Geog. 250 GIS Survey

Title: Instructions for building a feature (vector) map from and image (raster) theme.

Purpose: GIS – Map Building from image data

For this assignment we will be using an aerial photograph of the WWU campus to build ArcView "shapefiles." A shapefile (also known as a feature data theme) is a set of computer files that stores the coordinates of a point, line, or polygon feature. We will be using a process known as "on screen digitizing" to convert features in the photo from a raster format (scanned images) to a vector format (the format Arc View uses). Once the shapefile has been created you can attach "attributes" to the shapefile. Attributes describe the feature, things like name, use, size, or any other information you might feel is important to the feature (building attributes tables will not be required for this assignment).

Procedure: (it looks complicated but it’s really not!)

1. Log on to the computer.

2. Create a new folder in C:\temp

1. Go to START and then NT Explorer (up near the top)
2. Double click on the "temp" folder in the C drive
3. Move the cursor to the right hand window then
4. Click the right hand mouse button and select "new" and then "folder" (up near the top)
5. Type a new name for your folder (use your last name and first initial) and press the RETURN key.
6. Fold NT Explorer down to your button bar.

3. Start up ArcView

1. Go to START and then Esri – ArcView 3.3 – ArcView GIS Version 3.3 (or current version)
2. Create a "blank project" and click "ok"
3. Double click on the "views" icon to open a new view (view 1)
4. Make sure that you have activated the Jpeg extension or the file will not load into ArcView.

4. Add the WWU Campus aerial photo theme (image data source)

1. Click the "add theme" button (plus sign icon in the top left screen) – the "add theme" window pops up
2. Under "drives" select the "Echo\saldata" drive – this is the J drive on most machines. If there is no Echo\saldata drive you will have to "map network drives" in NT Explorer. If you are floundering at this point, ask the Instructor and be sure to take good notes on how to do this in the future.
3. Double click on the folder called "data_bham"
4. Double click on the folder called "data_airphoto" then "1997_color"  – make sure in ArcView that the "data source types" are set to "image data source" – this tells ArcView to look for raster based images.
5. Double click on the image titled "r380331.jpg"
6. Click in the little box for the R380331.jpg theme to make the aerial photo visible

5. Creating ArcView shapefiles:

1. Zoom into the south campus area (Artzen Hall, ES Building, soccer fields, etc.) or any other location in the r8331.tif image you want to map.
2. On Screen Digitizing – this is easy and in this exercise is basically just tracing around a feature in the aerial photo!

• Find a building (or any other feature you want to digitize). You may digitize any point (tree), line (road), or polygon (building) feature you want.
• Start digitizing by selecting one of the "draw tools". These are the icons located in the bottom group of icons. Draw tools are to the far right. By default the "point" tool will be the only tool to display. To chose lines or polygons, click on the point tool and hold the mouse button down - all the draw tools display in a drop down menu. We will be working with the point tool (#1), the line tool (the squiggly, not straight line, #3), and the polygon tool (#6).
• Select the appropriate draw tool for the feature you are digitizing:.

• For point features, select the point tool and click on the point feature in the photo.
• For line features,
  • select the line tool and
  • click on the starting point of the line drag the pointer and single
  • click wherever you want the line to bend (vertex).
  • Double click where you want the line to end.
• For polygon features,
  • select the polygon tool and
  • click where you want to begin,
  • click again to make a vertex in the polygon,
  • double click to close the polygon.

6. Active Graphics (points, lines, or polygons that you have drawn)

After the point, line or polygon has been drawn, little black squares (called handles) appear around the object. This indicates that what you have drawn is an active "graphic." You can always make a graphic active by clicking on it with the pointer tool (the black arrow icon on the far left), not the draw tool! You can make more than one graphic active by clicking one graphic and then while holding the SHIFT key, click on another graphic (make sure that both graphics are the same type. Active graphics can be deleted by pressing the DELETE key. Note: The graphic(s) must be active to convert it to a shape file!

7. Copy a Graphic

• Once the desired graphic(s) is(are) active, go to the "edit" menu and select "copy graphic."
• You can also copy an active graphic by pressing CTRL+C.

8. Create and Name a New Theme (new data layer)

• From the "view" menu select "New Theme" – You will be prompted to tell the computer what type of feature your copied graphic is (point, line, or polygon).
• You will then be prompted for the file name and location (choose a descriptive name like "tree" or "Parkhall").
• Be sure to save the new theme into your C:\temp\new folder (double click on your folder).
• In the view your new theme will appear. Notice the dotted box on the theme – this means that it is ready to be edited.

9. Paste your Digitized data (feature) into your New Theme

• Paste your copied graphic into the new theme by selecting "edit/paste" from the menu
• or by simply pressing CTRL+V.

10. Save your New Theme then Clear Selected Features

• From the "theme" menu select "stop editing,"
• and then do "File/save".

Your traced graphic is now a shape file and can be edited! However, before doing this under the

• Theme menu us the Clear Selected Features command (prior to this the feature will be yellow and not fully respond to the legend editor).

11. Improving your New Theme

You can now edit the color, line thickness, fill properties, size, etc. of your theme by double clicking on colored box in the Table of Contents and opening the "legend editor." and "pallet manager"

12. Adding Text Labels

• Create a titles for your shape files by clicking on the "text" icon (right next to the draw tools).
• Click in the view where you want the test,
• and the "text properties" box comes up. Type a label and click OK.

13. Keeping Things Simple and Correct

Shape files (the place and way you save your New Theme) can have only Points, Lines, or Polygons, you CANNOT COMBINE such as points with lines. Further, since you are just starting, let's keep things simple, make each digitized feature a separate shapefile, all with different names! So Arntzen Hall could be one file and different from Parks Hall. This is not required if both are geometrically the same (here polygons), but it will save a lot of frustration while you are just learning screen digitizing.

14. Make a Map

When you are done creating shape files, use the Layout command under the View menu to create a really nice output. However, if you have problems with that level of expertise, then simply Print out your results under the File menu pull down list.

 

Originator:  P. Buckley  -- patrick@cc.wwu.edu
Updated:  Apr. 29, 2004