Digitizing in ArcMap

 



INTRODUCTION

         This lab will involve downloading a jpeg file from the web and importing it into ArcMap.

         A shapefile is created, and this shapefile is used to sketch the features on the map into a polygon layer.

         Once the shapefile has been created, attributes will be added to the associated table. Data for the attribute table is provided in this exercise.

         A layout will be created and exported as drawmap.pdf



GETTING STARTED

         Download http://www.hort.purdue.edu/newcrop/cropmap/nebraska/maps/NEeco3.jpg by right clicking on the link and choosing Save Target as and save the file as NEeco3.jpg.

         Once you have the jpg saved, go into ArcCatalog to check out the metadata by double clicking on it.  You will notice that this file is in raster format and has three bands.



IMPORTING

         Start ArcMap.  Choose to start using ArcMap with a new empty map, then click OK.

         Add NEeco3jpg to your view.  To do this, open ArcCatalog and navigate to NEeco3jpg.  Click on NEeco3jpg and drag it into your ArcMap view.   

         Your image is now part of your view window's table of contents. You must click on the box in the view window's table of contents to make the theme active and view your image.

         At this time, save your project.



DIGITIZING

         First, a new shapefile will need to be created.  Select a folder in the Catalog tree in ArcCatalog where you want to store your new shapefile.  Click File - New - Shapefile Click in the Name text box and type Ecoregions. Then under Feature type, select polygon.  Click Edit to define the shapefile's coordinate system.  In the Spatial Reference Properties dialog box, click Select and choose Projected Coordinate Systems - Continental - North America - USA Contiguous Albers Equal Area Conic then click Add.  Click OK twice.  Ecoregions should now be in the Catalog tree.

        Next you will have to add the new shapefile to your view in ArcMap.  Click the Add Data button.  Navigate to Ecoregions, then click Add

         In order to make changes to Ecoregions, the Editor toolbar will need to be added under View - Toolbars - Editor

         Click the Editor menu and click Start Editing.  The Editor toolbar is now active.

         A message window might open. Click Start Editing.

         To create a new feature in ArcMap, you need to first create an edit sketch.  A sketch is composed of vertices (the points at which the sketch changes directions such as corners) and segments (the lines that connect the vertices).  You will create a sketch using the sketch construction tools located on the tool palette.  Select Create New Feature under Task and select the Sketch tool (looks like a pencil) from the Editor Toolbar.  Using this tool, you will trace the outline of Nebraska.  To begin digitizing, click once to make a vertex and then following the polygon lines click once at each change in direction.  When you are finished sketching Nebraska, double-click to finish drawing the feature.

         At this time, you will want to save your edits.  Under the Editor dropdown menu in the Editor toolbar, select Save Edits

         Now that you have the outline of Nebraska, you need to create individual polygons for each ecoregion. To see the the lines on the image which lays behind your new Ecoregions layer, make the colored area invisible. Do so by clicking on the color pad under the layer and choose Hollow. In the Task pull-down menu select Cut Polygon Features.  Now you will use the tool that looks like a pencil again to cut and draw vertices for each polygon.  Click out of Nebraska to start the first point and then begin drawing the line that will cut the polygon of Nebraska.  Make sure to go outside of Nebraska to finish the line. Again close you line by double-clicking.  Do this for each polygon.  

         When you are finished with each polygon, click on the Editor pull-down menu and select Save Edits.

         You now have a shapefile showing different ecoregions.



ADDING ATTRIBUTES

         Right click on Ecoregions and Select Open Attribute Table.

         First you will have to change the IDs of the polygons.  Number 25 will have an ID of 1, number 27 will have 2, 42 will have 3, the two polygons in 43 will have 4, the two 44s will have 5, and 47 will have 6.   

         To change the IDs, click on the far left of the row you want to change and the row will become highlighted.  If you look at the map you can see that the appropriate polygon is highlighted.  Then, double click in the ID box that you want to change and make the appropriate changes.

         At this time, go to the Editor pull-down menu and Save Edits.  Then under the Editor pull-down menu Stop Editing

         Click Options in the Attributes of Ecoregions.  Then select Add Field.  You will name the Field Name Type, the Field Type will be text and leave the field properties the same, then click OK.    

         Under the Editor pull-down menu select Start Editing

         Under the column type, you will type the appropriate name for each ecoregion.  ID 1 will be Western High Plains, 2 - Central Great Plains, 3 - Northwestern Glaciated Plains, 4 - Northwestern Great Plains, 5 - Nebraska Sand Hills, 6 - Western Corn Belt Plains. 

         Go ahead and save your edits at this time, then stop editing.   

         Now you can turn off  or  remove NEeco3.jpg.

         Right click on Ecoregions, select Properties then click on the Symbology tab. Click on Categories in the left column, then choose Unique Values Uncheck the symbol in the bottom box.  Then choose Type under Value Field.  Click the Add All Values button on the bottom to add all of the ecoregion types.  Click OK

         Now you will want to label one polygon from each ecoregion.  Right click on Ecoregions, select Properties, then click the Labels tab.  Check Label Features in this layer and under Label Field, choose Type.  Click OK.  To convert the labels to annotation so you can make changes easier, right click on Ecoregions and select Convert labels to annotation.  Check Store in Map and click Convert

         There only needs to be one label for each ecoregion, so select and delete the two extra labels.  You will probably also want to change the font and make the labels bold (multiple selection with Shift key). 

         Make sure to save your project often.



CREATING LAYOUTS

         Go to View - Layout View.  

         Go to File – Page Setup and make sure Landscape is selected for Map Size and Printer Setup. 

         You will need to appropriately add a title, legend, neat line, scale bar, and name and date the map.  You will add a title, name and date by using A in the draw menu and can change the font in the draw menu also.  To add a scale bar, neat line and legend, go to Insert on the main menu. 

         Save your work.

         Under the File pull-down menu, click on Export Map.

         From the Save as Type box, select PDF.

         Name your layout drawmap.pdf and click OK to save.


Page created by Jamie Cook - September 2001, updated by Kristie Raymond – September 2002, further updated by Eva Grund – August 2004