GIS 1 GIS Lecture 6 Digitizing

GIS 2 Outline Digitizing Overview Digitizing Sources GIS Features Creating and Editing Shapefiles in ArcView Spatial Adjustments Conclusion Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 3 Digitizing Overview

GIS 4 Why Digitize? New maps Map features are wrong Missing features Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 5 Heads Down Digitizing Digitizing table or tablet Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 6 Heads Up Digitizing Mouse on a screen Digitizes paper maps, aerial photos, or other images Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 7 Digitizing Sources Orthophotos GPS Paper Maps Scanning Raster to Vector Conversion Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 8 Orthophotography Digital imagery in which distortion from the camera angle and topography have been removed, thus equalizing the distances represented on the image Can be used to measure true distances Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 9 DOQQs Digital Ortho Quarter Quadrangles Produced by the U.S. Geological Survey (USGS) Grayscale or color-infrared (CIR) images 1-meter ground resolution; Cover an area measuring minutes longitude by 3.75-minutes latitude, approximately 5 miles on each side Referenced to the North American Datum of 1983 (NAD83) and cast on the Universal Transverse Mercator (UTM) projection. Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 10 Image Resolutions The amount of detail found in one pixel of the image. image with one meter resolution means that each pixel in the image represents one square meter on the ground. 30 meters 10 meters 5 meters Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 11 Image Resolutions (Continued) 2 meters 1 meter Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 12 Resources Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 13 Resources (Continued) Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 14 Resources (Continued) Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 15 Resources (Continued) Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 16 Resources (Continued) Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 17 Resources (Continued) Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 18 Resources (Continued) Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 19 Resources (Continued) Google Maps Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 20 Resources (Continued) Google Earth

GIS 21 GPS Department of Defense built the global positioning system (GPS) in the 1970s Network of up to 24 satellites in earth orbit Opened it up to civilian use in the 1980s – free of charge GPS uses triangulation from signals from the satellites Base stations are fixed receivers that help GPS signals get accuracy within 1 to 5 meters

GIS 22 GPS (Continued) Easy to input GPS data into GIS GPS is most valuable when there are no base maps sufficient to guide drawing new features

GIS 23 National Spatial Reference System National network of control points (small brass disks with identifiers and marks) placed on permanent structures such as concrete posts National Geodetic Survey (NGS) establishes the known points Surveyors take measurements (angles and distances) from known locations to accurately locate points and boundaries By the early 1990s, GPS became the dominant method for establishing control points Some cities maintain their own points

GIS 24 National Spatial Reference System City of Pittsburgh control point benchmark

GIS 25 Paper Maps Historic Maps Historic maps of Pittsburgh and Allegheny County from Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 26 Scanning Paper Documents Scanned maps and images become vectors Special software needed Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 27 Raster to Vector Conversion Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 28 Raster to Vector Conversion Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 29 GIS Features

GIS 30 Points Nodes - Single points - Alone or at endpoints of lines 0 0 node Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 31 Points Vertices - Control the shape of lines 0 0 node vertex Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 32 Points Tics - control points used to register the map to the geographic space 0 0 node vertex tic Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 33 Lines Connected Nodes and Vertices Single or multipart features 0 0 node 1 2 line Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 34 Lines From Node To Node Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 35 Line Features with Vertices Vertex Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 36 TIGER LINE Files Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 37 TIGER Street Centerlines Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 38 TIGER Street Centerlines Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 39 Polygons Closed lines Single polygons or multipart features (e.g. Hawaiian islands can be multiple polygons as one feature) 0 0 node 1 2 polygon 43 Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 40 New Shapefiles

GIS 41 Creating New Shapefiles Create new point, line or polygon shapefile in ArcCatalog Add Spatial Reference Information (optional) Add New Shapefile in ArcMap Edit shapefile to add features and attributes Stop editing Save edits as part of new shapefile Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 42 New Shapefiles - ArcCatalog Cannot create shapefiles in ArcMap Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 43 Add Shapefile in ArcMap Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 44 Heads Up Digitizing Add base layers if necessary Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 45 Heads Up Digitizing Add Editor Toolbar Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 46 Heads Up Digitizing Start Editing Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 47 Heads Up Digitizing Begin Digitizing Click Sketch Tool Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 48 Heads Up Digitizing Start Drawing Points

GIS 49 Heads Up Digitizing Stop Editing Save Edits

GIS 50 Heads Up Digitizing Add attribute information

GIS 51 Editing Shapefiles

GIS 52 Lines and Polygons Advanced editing tools - Editing Vertices - Snapping Functions - Multipart Features Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 53 Editor Toolbar Editor Toolbar Sections - Editor drop-down - Sketch tool - Tasks - Target - Attribute Inspector - Sketch properties Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 54 Sketch Construction Tools Sketch tool: Use to create point features and to digitize the vertices of line or polygon features. Intersection tool: Creates vertex at place where two segments intersect Arc tool: Creates a segment that is parametric (true) curve. Only has two vertices as endpoints Midpoint tool: Define the location of the next vertex by on two points - the vertex is place at the midpoint of the line between these points End Point Arc tool: creates true curve by defining the start and end points of the curve, then define a radius Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 55 Sketch Construction Tools Tangent Curve tool Creates segments that are tangent Distance-Distance tool Creates a point or vertex at the intersections of two distances from two other points Direction-Distance tool Like distance-distance tool except second point uses a direction from a known point to define a bearing line Trace tool: Create segments that follow along existing segments Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 56 Tasks Most features are created and modified through sketches Tasks define what you do with a sketch Create features Modify features Reshape features Other edit tasks Custom tasks Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 57 Target Layer Target layer determines to which layer a new feature will belong Can edit multiple layers in an edit session Subtypes are also listed* Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 58 Spatial Adjustments

GIS 59 Spatial Adjustments Transform Rubbersheet Edgematch Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 60 Transforms Convert data from one coordinate system to another. Converts data from digitizer or scanner units to real world coordinates. Shifts data within a coordinate system, such as converting feet to meters. Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 61 Rubbersheeting Geometric distortions commonly occur in source maps. They may be introduced by imperfect registration in map compilation, lack of geodetic control in source data, or a variety of other causes. Rubbersheeting corrects flaws through the geometric adjustment of coordinates. Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 62 Edgematching The edgematching process aligns features along the edge of one layer to features of an adjoining layer. The layer with the less accurate features is adjusted, while the adjoining layer is used as the control. Attribute transfer is typically used to copy attributes from a less accurate layer to a more accurate one. Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 63 Spatial Adjustment Example Hamburg Hall Building Drawn in CAD Spatially Adjusted to Aerial Photo Copyright– Kristen S. Kurland, Carnegie Mellon University

GIS 64 Summary Digitizing Overview Digitizing Sources GIS Features Creating and Editing Shapefiles in ArcView Spatial Adjustments Conclusion More to Explore - Tutorial 6 (Introduction to Digitizing) - On-line Help (Advanced Topics) Copyright– Kristen S. Kurland, Carnegie Mellon University