Getting Started with ArcGIS

Module 4 - Raster and Vector data

In this module you will learn how to:● The difference between raster and vector data● Symbolize a raster dataset● Reclassify a raster dataset● Export a raster dataset to vector dataset● Edit vector data● Create contour data● Export into AutoCAD and Google Earth format

11 - Raster data represent geographic features through square or rectangular cells. The cells are laid out in a grid formation. Each cell is typically given a particular value. The values can represent a variety of information for a specific location such as temperature, elevation, etc.

2 - Raster data are often used to display continuous data features. Continuous data represent transitions over land between different possible values, or phenomena that progressively vary over a surface. For instance, raster data are often used for displaying temperature. Since there are no boundaries for where temperatures start and stop, this type of information is well suited to the raster format.

3 - Other examples of raster include air photos, elevation, bathymetry, etc.

4 - Vector data represent the world using points, lines, and polygons. Vectors are well suited to represent discrete data. That is, data that have clear boundaries and do not typically, unlike raster data, represent gradual change over the surface of a geographic area.

5 - Examples of vector data include political boundaries, land parcels, building outlines, etc.

6 - In this module we will examine closely both raster and vector data formats.

7 - For more information on raster and vector formats and the difference in their makeup and use, please see http://resources.arcgis.com/en/help/main/10.2/index.html#//00q8000000n8000000

21 - Start a new map by clicking on the new map icon . Select Blank Map

2 - Do not save your map when prompted.

3 - Navigate to the c:\users\documents\gis_workshop area

4 - Right-click on the landvover.rar* file, select 7-zip and Extract Here. This will uncompress the raster landcover file for the city of Toronto

5 - The file is a Forest and Landcover file and the original can be found here: http://tinyurl.com/torontolandcover6 - You should now notice a new folder called landvover

7 - Using the add data icon add the c:\users\documents\gis_workshop\landvover\toronto_2007_landcover.img

8 - Click on Add

9 - You should now see a map similar to this one

31 - Zoom in and out of your map. Using the Identify tool, click in various areas of the map. You will notice that the only information you will find is a Color Index entry.

2 - You will notice that only the numbers are listed in the Table of Contents as well.

4 - The values for each colour are as follows:

(1) tree canopy, (2) grass/shrub, (3) bare earth, (4) water, (5) buildings, (6) roads, (7) other paved surfaces and (8) agriculture

4 - Double-click on the toronto_2007_landcover.img file in the Table of Contents.

5 - In the Layer Properties window, change the Label for each colour to represent the list above. (hint: double click on the label)6 - Click on OK

41 - In the Table of Contents, click on the red rectangle next to the word, Buildings.2 - In the Symbol Selector window, change the Fill Color to Dark Gray

51 - Using this raster, we will now create a new one subset for only specific types of values. We will now consolidate all our “natural” features into one raster. Our new raster will contain only 4 entries. 1, 2, 3, and 8. These would represent the Tree Canopy, Grass/Shrub, Bare Earth, and Agriculture in our new raster.2 - Click on the ArcToolbox icon3 - Select 3D Analyst Tools, toolbox, select Raster Reclass, and double-click on Reclassify.

4 - Select the toronto_2007_landcover.img raster as your input raster and choose Value as the Reclass field

5 - Change the raster reclassification values as they are entered in the image above.

6 - Create a name and location for the new Output raster (TIF format, .tif) and click the box next to Change missing values to NoData.7 - Click on OK8 - Turn off the original raster in the Table of Contents

61- A new image will soon appear on your screen.

2 - Zoom in and out of your new image.

3 - Repeat the reclassification, but this time, extract only building outlines.

4 - Since buildings are discrete entities, they would best be used in a GIS as vector files. Let’s convert these buildings to a shapefile.5 - Once you have a new raster image containing only buildings, use the Windows menu and select Search

71 - In the search box, type raster to polygon

and click on search

2 - Click on the first entry. This isan ArcTool from

ArcToolBox.ArcToolBox is

a set of toolsused for both

data processingand data analysis.

3 - In the Raster to Polygon window select your new buildings.tif file as your input raster and select an output polygon layer. Make sure to save it as a .shp to save as a shapefile. (eg.buildings.shp)

4 - Click on OK

5 - Your new shapefile should load automatically into your map.

6 - Open the attribute table for your new layer.

7 - You will notice that the attribute table now contains a column populated with the pixel value from our former raster file.

7 - Highlight polygon 3 inthe table and select Zoom To

9 - Close the attribute table

81 - You should now see one highlighted polygon

2 - Using the add data button, select Add Base Map

3 - Select the Topographic basemap and click on Add

4 - Zoom out to a scale of about 1:200

5 - You will notice that our buildings are not exactly where they should be and not formed perfectly. We will now edit some of the features6 - Right-click in the main toolbar andmake sure your Editor toolbar is turned on

91 - Using the Editor toolbar, select Start Editing

2 - Select the Edit tool in the Editor toolbar

3 - Using the Edit tool, click on the vector building and drag it to its correct location

4 - Select the Edit Vertices icon

5 - You will notice howour polygon is now displayed with intersecting points(vertices)

101 - Fit the polygon by deleting, adding, and moving vertices.

- Add a vertex by right-clicking on a line, select Insert Vertex

- Delete a vertex by right-clicking on it and selecting Delete Vertex

- Move a vertex by simply click-dragging it.

2 - When you are done editing. Click on the Editor toolbar and select Stop Editing. 3 - In the Save popupbox, select Yes to saveyour edits.

111 - Open the attribute table for your buildings shapefile

2 - Click on the top-left most icon, and select Add Field…3 - In the Add Field box, giveyour new field the name, BldgName (field names canonly be 8 characters longwith the shapefile format).4 - Select Text as the Type

5 - Click on OK

6 - Using the top-left most icon in the attribute table again, choose Select by Attributes…7 - In the Select by Attributesbox, double-click on the IDfield. 8 - Complete the SQLstatement as below in theselection box. You statementshould now look like the followingSELECT * from buildings WHERE:"ID" = 396843. 9 - Click on Apply

121 - At the bottom of the attribute table, click on the Show selected records icon.

2 - Right-clickon the oneselectedrecord and select Zoom To

3 - You should now be above Robarts Library. If you are not, zoom to it using the zoom in and out tools.

4 - Using the Editor toolbar move and edit the Robarts Library Polygon.

5 - Once you are done with the physical editing, right-click on the Robarts Polygon (anywhere inside the polygon), and select Attributes.

131 - In the BldgName field, enter the text John P. Robarts Library

2 - Hit enter

3 - Select the building to the North East of Robarts using the Edit tool

4 - Drag it onto its proper location.

5 - Add the name Faculty of Information in the BldgName field.

6 - Stop Editing7 - Save your Edits

141 - Double-click on the buildings shapefile in the Table of Contents.

2 - In the Properties window, click on the Labels tab

3 - Select BldgName as the Label Field

4 - Click OK

5 - Your two buildings show now show up with labels.

15 Interpolating from Rasters

1 - Create a new map document2 - Load the two dem files in the folder \gis_workshop\raster\dem\

3 - Using the Identify tool,click on the raster images in multiple locations.You will notice that pixel values increase as you headnorth.

4 - Double-click on image 030m11_0200_demw.dem in the Table of Contents.

5 - Select the Symbology tab and click on Classified

6 - Change the Color ramp to the first option

7 - Click on OK

8 - Repeat 4-6 for the second image, 030m11_0200_deme.dem

16 1 - Your image should now look like this. The colours represent breaks in the elevation.

2 - We will now build contours from these data.

3 - Using ArcToolbox, select the Contour tool under 3D Analyst Tools→ Raster Surface → Contour4 - Select one image at a time as the Input raster5 - Select the name of ashapefile for your first contour file west.shp6 - Select 20 (metres) for your contour intervals.

7 - Click on OK8 - Repeat for the second

image

1 - We will now combine our contours files into 1 file.

2 - Using ArcToolbox, select Data Management Tools→General→Merge

17 3 - In the Merge window, add the two contour files to the Input Datasets area

4 - Provide a location and name for your new shapefile as an Output Dataset 5 - Click on OK

18 Many GIS users are also CAD users. You can easily convert your contours into CAD format.*1 - Right-click on the new shapefile in the Table of Contents2 - Select Data→Export to CAD...

3 - Provide a location and name to your autocad file, click on OK

4 - You should now have a new contour CAD layer loaded into ArcMap

19 We can also export our file to Google Earth Format (KML)