Blacksburg, VA July 24 th 30 th, 2010 Digitizing and Analyzing Data Page 1

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1 Digitizing and Analyzing Data John McGee Jennifer McKee Prepared by: With support from: NSF DUE in partnership with: Geospatial Technician Education Through Virginia s Community Colleges (GTEVCC) Purpose To learn techniques for generating new spatial features in a layer. To learn techniques for including non spatial data in your final Map Layout (for example, graphs and reports) New Techniques Covered Working with raster data Digitizing from digital imagery Adding X,Y data to a map document Buffering layers Creating a report Creating a graph Adding a graph to a Map Layout July 24 th 30 th, 2010 Digitizing and Analyzing Data Page 1

2 Digitizing Method of converting information from one format to another using a trace methodology. Traditionally, i digitizing i i i has meant the creation of a spatial dataset from a hardcopy source such as a paper map or a plan. Digitizing The old way Heads up Digitizing Uses on screen digitizing, usually with an aerial photograph in the background You are no longer bent over a digitizing tbl table (hence heads up ). ArcGIS provides several tools to support editing July 24 th 30 th, 2010 Digitizing and Analyzing Data Page 2

3 Digitizing Data Most vector spatial data has been digitized from paper maps and aerial or satellite photographs. Digitizing data involves placing a map or photo on a digitizing table and tracing features. Heads up digitizing is digitizing on your monitor, not a tablet. Digitizing Without Tracing Features can also be digitized without tracing. ArcGIS has several tools for creating circles, rectangles, curves, andothershapesofexact of exact dimensions. You can specify angles and lengths of line segments. You can specify that line segments be perpendicular or parallel Points Points are features with no parts. They can be digitized with a single click. Lines have a beginning and ending, and often change direction. i Polygons are lines that return to their origin. July 24 th 30 th, 2010 Digitizing and Analyzing Data Page 3

4 Endpoints The points where a line begins and ends is called an endpoint. The points where a line changes direction or is intersected by another line are called vertices. The segments between vertices are called edges. Endpoints (in red) Vertices (in green) Digitized Line Edges Edit Sketch A feature that has its vertices, edges, and endpoints visible. Once the feature is saved, the vertices, edges, and endpoints disappear and it is no longer an edit sketch. Edit Session All digitizing is done during an edit session. Task: operation you want to carry out Target: layer in which features are being digitized g y g g Tool: software function for completing the task July 24 th 30 th, 2010 Digitizing and Analyzing Data Page 4

5 Tools 9 Tools for drawing edit sketches Grouped on a drop down tool palette called the Sketch Tool Sketch Tool Sketch Tool Creates new features within point, line, and polygon layers Sketch Tool Midpoint Tool Lets you define the location of the next vertex by clicking two points; the new vertex is placed at the midpoint of the line between these points. Example Roads Midpoint Tool July 24 th 30 th, 2010 Digitizing and Analyzing Data Page 5

6 Distance Distance Tool This tool lets you create a point or vertex at the intersection of two distances from two other points. Creates two circles based on two distances and finds two possible intersection i i points i where the primary i can be placed. l Distance-Distance Tool Direction Distance Distance Tool Allows you to create a vertex using a distance from a known point, plus a direction from a known point to define a bearing line. For example, a pole might be located at a specified distance from the corner of one building, and at a defined angle from the corner of another building. Direction-Distance Tool Trace Tool Helps you create new segments that follow along existing segments. Essentially creates parallel line segments Trace Tool July 24 th 30 th, 2010 Digitizing and Analyzing Data Page 6

7 Tangent Curve Tool Adds a segment that is tangential to the previously sketched segment. This tool is practical when sketching rail lines in which the curves are nearly always tangential to the previous segment. Tangent Curve Tool Arc Tool The Arc tool helps you create a segment that is a parametric (true) curve. Arc Tool Intersection Tool The Intersection tool creates a vertex at the place where two segments would intersect if extended far enough. Intersection Tool July 24 th 30 th, 2010 Digitizing and Analyzing Data Page 7

8 Endpoint Arc Tool Allows you to specify the start and endpoints of the curve, then define a radius for the curve. This is particularly useful in sketching cul de sacs, where the beginning and ending points of the arc, as well as the radius of the cul de sac, are known. Endpoint Arc Tool Undo Mistakes You can undo digitizing mistakes with the Undo button on the Standard Toolbar. Or you can use ctrl z Questions? July 24 th 30 th, 2010 Digitizing and Analyzing Data Page 8