, the vertices are denoted by little circles.  Edits will affect both polygons.
• If you select an end-node shared by two or more polygons, the end-node is denoted by little squares, and the nearest vertices on each line are denoted by little circles. Edits will affect all polygons sharing the end-node.

Once you have completed your edits to the Theme, Theme--Stop Editing, saving your edits.

Digitizing from Hardcopy

Do this only as a last resort!  Digitizing from hardcopy maps is about the worst possible way to acquire spatial data.  The Spatial Analysis Lab still has the old digitizing tablet and lots of rolled-up paper maps, but nobody wants to do conventional digitizing anymore: it's complicated, error-prone and very tedious.  Paper maps are prone to distortion from head and moisture, and this distortion error is only compounded by the eye-hand error of the person doing the digitizing.  We used to hire and train undergraduates to do our digitizing, but they all ran away.