Site a new hospital

Open and save a map

First, you'll open a map, save a copy, and explore the layers.

  1. Open the Site a new hospital map on ArcGIS Online.

    A map with four layers and a basemap appears.

    Map of Loudoun County

  2. At the top of the page, click Sign In and sign in to your ArcGIS account.
    Note:

    If you don't have an organizational account, you can sign up for an ArcGIS free trial.

  3. On the ribbon, click Save and choose Save As.

    Save As option

  4. In the Save Map window, for Title, type Site a new hospital followed by your name or initials.
  5. For Tags, type teachgis, site selection, Loudoun County, hospital.
  6. For Summary, type Possible locations for a new hospital in Loudoun County, VA.

    Save Map window

  7. Click Save Map.

    A copy of the map is saved to your ArcGIS account.

  8. Below the ribbon, click Content.

    You'll investigate the data you'll use. The four layers include the location of the current main hospital, the main roads, the urban areas, and the boundary of the county.

  9. Click the check box next to each layer to turn it off and click it again to turn it on.

Create a buffer around urban areas

Next, you'll create the data to address the first criterion (within two miles of urban areas). You'll create a layer with a two-mile buffer around the urban areas. A buffer is a zone around one or more map features measured in units of distance or time. The Create Buffer tool is one of the proximity tools that analyze map data based on how close or far away a second feature is.

  1. Point to the Urban Areas layer and click the Perform Analysis button.

    Perform Analysis button

  2. Click Use Proximity.

    Use Proximity option

  3. Click Create Buffers.

    Create Buffers tool

  4. For Choose layer containing feature to buffer, confirm that Urban Areas is selected.
  5. For Enter buffer size, choose Distance, type 2, and choose Miles.
  6. Expand Options.

    You'll indicate how you want overlapping buffers to be handled. You'll choose to merge any overlapping areas into one feature.

  7. For Buffer type, choose Dissolve.

    You'll indicate whether you want to keep the features, in this case, the urban areas, in the resulting buffer. You'll choose not to keep them.

  8. For Area of input polygons in buffer polygons, choose Exclude.

    Create Buffers tool parameters

  9. For Result layer name, type BufUrbanAreas2Mi followed by your name or initials.
  10. Uncheck Use current map extent.

    Result layer name parameter

  11. Click Run Analysis.

    After a few moments, the new layer is added to the top of the Contents pane and drawn on the map. The blue areas show the two-mile buffer around the urban areas.

    Map with buffered urban areas

  12. On the ribbon, click Save and choose Save.

Create drive-time areas around the main hospital

To address the second criterion (more than a 20-minute car ride from the current hospital), you'll create drive-time areas. A drive-time area is the area that can be reached within a specified travel time or travel distance along a street network based on travel mode. Travel mode refers to different ways of moving along a street, such as driving a car, riding a bike, taking a bus, or walking.

The Create Drive-Time Areas tool is a proximity tool. Like the Create Buffer tool, it analyzes map data based on how close or far away features are, but it does so along a street network.

  1. For the Main Hospital layer, click Perform Analysis.
  2. Click Use Proximity.
  3. Click Create Drive-Time Areas.

    Create Drive-Time Areas tool

  4. For Choose point layer to calculate drive-time areas around, confirm that Main Hospital is selected.
  5. For Measure, confirm that Driving Time is selected, type 20, and choose Minutes.

    You want to identify locations from which county residents can access the hospital within a 20-minute drive.

  6. For Travel direction, choose Towards Facility.

    Create Drive-Time Areas parameters

    You'll indicate how you want areas from different points to be handled. You'll choose to dissolve any overlapping areas into one feature.

  7. For Areas from different points, choose Dissolve.
  8. For Result layer name, type Drive20MinHospital followed by your name or initials.
  9. Uncheck Use current map extent.

    Areas from different points and Result layer name parameters

  10. Click Run Analysis.

    ArcGIS Online uses a detailed up-to-date road network to perform the analysis. It does not use the main roads layer you see on the map.

    After a few moments, the new layer is added to the top of the Contents pane and drawn on the map. The dark purple shows the area from which people can drive to the hospital in 20 minutes or less.

    Drive-time areas map

  11. Save your map.

Create a buffer around main roads

To address the third criterion (within one mile of main roads), you'll create a buffer around the main roads.

  1. For the Roads layer, click Perform Analysis.
  2. Click Use Proximity and click Create Buffers.
  3. For Choose layer containing features to buffer, confirm Roads is selected.
  4. For Enter buffer size, confirm Distance, 1, and Miles are selected.

    Create Buffers parameters

  5. Under Enter buffer size, expand Options.
  6. For Buffer type, choose Dissolve. Confirm Side type is set to Around and End type is set to Round.
  7. For Result layer name, type BufRoads1Mi followed by your name or initials.
  8. Uncheck Use current map extent.

    Buffer type options

  9. Click Run Analysis.

    After a few moments, the new layer is added to the top of the Contents pane and drawn on the map.

    Road buffers map

    The roads buffer layer and the urban areas buffer layer are hard to distinguish, since they are similar shades of blue. To make them easier to discern, you'll change the symbol for the roads buffer layer.

  10. For the BufRoads1Mi layer, click the Change Style button.

    Change Style button

  11. For Choose an attribute to show, confirm Show location only is selected.
  12. For Select a drawing style, click Options.

    Location (Single symbol) Options button

  13. Click Symbols.

    Symbols button

  14. For Fill, choose dark gray (#858585).
  15. For Transparency, set the slider to 25 percent.

    Gray fill color

  16. For Outline, choose black (#1A1A1A). Confirm that Line Width is set to 1.33 px.

    Black outline color

  17. Click OK.
  18. Click OK. Click Done.

    The dark gray shows the area within one mile of the main roads.

    Symbolized road buffers map

  19. Save your map.

Combine buffers and drive-time areas

Next, you'll combine the layers you created to identify only those areas that meet the three criteria. You'll use the data management overlay layer tools; these tools work on two layers at a time, so you'll use them multiple times.

First, you'll combine the buffered urban area layer and the 20-minute drive-time layer.

  1. In the Contents pane, turn off the BufRoads1Mi, Main Hospital, Roads, and Urban Areas layers.

    Urban area buffers and drive-time areas map

    Review your map and consider the areas that are within two miles of urban areas and are more than a 20-minute car ride from the main hospital. How would you describe in words how to get only those areas? You might say you want to subtract the drive-time area from the buffered urban areas. That's what the Erase tool does.

  2. For the BufUrbanAreas2Mi layer, click the Perform Analysis button.
  3. Click Manage Data and choose Overlay Layers.

    Overlay Layers tool

  4. For Choose input layer, confirm BufUrbanAreas2Mi is selected.
  5. For Choose overlay layer, choose Drive20MinHospital.

    The Erase tool returns the areas in the input layer (BufUrbanAreas2Mi) that do not overlap the areas in the overlay layer (Drive20MinHospital). The result is the areas of the BufUrbanAreas2Mi layer that are outside the Drive20MinHospital layer drive-time areas.

  6. For Choose overlay method, choose Erase.
  7. For Result layer name, type Suitable1 followed by your name or initials.
  8. Uncheck Use current map extent.

    Overlay Layers parameters

  9. Click Run Analysis.

    After a few moments, the new layer is added to the top of the Contents pane and drawn on the map.

    First suitability result layer on map

  10. Turn off Drive20MinHospital and BufUrbanAreas2Mi.

    Other layers turned off on the map

    The Suitable1 layer includes areas within two miles of urban areas but does not include areas within a 20-minute car ride to the main hospital.

  11. Save your map.

Create a layer that addresses all criteria

Next, you'll combine the result of the last step, the Suitable1 layer, and the buffered roads layer to create a layer that addresses all three criteria.

  1. In the Contents pane, turn on the BuffRoads1Mi layer.

    Buffered roads and suitable areas on the map

  2. For the Suitable1 layer, click the Perform Analysis button.
  3. Click Manage Data and choose Overlay Layers.
  4. For Choose input layer, confirm that Suitable1 is selected.
  5. For Choose overlay layer, choose BufRoads1Mi.

    You're looking for locations that are in both the Suitable1 layer and the BufRoads1Mi layer. That's how the Intersect tool works; it returns the areas the two layers have in common.

  6. For Choose overlay method, choose Intersect.
  7. For Result layer name, type Suitable2 followed by your name or initials.
  8. Uncheck Use current map extent.

    Overlay Layers parameters

  9. Click Run Analysis.

    After a few moments, the layer is created and added to the top of the Contents pane.

    Second suitability layer on the map

  10. Turn off Suitable1 and BufRoads1Mi.

    Map showing only the second suitability layer

  11. Save the map.

    The areas in the Suitable2 layer meet all three requirements for locating the new hospital. Is there another criterion, one that was not explicitly stated, that has not been addressed? Look at the boundary of Loudoun County. Some of the areas are not in Loudoun County. You'll address that issue next.

Find suitable areas in the study area

Finally, you'll perform one last analysis to find areas that meet the three stated criteria and are within Loudoun County.

  1. For the Suitable2 layer, click the Perform Analysis button.
  2. Click Manage Data and choose Overlay Layers.
  3. For Choose input layer, confirm that Suitable2 is selected.
  4. For Choose overlay layer, choose Loudoun County.

    You're looking for locations that are in the Suitable2 layer and in the Loudoun County layer.

  5. For Choose overlay method, choose Intersect.
  6. For Result layer name, type Suitable3 followed by your name or initials.
  7. Uncheck Use current map extent.

    Overlay Layers parameters

  8. Click Run Analysis.

    After a few moments, the layer is created and added to the top of the Contents pane.

  9. In the Contents pane, turn off the Suitable2 layer.

    Final result layer on map

  10. Save your map.

    The Suitable3 layer now meets the provided criteria, as well as the one that was implied, that all the locations be in Loudoun County.

In this lesson, you created data layers using proximity and data management tools. You created buffers and drive-time areas to identify areas within a time or a distance from map features. You then combined these new layers, and the boundary of Loudoun County, using overlay layer tools to create a layer that includes areas that meet the spatial criteria.

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