Transpose locations from an image to a map

First, you will use an image from a news report and transpose the locations of damage onto a map of the Main Street area.

Familiarize yourselves with the affected area

In this section, you will download the image showing damage along Main Street and familiarize yourself with the area affected.

  1. Download a full-size version of the image.

    In the image, damaged and destroyed buildings are identified by a red marker. Notice Main Street and nearby roads are labeled, which will help us identify this location on a map. Also notice the orientation of Main Street, an east-west road, is rotated in the image.

    Damaged buildings

    Leave this image open in your browser as a reference. You will recreate this photo in your map.

  2. Sign in to your ArcGIS organizational account.
    Note:

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

  3. On the ribbon, click the Map tab.

    Click the Map tab.

    Note:
    Depending on your organizational and user settings, you may have opened Map Viewer. ArcGIS Online offers two map viewers for viewing, using, and creating maps. For more information on the map viewers available, please see this FAQ.

    This lesson uses Map Viewer Classic.

  4. If necessary, on the ribbon, click Open in Map Viewer Classic.

    Open in Map Viewer Classic

    Map Viewer Classic opens.

  5. On the ribbon, in the Find address or place search bar, type Main St and McFerrin Ave, Nashville.

    Find address or place search bar

  6. Zoom in and out and identify buildings on your map with the buildings in the image.

    Compare the geometry of buildings and streets to understand how the photo would overlay onto your map. Familiarize yourself with where the damaged buildings are on your screen.

    Tip:

    Use the unique angle at the intersection at McFerrin Ave and Main Street to find your reference points.

Next, referencing the image, you will mark each damaged or destroyed building on the map using a map note.

Adding map notes

A map note is not traditional GIS point data with an attribute table, but it is a quick way to mark locations and add a small number of features to a map.

  1. On the ribbon, click Basemap. Choose the Imagery basemap.

    Select the Imagery basemap.

  2. On the ribbon, click Add. Choose Add Map Notes.

    Add Map Notes

    The Add Map Notes window appears.

  3. For Name, type Reported Damage.
  4. On the Template drop-down menu, choose Damage. Click Create.

    This provides symbols you will use to mark the damaged and destroyed buildings.

    Add Map Notes window

  5. On the Add Features menu, choose the Affected symbol.

    Choose the Affected symbol for Add Features.

  6. Place it on a building that matches the damaged building in the image.

    Place a map note on a damaged building.

    Note:

    While there are other features that may seem appropriate, such as Destroyed or Building Affected, you are not distinguishing between damaged and destroyed buildings at this point. You just want to label the structures from the news photo as Affected on your map.

  7. In the Damage pop-up window, click Change Symbol.
  8. On the Shapes tab, scroll until you see the red dot symbol. Select the red dot. Click OK.

    Select the red dot symbol

  9. On the Damage window, click Close.

    You will now see a red dot on top of the affected structure.

    Note:

    To get back to the Add Features window, click Edit on the toolbar.

  10. Continue adding Affected map notes until you have included all the structures from the news photo.

    Map of all damage location points

  11. On the ribbon, click the Edit button to close the editing session.
  12. On the ribbon, click Save and choose Save As.

    Save As

    The Save Map window appears.

  13. In the Save Map window, enter the following information:
    • For Title, type Tornado Damage.
    • For Tags, type Tornado.
    • For Summary, type EP3 Tornado March 2020 Nashville.

    Save Map window

    Next, you will publish the map note layer to your ArcGIS Online account.

  14. In the Contents pane, for the Reported Damage layer, click More Options. Choose Save Layer.

    Choose Save Layer.

    The Create Item window appears.

  15. In the Create Item window, enter the following information:
    • For Title, type Reported Damage Saved.
    • For Tags, type Tornado.
    • For Summary, type Damaged or Destroyed location area layer.

    Create Item window

  16. Click Create Item.

Next, you will generate a grid to assist the damage assessment team in demarcating which areas are damaged and destroyed due to the tornado.


Generate a grid tessellation and identify cells (bins) with damage

One way to efficiently plan for ground assessments is to divide an area of interest into a grid. Overlapping this grid with the damaged buildings layer will allow you to send crews to areas with reported damage first. These grids are referred to as tessellations, and the grid cells are called bins.

In the first section, you created a layer capturing all the damage reports and symbolized each point. Now, you'll assist the damage assessment team by dividing the area into sectors using the Generate Tessellations analysis tool.

Generate Tessellations tool

The Generate Tessellations tool creates tessellations, or bins, determined by a specified extent, shape, and size. In this section, you will define the area of damage to generate the bins using this tool.

  1. On the ribbon, click Analysis.

    Analysis tab

  2. In the Perform Analysis pane, click Manage Data, and on the drop-down menu, choose Generate Tessellations.

    Choose Generate Tessellations.

  3. For Choose shape, select Square from the drop-down menu.

    Choose Square shape from the drop-down menu

  4. For Define extent, click the Draw tool.

    When you hover over your map, a pop-up window says Click to start drawing.

    Click the Draw tool.

  5. Create a polygon around the damaged buildings. Double-click to finish the drawing. Check the box next to Only keep intersecting tessellations.
    Note:

    Once you start drawing, the pop-up window changes from Click to start drawing to Double click to finish drawing.

    Notice that the Drawn Polygon Layer option is automatically chosen once you draw the polygon.

    Drawn Polygon Layer is chosen automatically

  6. For Define bin size by specifying, select the Distance option. Type 250 and select Feet from the drop-down menu.

    Define bin size settings

  7. For Result layer name, type Nashville Damage Assessment Tessellation followed by your name. Uncheck Use current map extent.

    Type the result layer name.

    What do these parameters mean?

    Choose shape— Each cell in the tessellation is called a bin. You are choosing the shape of the bin. Shape options include square, hexagon, transverse hexagon, triangle, and diamond.

    Define extent—The extent of your tessellation can be defined by a boundary you draw, an existing boundary layer, or the current extent of your screen.

    Only keep intersecting tessellations—All bins can be kept (in a rectangular tessellation covering your boundary area), or only the bins intersecting your extent can be kept.

    Define bin size by specifying—The size of each individual bin can be entered according to the desired area of the bin or the distance (width) of the bin.

    Note:

    Checking your credit consumption is critical with this tool because credit usage goes up with more bins. If you accidentally size your bins too small, more bins will be created to fill the tessellation and the credit cost can be high. As a guide, about 1 credit or less should be required for this tessellation. Check your credit consumption by clicking the Show Credits link.

  8. Click Run Analysis.

    A tessellation covers your damage area, and only those bins intersecting your drawn boundary are included.

    Resultant layer with blue outline

    Note:

    Your drawn boundary may differ.

In the next section, you will change this outline of this layer.

Change Style of the layer

The blue outline for the tessellations is tough to see with the Imagery basemap. You will change the outline of the Nashville Damage Assessment Tessellation layer to a color that is easily seen. Since the basemap is darker color, a lighter color is the best choice.

  1. In the Contents pane, for the Nashville Damage Assessment Tessellation layer, click the Change Style button.

    Change Style button

  2. In the Change Style pane, click Symbols.

    Click Symbols.

  3. In the Symbols window, for Fill, select No color.

    Select No color for Fill.

  4. Click Outline, and choose a color that is easily seen, like white.

    Choose white color outline.

  5. Click OK. In the Change Style pane, click OK again and click Done.

    Map with the change in symbology

  6. Provide a unique name for your resulting layer.

Symbolize bins to prioritize response

In the same way that damage assessors inspect their sector of a grid and mark it complete, you will symbolize each bin in the tessellation to represent whether it contains reported damage or not.

Add a field and enable editing

Feature layer edits include adding, altering, or deleting the features on the map, as well as adding, altering, or deleting the information (attribute values) associated with the features. In this section, you will add a field and enable editing on the Nashville Damage Assessment Tessellation layer.

  1. In the Contents pane, for the Nashville Damage Assessment Tessellation layer, click the Show Table button.
    Click the Show Table button
  2. In the attribute table, click Options and choose Add Field from the drop-down menu.

    Choose Add Field from the drop-down menu.

    The Add Field window appears.

  3. In the Add Field window, for Field Name type DamageYesNo.
  4. For Display Name, type Contains Damaged Buildings. Click Add New Field.

    Add Field window

    Note:

    Field Name is used in the background by the ArcGIS software and must be one word without spaces, while Display Name is what will show to you as the header of this field in the table.

    In the Contains Damaged Buildings field, you will manually enter if the building is damaged or not. But first you must make the layer editable.

  5. In the Contents pane, for the Nashville Damage Assessment Tessellation layer, click the More Options button and select Show Item Details.

    Show Item Details

    The Item Details page of the layer opens in another tab on the web browser.

  6. On the blue ribbon, click the Settings tab.
    Click the Settings tab.
  7. Scroll to the Feature layer (hosted) section. Under Editing, check the Enable editing box.
    Check the Enable editing box.
  8. For What kind of editing is allowed, under Update, choose the Attributes only option.

    This will prevent bins from being accidentally moved while editing the attributes.

    Check the Attributes only option under Update
  9. Click Save to save these settings.
  10. Browse back to the Tornado Damage web map. Save the web map and refresh the web page.
  11. On the ribbon, click the Edit tab.
    Edit tab

In the next section, you will classify the bins as damaged or not.

Classify bins

Symbols graphically describe, categorize, or rank geographic features and labels to locate them and show qualitative and quantitative relationships. They display graphical elements on a layout.

In this section, you will select each bin and classify it as damaged if there are any reported damaged buildings present. You will use symbology to differentiate between the damaged and not damaged areas.

  1. Click a bin. In the pop-up window for Contains Damaged Buildings, type Yes or No depending on if it contains any Reported Damaged layer points.
    Type Yes or No depending on the Reported Damaged layer.
  2. After one example of each, close the edit session by clicking Edit again.
  3. In the Contents pane, for Nashville Damage Assessment Tessellation layer, click the Change Style button.
  4. In the Change Style pane, on the Choose an attribute to show drop-down menu, select Contains Damaged Buildings.
    Choose an attribute to show drop-down menu with Contains Damaged Buildings selected
  5. For Select a drawing style, on Types (Unique Symbols), click Options.
    Click Options
  6. For Yes, click to change a symbol and select any shade of red. Similarly, for No, select any shade of green. Click OK.

    Contains Damaged Buildings symbol colors

    You can increase the transparency of the layer to see the underlying buildings and streets. 50% transparency works well.

  7. In the Change Style pane, click Done.
    The bins symbolized as Yes and No
  8. Return to editing and classify each bin as damaged or not by clicking the bin and typing Yes or No.

    Now each bin automatically changes color as you enter each attribute.

    Final symbolized map

    Note:

    The final map with the bins will vary depending on the polygon drawn in the previous section.

You now have a map of the reported areas of damage from the tornado, and assessor teams now have an idea of where to prioritize their mission.

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