Creating Features in ArcGIS

Workshop #2: Creating Features in ArcGIS

Last week we learned how to add data into ArcMap, and then use that data to map the locations of Lowes and Home Depot stores in the Greater Toronto Area (GTA). But what happens when the data is not completely ready for you to use? In this workshop, we will use the 13 Lowes stores in the GTA to learn how to create and edit features in ArcMap. In doing so, you will also learn how to do one type of trade area delineation – buffers. We will use the data for today again in Workshop 3, so please make sure to save it.

A.    Getting Started

• Log into the remote desktop using your username and password.
• In lab instructions I use >for click, >dc for double click and >rc for right click
• The data for this workshop is stored on the course website in D2L – under Content à Labs à Workshop 2. It is a RAR file called Workshop_2_Data – this means it will have to be extracted/unzipped before we can use it.
• To begin, download the Workshop_2_Data.rar file to the desktop > rc it and extract the files. In the dialogue box that pops up, you will have to chose where you save the files to, as you will need to find them in a few moments.
• REMEMBER: We are using this data again for Workshop 3, so make sure to save!

• Throughout this workshop, you will see references to ‘your workspace’ à this means the folder that you saved all your data to when you downloaded it from D2L.

REMEMBER TO ALWAYS SAVE YOUR WORK!

• Start the ArcGIS program: Start >Program >ArcGIS >ArcMap or >dc the ArcMap icon in the Start menu.

B. Opening a map document

Last week, you added all the layers that you needed manually into ArcMap. This week is slightly different, and is more similar to a ‘real world’ situation where you work on a project over multiple days, possibly on multiple computers. A map document is the file that saves your work, and allows you to pick up where you left off – all the layers that have added and all the visualizations are saved in the map document.

> File > Open > dc in the workspace where you saved the data

• You should see two layers load and be listed in the Table of Contents: GTA_census_tracts – which is a polygon shapefile, and Lowes.txt – which is a textfile that is comma delimited but contains information on the Lowes stores in a useable format for us. NOTE: in some instances, the Lowes.txt file may not appear in the in table of contents. In those cases, you will have to add it using the Add Data tool learned in Workshop 1.
• NOTE: sometimes nothing will appear in the data view, but the layers will be listed in the Table of Contents with a red exclamation point (!) beside them. This means that the layer’s data could not be found. Don’t worry! This is a common issue, especially if you are moving files around between folders or computers. If this happens:
  • Click on the red exclamation point for the Lowes.txt and a dialogue box called Set Data Source will appear. This is similar to the Add Data tool we used last week.
  • Look in your workspaceà you will see the file for Lowes.txt > dc that layer à in ArcMap, the polygons for the census tracts should appear and the exclamation points will be gone.
  • In some cases, you may have to complete the same steps for Lowes.txt

C. Displaying XY Data

C1. Non-Spatial Data

You will have noted that the Lowes data did not appear, and that the file is not a shapefile like the one we used last week. Instead, there is a text (.txt) file extracted from a database. It has a similar attribute table to the shapefiles, but is not currently spatial.

• In the Table of Contents, find the Lowes.txt >rc >select Open
  • You’ll see that the format is very similar to a regular attribute table. Much of the information here is not yet important, but
• Scroll to the far right and you will see two columns – UTME and UTMN. These are the coordinates for each store. Since you are using the UTM projection their units are in metres. UTME is the longitude (the x or east-west coordinate) and UTMN is the latitude (the y or north-south coordinate). These are in text (or string) form, but contain important information to make the records in the table spatial.

C2. Displaying the Data

• In the Table of Contents > rc on Lowes.txt > select Display XY Data…
• In the dialogue box that pops up: for the X-Field select UTME > for the Y-Field select UTMN > Leave the Z-Field as is.
• Make sure that the projected coordinate system is NAD_1983_UTM_Zone_17N
• When you click ok you should see a new point layer appear representing the data from the table called Lowes.txt Events

C3. Saving the Data

Now that we have created this new spatial data file, we need to save it!

• In the Table of Contents > rc on Lowes.txt Events > Data > Export Data…
• Select the file folder to the right of the textbox > save the new file to your workspace as Lowes.shp (make sure the Save as Type is Shapefile)

D. Creating Centroids

D.1. Opening the ArcToolbox and Creating Centroids

(centroids are a point that is located at the centre of a polygon).

• In the main menu, select Geoprocessing > ArcToolbox
• In the dialogue box that pops up à Data Management Tools > Features > Features to Point
• In the dialogue box that appears, there are several things you have to fill out. For all tools, you can look on the right side of the box for a description of what the tool will do.
  • Input Features: GTA_Census_Tracts
  • Output Features: press the file folder to the right, and save as GTA_Census_Tracts_centroid
  • Check the box labelled Inside (optional) à this makes sure that the centroid point that is created is located within the polygon feature. Sometimes if a polygon is a weird shape, the centroid could be calculated to be outside of its boundaries.
  • You will see a new layer appear on the map as points, and the corresponding layer appear in the Table of Contents (GTA_Census_Tracts_centroid). If you open the attribute table, you will see that all the information from the polygon layer has automatically been transferred into the point shapefile.

D. Creating Buffers

• In ArcToolbox à Analysis Tools > Proximity > Buffer
  • Input Features: select Lowes from the dropdown list
  • Output Feature class: press the file folder to the right, and save as Lowes_Buffer_15km to your workspace.
  • Linear Unit: you can either enter 15000 and leave the units as meters or enter 15 and change the units to km à This is the radius of the buffer.
  • Keep the remaining options in their default: one feature to keep in mind is Dissolve Type. In sort, it determines if the buffers that are created are separate or joined together if they overlap
  • You will see a new layer appear on the map as a polygon, and the corresponding layer appear in the Table of Contents (Lowes_Buffer_15km). If you open the attribute table, you will see that all the information from the point file has automatically been transferred into the polygon shapefile.

When you have reached this point, you need to make a map with the buffers, census tracts, and store locations. See Workshop 1 for a refresher on key map elements. Export or screenshot the completed map and upload it to D2L in Workshop 2 to get the completion mark.