1Geoprocessing and Spatial Data Editing in ArcGIS I. Geoprocessing – a set of software functions used to manipulate and transform spatial data (single layers or multiple sets of layers), to create new information. Manipulation of features classes and attribute tables to extract new information. a. Map Overlay functions – combining layers to create single output i. Extraction Functions - Layer Attributes Not Combined – features are separated from a larger group of features within a map layer 1. Clip – a cookie cutter function that truncates the features of one file based upon the outline of another. a. Layers to be clipped – points, lines or polygons i. Clip a subset of a map theme ii. For example, you may want to select a county boundary from your counties theme to extract the roads from your roads theme to create a new theme containing a smaller number of roads. b. Clipping (cutter) Layer – must be polygon i. Features inside the clip boundary will be preserved, all those outside are removed ii. Attributes of the clipped layer are preserved as in the original, only clipped to the preserved features 2. Erase – opposite of clip, all information outside of the operational polygon are preserved, and the interior features are erased. a. Attributes of the erased layer are preserved in their original composition. ii. Intersection Functions - Layer Attributes Combined 1. Use the Intersect process when you want to integrate two spatial data sets while preserving only those features falling within the spatial extent common to both themes. a. For example, suppose you are a builder and want to build a retirement center within the city boundaries. 2. Intersect – merges attributes between layers, points-lines-polygons 3. Union – combines two polygon layers, keeping all areas and merging attributes iii. Dissolve – combines and dissolves polygons together based on common attributes 1. For example, Dissolve could be used to create a theme showing sales regions by salesperson where each salesperson is responsible for several counties. iv. Buffer – creates new polygons that form a zone or region, with a known radius, about map features (points or lines).21. Undissolved buffers –separate polygons 2. Dissolved buffers – merged polygons v. Append and Merge – tools that merge “edges” of adjoing layers with identically matching polygons and attributes. Result takes individual map mosaics and combines them into one output layer. 1. Merge a. Combines two shape files into 1 b. For example, you may want to merge or append highway data delivered as a series of tiles. Merge allows you to append the data while maintaining the attributes contained in whichever shapefile you select. b. ArcGIS Tools for Geoprocessing i. ArcToolbox – geoprocessing tools take an “input file”, modify it, and create a new “output file” via geoprocessing transformation. 1. command line – allows scripting of tool menus 2. model builder – provides graphic visualization of tools and their resultant outputs 3. scripting – user may customize the tool with options and special function ii. Coordinate System Management 1. Arc geoprocessing tools will default such that the new output files will have the same projection as the input files 2. Environment Settings – may create different projections for the output files (essentially geoprocessing and re-projecting at the same time). iii. Updating feature measurements 1. geoprocessing and resulting output attribute tables will automatically be updated with resprect to areas, lengths, and perimeters of map features a. e.g. clipped polygons will have their area fields updated upon modification via geoprocessing. II. Quick Guide to ArcTool Box and Geoprocessing Functions Tab Functions – place the arctool box menu on your workspace The toolbox menu has three tabs: Favorites – list of all tools and pull down menus Index – search by key words (locate – finds the tool) Search – search by key words (finds tool by key word) a. Clip tool ArcTool Box- Analysis Tools – Extract - Clip b. Erase tool ArcTool Box – Analysis Tools – Overlay - Erase c. Intersect tool ArcTool Box – Analysis Tools – Overlay – Intersect3d. Union tool ArcTool Box - Analysis Tools – Overlay - Union e. Dissolve tool Arc Tool Box – Data Management Tools – Generalization - Dissolve f. Buffer tool ArcTool Box - Analysis Tools – Proximity - Buffer g. Append tool Arc Tool Box – Data Management Tools-General – Append h. Merge tool Arc Tool Box – Data Management Tools- General – Merge _________________________________________________________________________________________ In-Class Exercise - Geoprocessing Functions with ArcView Task 1 - Getting the Tutorial Data and creating projection definition files - create a new class subfolder on your H:\drive = “geoprocessing” - visit class website, go to lab data section, download and unzip "geoprocessing tutorial data" to your network drive (geoprdata.zip), extract the data to a new folder - Once you’ve extracted all the shape files, check to see if there are existing *.prj projection files for each shape in the tutorial dataset. If not, use the Project-Define tool in Arctool Box to create projection files for all of your data. They are in UTM Zone10 N, NAD1927 CONUS, meters. -Add the surfgeo.shp and streams.shp to the view, check out the data (projection: UTM zone10N, surficial geology and stream tributaries for a portion of the Luckiamute watershed) Task 2 - Clipping Goal: to use a "clip" file (a cookie cutter) to cut out a subset of the streams.shp, and create a new shape theme - add streams.shp and clipbox.shp to the view; Using the symbol / properties editor, make the clipbox.shp a clear and open polygon with no fill color -you will be using the clip box as a cookie cutter to create a subset of streams and save them to a new shape file ArcTool Box- Analysis Tools – Extract - Clip 1)select input theme to select = streams.shp 2)select a polygon overlay theme = clipbox.shp 3) specify output file: browse to your network drive and save the new shape file as "strmclip.shp" Add the new strmclip.shp is added to the table of contents, activate it and check out what happened4-Turn off the streams.shp, go to layout and print out your view with the clip box and strmclip.shp (remember to put your