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Preparing Data for Input into Geospatial Applications: Case Study

This is a guide to help Virginia Tech community members prepare their data before inputting it into a geospatial software/application.

The spreadsheet we will be using is Mosquitos_in_Gambia. This spreadsheet has the following issues:

 

Issues Identified
Recommended Improvements

Coordinate Formatting:

  • The Latitude (LAT N (° min sec)) and Longitude (LONG W (° min sec)) columns are a mix of decimal degrees and degrees-minutes-seconds (DMS). ArcGIS Online generally requires coordinates in decimal degrees for accurate mapping.

Convert DMS to Decimal Degrees:

  • Convert the Latitude_DMS and Longitude_DMS values to decimal degrees.

Column Naming:

  • The column names contain special characters like (° min sec), which should be avoided.
  • Use clear, concise, and consistent headers like Latitude, Longitude, Altitude, Collection_Site, and Trap_Type.

Clean and Standardize Column Headers:

Rename columns as follows:

  • Collection → Collection_Site
  • LAT N (° min sec) → Latitude_DMS
  • LONG W (° min sec) → Longitude_DMS
  • Altitud → Altitude_m
  • Site → Site_Name

Empty Columns:

  • The Unnamed: 7 column contains mostly empty values and should be removed.

Remove Empty Columns:

  • Drop the Unnamed: 7 column.

Mixed Data Types:

  • The Altitude column contains values like "10m", which should be converted to a numerical format (e.g., 10 without the "m").

Format Altitude Properly:

  • Remove the "m" suffix from the Altitude values and ensure they are numeric.

Consistent Site Names:

  • Collection and Site columns have inconsistent spacing (e.g., AGRI2 vs AGRI 2), which can lead to grouping issues in GIS.

Check for Duplicates and Consistency:

  • Make sure site names and collection labels are consistent across the entire dataset.


While these issues can be considered common ones to be addressed, the primary geospatial data you collect will not necessarily have the exact same issues.

  1. Create an ArcGIS Online by following the instructions on this LibGuide: Creating an ArcGIS Online Account
  2. On the same virginiatech.maps.arcgis.com page where you created your ArcGIS Online account, click “Map” on the menu bar. 

  1. When you click on ‘Map’, you will see a page with a default reference map of raster data called a ‘basemap’. This basemap will be focused on the contiguous United States. You can leave this basemap as it is, but if you want to change it, you will:
  • Click on the Basemap, and the Basemap pane appears
  • Click on any thumbnail of the basemap that you want to use in the map (scroll down for more options)What you see depends on the scale you are working on on your map - as you zoom in closer, you will typically find more detailed information. Your scale is displayed below the map and automatically adjusts as you zoom in and out.You can use the scroll button on your mouse to zoom in and out of the map, and you can left-click and hold to pan around the map.

 

The data we are working with is secondary data to you since you did not collect it directly from the field.

  1. Click the dropdown on the “Home” button on the top left and select “Content”.

  1. Select “New Item”and navigate to your working folder where you downloaded the data by selecting “Your device”and the zipped file of the first layer.
  2. Under ‘How would you like to add this file?’ select “Add ‘filename’ and create a hosted feature layer” and click “Next”.
  3. Check the boxes for all columns you want to import from your CSV to ArcGIS Online.
  4. The title of your file will be the file name (feel free to change it), under ‘Folder’ select “Create new folder” and add the folder name. 
  5. Add tags and a summary to the layer if you want, then click “Save”. A layer will be added.
  6. Select “Open in Map Viewer Classic”and the layer will be added to your map.
  7. When prompted to change style, select the " Single Symbol" option and click “Done”.
  • You should have your layer on the map, which can be seen in the Contents pane on the left. 
  • You can right-click on any layer and select Zoom to Layer to center it on the screen.

  1. Zoom in and out of your map using the scroll button on your mouse, using two fingers on your touchpad, or right-clicking and holding down.
  2. You can turn the layer on and off by checking/unchecking the box next to each name, making it easy to see the other data layers.

 

Exploring the Attribute Table

  • Every point, line, or polygon file has an attribute table. 
  • Click on the table icon under each layer to look at its data.
  • Any data in the attribute table can be used for displaying and labeling on the map and making queries. 
  • You can also create new columns in the table and add data or calculations.
  • Metadata can be key to understanding attribute tables that use codes and abbreviations.

Data can be symbolized in a variety of ways, depending on the data format and available attributes. You can choose different symbols to represent the features you've added to the map. For example, water bodies and streams might be shown with a single, constant blue color, while roads might be symbolized based on road class. Additionally, you can use smart mapping styles such as dot density to find more meaning in the data. 

Changing a Single Symbol

  1. In the Layers/Contents pane, click the ‘Mosquitos_in_Gambia’ layer to select it.
  2. On the Settings toolbar, click the icon for ‘Styles’ and go to “Options” under ‘Location (Single symbol)’
  3. Under “Choose an attribute to show”, select ‘Collection’.
  4. Select “Options” under ‘Location (Single symbols)’ , click ‘OK’ and ‘Done’.

 

Symbolize Categories

  1. In the Layers/Contents pane, click the ‘Places of Interest’ layer to select it.
  2. On the Settings toolbar, click the icon for ‘Styles’ .
  3. In the ‘Styles’ pane, under the ‘Choose an attribute to show’ dropdown menu, select “Collection”.
  4. Select the option that says ‘Types (Unique symbols)’.
  5. The points in your map will be categorized based on the data that is in the ‘TYPE’ column of the attribute table (colors may differ from the image below).

  1. Select “OPTIONS”. A new pane will open with the labels and their count number.
  1. Click on the first dot icon of ‘AGRI1’ to change the symbol.
    1. This layer has 31 unique features; therefore, after categorizing it as ‘Unique symbols’, you will notice that only 10 features will be categorized, and the other 14 will be grayed out and fall under ‘Other’.
    2. To fix this, click the “Ungroup” icon and all 31 fields will be displayed uniquely.
  2. Select “Shape” and in the dropdown menu select the shape that you want to use to symbolize your data.
  3. Change the symbol size in pixels using the scale bar under this pane, and click “OK”.
  4. Do this for all symbol categories and select “OK”, then click “DONE”

 

Labeling your Map

Now we will add labels on the map so we can easily identify the neighborhood names.

  1. Click on the ‘Mosquitos_in_Gambia’ layer so that it is selected, and click on the 3 horizontal dots.
  2. Select ‘Create Labels’ and the Collection names will be added to the map.
  3. You can change the different ways that your labels appear, are positions, placed, etc. in the pane that opens, then select “OK”.
  4. Save your map project.

 

Define the map legend

When you start a new map or open a saved map of your own, it opens with the Contents pane showing. When anyone else opens your map, however, it opens with the Legend pane showing. You should think about how you want the legend to look. On the left toolbar, click the ‘Legend’ button. 

Note: Legend entries are created for all layers except the basemap.

  1. Click on the “Save” icon on the menu bar and select “Save As”. A tab will open where you need to fill in information.

  1. Type a title. A title is required to save the map.
  2. Type the tags that describe the map.
    • Tags are words or short phrases that describe a map. Separate the terms with commas. Virginia Tech Blacksburg is considered one tag, while Virginia Tech, Blacksburg is considered two tags.
  3. Type a summary that describes the map.
  4. Choose a folder in “My Content” where you want to save the map.
    • If your organization (Virginia Tech) has set up content categories, use the drop-down menu to select one or more categories for the map.
  5. Click on the “Save” icon on the menu bar and select “Save” and keep your project open.

 

Sharing your ArcGIS Online Map

When creating or modifying a map that you own, sharing is possible, provided you have the necessary privileges for content sharing. Additionally, administrators within an organization can share a web map directly while it is being viewed in Map Viewer. Follow the following steps to share the map while you have it open:

  1. Click on the ‘Share’ icon from the Menu bar.
  2. When you first create the map, it is automatically set to private. If you want to change this and share the map with others, check the box(es) on the pane.
  3. If you are a member of any group within ESRI, you will also be prompted to share the map with these groups (not required).

  1. You can also copy the link to the map, which can be shared with anyone (checked in the boxes above) to view.
  2. Once you finalize this, select ‘Done’.