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  4. External Map Layers Command

External Map Layers Command

Maps are composed of a series of map layers drawn in a particular order. A map layer defines how a GIS dataset is symbolized and labeled in the Map View. Examples of map layers include streams and lakes, terrain, roads, subbasins, building footprints, orthophoto imagery, and more.

In CivilGEO’s software, the user can use the External Map Layers command to add an additional map layer on the Map View using external map services.

Follow the steps below to use the External Map Layers command:

  1. From the Map Data ribbon menu, select the External Map Layers command.
    External Map Layers-Map Data ribbon menu command
  2. The External Map Layers dialog box will be displayed.
    External Map Layers dialog box

The following sections describe how to use the External Map Layers command and interact with the above dialog box.

Adding an External Map Layer

The Map Layer Catalog panel allows the user to add external map layers on the Map View, import the map layer from the catalog file (collection of map files), or export the map layer into the catalog file.

To add additional map layers on the Map View, follow the steps below:

  1. From the Select Map Layers to Load section, select the desired map layers by checking the checkboxes corresponding to the map layer to be loaded on the Map View. Two available map layers catalogs are:
    • FEMA Flood Data: This option contains all the layers from the FEMA map service.
    • National Levee Database: The option contains information about the location and condition of levees and floodwalls, displayed in an easy-to-use map interface.
      Note that the user can expand these options to see the available map layers.
  2. The user can see the details of the selected map layer (Name, Version, and Abstract) in the Map layer details section.
  3. After selecting the map layer(s), click the [Load Catalog] button.
  4. The software will then add the selected map layers as a new group in the Map Data Layers panel and display it on the Map View, as shown below.
    Map Data Layers panel - Map View

Importing a Map Layer

The user can click the [Import Catalog] button to import the map layers on the Map View.
[Import Catalog] button

On clicking the [Import Catalog] button, the software will display the Import Catalog dialog box. The user can select the catalog file (it should have a file extension of .cat) and click the [Open] button.
Import Catalog dialog box

This will add the selected map layer catalog in the Select Map Layers to Load section of the Map Layer Catalog panel. The user can then select the sublayers of this newly added catalog and add them to the Map View.

Exporting a Map Layer

The user can click the [Export Catalog] button to export a map layer in a catalog file.
[Export Catalog] button

On clicking the [Export Catalog] button, the software will display the Export Catalog dialog box. The user can browse to the desired location to save the file, enter the file name, and then click the [Save] button to save map layers as a catalog file.
Export Catalog dialog box

Creating a New Map Layer

The Create New Map Layer tabbed panel allows the user to create a new map layer using the WMS (Web Map Service) services. A Web Map Service is the standard protocol for transferring map layers over the Internet.
Create New Map Layer panel

To create a new map layer, follow the steps below:

  1. In the Map Server Connection section, enter the map server URL in the Map server URL input field to load the map layer. By default, the software uses the NLD WMS service URL.
  2. From the Data source type dropdown combo box, select the data source type. By default, the software uses the WMS (Web Map Service) data source type.
    Note that the software currently supports WMS (Web Map Service) data source type only.
  3. From the Version dropdown combo box, select the appropriate version of the map service. By default, Auto is selected.
    Map Server Connection section - Version dropdownSometimes the service requires authentication for establishing the connection. Follow the steps below to authenticate a connection:

    1. Select the Authentication panel under the Map Server Connection section.
      Authentication panel
    2. Enter the username in the User name input field.
    3. Enter the password in the Password input field.
    4. Alternatively, check the Save password checkbox option. Checking the Save password checkbox option does not require relogging every time you go to that URL..
    5. The software will automatically attempt the authentication when trying to download the sublayers.
  4. Click the [Get Sublayers] button. When the connection to the map service is successful, the software will download all the available sublayers corresponding to the specified URL and list them in the Select Sublayers to Use section.
    [Get Sublayers] button
  5. From the Select Sublayers to Use section, check the checkboxes corresponding to the sublayers to include them in the map layer catalog.
  6. From the Image format dropdown combo box, select the image format that will be used to represent the map layers on the Map View. By default, Auto is selected.
    Image format dropdown
  7. From the Projection dropdown combo box, select the projection to assign the CRS (coordinate reference system) for the loaded map layers. By default, WGS 84 (deg) is selected.
  8. In the Add Defined Map Layer to Catalog section, enter the source name into the Source name input field. This name identifies the map layer group that will be created in the Map Layer Catalog panel that will contain the selected sublayers.
  9. Click the [Store Map Layer] button. Note that this button is enabled only when at least one sublayer is selected in the Select sublayers to Use section, and the source name is defined in the Source name input field.
  10. The newly created map layer information will be created in the Map Layer Catalog panel, as shown below.
    Map Layer Catalog panel

About the Author Chris Maeder

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