NSF DUE ; Laura Johnson Wen Andrews

NSF DUE ; GeoTEd Partners

NSF DUE ; Module Outline Digitizing Georeferencing Using CAD Data

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What is Digitizing? The process of making paper (analog) maps digital Georeferencing Registered to the correct part of the map Projection/Coordinate system defined Defining attributes Populating attribute fields

NSF DUE ; Digitizing methods Create new Feature Class (point, line, or polygon) to store new digital features Use a digitizing tablet and puck to digitally “trace” paper map “Antiquated method Scan a paper map Register (georeference) new image Create points, lines, or polygons using scanned image and remostely sensed imagery for reference

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What is georeferencing? Sometimes called “rubber sheeting” Rectifying or registering an image to the correct geographic location CAD data Scanned map Aerial photos Can be a time-consuming process Auto Georeferencing available for datasets that are very similar Match points on the scanned picture to known points on the map

NSF DUE ; Georeferencing in ArcGIS Start with a map with the data you will match “to” Add the raster dataset you want to georeference Assign control points Matching a point on the target dataset to the base data already on the map Continue until the datasets are lined up as well as possible Source: ArcGIS 10.1 help

NSF DUE ; Georeferencing in ArcGIS How many control points? Best to spread out to the corners of the image Check the links table RMSE, lower is better Can add and delete points while checking the table Transformation Permanent warping of the target dataset Not always necessary but can help reshape the data

NSF DUE ; Transformation types Source: ArcGIS 10.1 help

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What is CAD Data? Vector files Common applications Surveying Civil Engineering Architecture Landscape architecture File types DWG DGN

NSF DUE ; Importing CAD Datasets Can be added directly from ArcCatalog or the Add Data button Typically lots of features in one dataset Geometry, text, and symbols Definition Queries can help to filter data Usually need to be projected Can also be imported to a Geodatabase

NSF DUE ; Questions?