Heads up Digitizing v 9.3

Transcription

1 Heads up Digitizing v 9.3 Created by Vince DiNoto Vince.dinoto@kctcs.edu Table of Contents Prerequisite... 2 Getting Started... 2 ArcCatalog ArcMap Projection... 4 Attribute Table... 6 Editor... 7 Table of Figures Index... 12

2 Prerequisite It is assumed that those attempting this module have loaded image files onto a map and that the geography of the map has been aligned with an appropriate basemap 2 or shapefile 4 and projected. If the image file is not appropriate aligned you should first do the module on Georeferencing. Getting Started In this module you will take features that are on an image and convert them into a vector object (shapefile). The features can be points, lines or polygons. This will be accomplished by manual digitalization of the feature, using a mouse. A digitizing pad can be used but it is not required to complete this module. To begin this module you need to have one or more basemap layers loaded into ArcMap and they need to have a geographical projection. These base layers can be shapefiles or an online service. You need to have one or more image files loaded in ArcMap which might be an aerial image or a paper map that has been scanned. The image file(s) needs to be georeferenced to the basemap layer, i.e. that the features on the image and base layer align. Next you will create an empty layer file in ArcCatalog. If you need additional information beyond what is covered in this module on ArcCatalog please refer to that module. ArcCatalog You can open ArcCatalog either directly from program files or from within ArcMap. In Figure 1: ArcCatalog you can see the file structure in the Kentucky Polygon folder. Figure 1: ArcCatalog

3 You can either left click on File on the menu bar and select New or right click on a file folder and select New. Select the operation you wish to complete, for our case we want to create a new Shapefile. Figure 2: New Shapefile Once you provide the name of the new shapefile you will need to tell the program the type of shapefile that you wish to create, i.e. point, line, polygon, etc. The shapefile that will be created will be an empty shapefile of the particular type specified. You can create multiple files for different items to be Figure 3: New Shapefile Type digitized from your map. You can also add attribute columns to the shapefile from inside ArcMap.

4 ArcMap Load the newly created shapefile(s) onto you basemap, since there is no data in the shapefiles nothing new will be displayed. Projection The file will also not have a projection since unless it was specified in the creation of the shapefile. A projection is important and can be edited from the toolbox. Open the Toolbox and select Data Management Tools. Under Data Management Tools select Projections and Transformations and then select Define Projection. The type of projection will need to be defined and should match the image file. Figure 4: Toolbox, Projections A new window will open and you must select the layer and the coordinate system to be used. In Figure 5: Selecting shapefile and Coordinate System, the file has been selected and next click on the second icon to open the coordinate system window. Figure 5: Selecting shapefile and Coordinate System

5 Figure 6: Selecting Coordinate System We have selected to import a coordinate system and we are going to import the one used by the image file.

6 Figure 7: Competed Coordinate System selection The selected coordinate system is displayed in Figure 7: Competed Coordinate System selection. Attribute Table Figure 8: Attribute Table Add Field

7 Open the attribute table of the newly created shapefile and add additional fields to the shapefile. Figure 9: Field Name Note this must be done with the editor turned off. The new field is called Descriptio note you cannot use spaces in the name and you are limited to the number of characters in the name. You cannot populate the new fields added from the attribute table view. Editor Once you have added the appropriate fields you will want to turn on the editor (start editing). The editor can be found under view under toolbars. The editor is a toolbar so it can be either Figure 10: Editor Toolbar docked or floating. The first button in the editor is a pull down and you need to click start editor. Once the editor has been started you will need to select what is to be edited. At this point you will select one of your newly created shapefiles. Remember if you want the data to be points it must be placed in the shapefile that was created for point same is true with lines and polygons. Select the data you wish to digitize. For example if you have an aerial view of fields which have crops located within them, you will want to have a polygon shapefile to Figure 11: Start Editing add the data. Therefore you would click at every corner of the field. When you get to the last corner you would double click to complete the polygon. It will appear as the selected polygon until you begin creating the next. Before creating the next you may want to add information about the field in the attribute table, like the crop that is being grown in the field. You would continue the process, when one field is touching another you will want to use the snap feature of the editor so that corners are touching each other. Another example, let s assume you are looking at the Gettysburg Battlefield on historical maps created for the troop positions at 4 PM on July 2, 1863

8 (the second day of the battle). What you want to digitize is the position of the different regiments on the field of battle. You want to have a designation for Union troops and different one for Confederate soldiers. They could be in one or two line shapefiles. You would also need to have fields that designate the regiment, brigade, division and corps they belonged to so that they can be queried when actually using the map, you may also want to include the officer in charge. Let s assume we make one shapefile for Union and one for Confederate troops. We would start the editor and click on the line of a single regiment, it might just be two points or it could be multiple points depending on their line of battle. You would complete the placement of the regiments and then fill in the appropriate fields in the attribute table. Figure 12: Digitizing For our example we will be editing a topographic sheet from Jeffersonville, IN. We have started the editor and select the target file test. Next select the pencil tool. We are going to digitize new areas on the topo sheet that are in purple on the map. The file test is a polygon shapefile. We will click on the map with the mouse every time direction changes in our target area. In Figure 12: Digitizing you can see to light blue areas which have been digitized on the Jeffersonville topographic sheet. If you want to add a name to these areas you will need to open the attribute table, and since the editor is turned you

9 can edit items in the table. Figure 13: Editing Attribute Table In Figure 13: Editing Attribute Table, you can see I have added the name Meadows, since this is the Meadows area of Jeffersonville. You can close or minimize the attribute table and go back to digitizing.

10 To insure that surface connect seamless there is also a snap feature which is located under the editor pull down. Clicking on Snapping will open a new window, which will give multiple ways in which you can control the snap feature. You cannot snap to items on a raster, but can to your editing shapefile or to other shapefiles. Figure 15: Snap WIndow Figure 14: Snap You can under the editor pull down, save the data and continue to edit or stop the editor and save the data. It is recommend that you save often so that data is not accidently lost. Once the process is completed you will have a vector shapefile that can be managed like any other shapefile, based upon a raster image. Figure 16: Saving Edits

11 Table of Figures Figure 1: ArcCatalog... Figure 2: New Shapefile... 3 Figure 3: New Shapefile Type... 3 Figure 4: Toolbox Figure 5: Selecting shapefile Figure 6: Selecting Coordinate System... 5 Figure 7: Competed Coordinate System selection... 6 Figure 8: Attribute Table - Add Field... 6 Figure 9: Field Name... 7 Figure 10: Editor Toolbar... 7 Figure 11: Start Editing... 7 Figure 12: Digitizing... 8 Figure 13: Editing Attribute Table... 9 Figure 14: Snap Figure 15: Snap WIndow Figure 16: Saving Edits... 10

12 Index aerial view, 7 ArcCatalog, 1, 2, 11 ArcMap, 1, 2, 3, 4 attribute, 3, 6, 7, 8, 9 basemap, 2, 4 coordinate system, 4, 5, 6 Data Management Tools, 4 Define Projection, 4 editor, 7, 8, 10 Georeferencing, 2 Gettysburg Battlefield, 7 historical maps, 7 Jeffersonville, 8, 9 line, 3, 8 point, 3, 7 polygon, 3, 7, 8 projected, 2 projection, 2, 4 Projections and Transformations, 4 queried, 8 shapefile, 2, 3, 4, 6, 7, 8, 10, 11 snap feature, 7, 10 Toolbox, 4, 11 topographic sheet, 8 vector object, 2

13 2, Projections... 4 and Coordinate System... 4