Connect to Online Data

This function can also be accessed in the File toolbar.

The Connect to Online Data command allows the user to download mapping data from numerous built-in and user-supplied sources. This includes premium access to high resolution color imagery for the entire world from DigitalGlobe, worldwide street maps from OpenStreetMap.org, as well as seamless USGS topographic maps and satellite imagery for the entire United States.

In addition, access is provided to several built-in WMS (OpenGC Web Map Server) databases to provide easy access to digital terrain data (NED and SRTM) as well as color satellite imagery (Landsat7) for the entire world. New WMS data sources can be added for access to any data published on a WMS server.

Note that this feature requires Internet access to work.

Select an Online Datasource from the list of built in sources.

If data is already loaded, the Select Area to Download will default to the current screen bounds.

If no data is loaded, use the within an address or within a latitude, longitude options to specify a location to request data for.

With slower internet connection, optionally choose to Restrict Source to Selected Bounds to just perform a one-time download of the relevant data. If the selected data is loading with labels that are too small to read, or an otherwise inaccurate zoom level for the map display, modify the Detail Level requested using the slider.

Press the Connect button to download the data.

Most online sources will download directly into the map. Some sources, such as satellite image archives, require additional selection within a web browser, but the requested data extent will automatically be included in the data request in the browser.

Select Area to Download

The Select Area to Download setting defines the initial extent of the data to be downloaded. Choose from the following options:

Current Screen Bounds - This setting will download the data to cover the extent of the current screen bounds

Within distance of Address - This setting will use address geocoding to request and download data contained within the square extent of the distance radius. It will also place a label at the indicated address.

Within distance of Latitude, Longitude - This setting will download data contained within square the extent of the distance away from the specified Latitude, Longitude value.

Specify Latitude/Longitude Bounds of Area - This setting allows specifying a custom bounding box for downloading data. Use the Draw a Box button to dynamically draw an extent on the existing map.

Download within Currently Selected Polygon(s)- Downloads data contained within the bounds of the currently selected polygon, and clips the data to the polygon(s).

Entire Data Source Bounds - Downloads the entire bounds of the datasource.

Check the Restrict Source to Selected Bounds option to restrict the selected data source to availability within the user-specified bounds. It is then possible to pan around the entire data source, but the default view will be the bounds specified.

Data Resolution

Once the data to download is defined, Global Mapper will automatically download the most appropriate zoom level to display as the map is zoomed in and out. An overview of the data will be visible when zoomed out, with more detail becoming available when zoomed in. This allows directly loading the image files from the cache in the temp folder as well as adding them to a map catalog, allowing easy offline access to downloaded online tiles. (To include World or PRJ files for the data in data downloads, go to the General Advanced section of the Configuration dialog and under Miscellaneous Options, select Save World/PRJ Files for Download Tiles. Once selected, world files will be automatically generated for all tile images downloaded from an online source, in addition to a default.prj file. Both the world and prj files are saved to the image download folder.)

The data can be exported in full resolution to any of the supported raster export formats, such as GeoTIFF, JPG, or ECW. The most appropriate detail level for the export sample spacing will be used to obtain the source data for the export.  

Each data source load will then appear as a separate layer in the Overlay Control Center. Each entry can have its display options modified just like any other raster layer to drape it over elevation data, blend it with other layers, etc.

Under Display Options, Resampling Method has a drop down menu that allows for the selection of a specific Resampling Method. This can add clarity to streaming data, depending on whether or not resampling is enabled. The default setting is bicubic. The Detail Level will allow online layers to draw data at a lower resolution than the screen for faster display, allows for control of online layers so that you can pull from lower or higher resolution layers, rather than the default screen resolution calculation.

Data Source Context Menu

Right-click on a datasource to see the following options:

Edit Source Name/Group - This option will allow you to edit the Source Name for the online data source, or the Group the source belongs to. This option is not usable on built-in data sources.

Save Selected Source Definition(s) to XML File... this option will save the online source definitions for user defined online data services to an XML file. This option is not usable on built-in data sources.

Set the Maximum Resolution to Obtain Data from this Source - Use this option define a maximum resolution for data downloaded from the selected source.

Draw Using Tiles - Select this option for selected download areas to be drawn using tiles.

To specify whether or not to download as tiles when drawing or to download a single image for each draw operation, right-click on the added WMS layer in the list of sources. The default is to use tiles as that allows caching, so that if an area is revisited at the same zoom level re download is not needed. However, if a specific source adds a watermark to each tile this may be undesirable.

Uncheck this option to disable the use of tiles for display. The tiles will still be used for export, as the size of exports makes it impossible to fetch all at once in many cases.

Display Source Webpage/ Terms of Service- Provides additional information and metadata from built in sources. The source information for built in sources can also be seen once a source is loading by opening the Metadata and viewing the Additional tab.

Adding Custom Online Sources

Use the Add New Source button to add new online sources of imagery from WMS (Web Map Service), WCS (Web Coverage Service), OSM (OpenStreetMap Tiles), Google Maps-organized tiles or TMS (Tile Map Service) sources. When selected, a dialog appears allowing the user to choose the type of source to add.

If the source highlighted in the list matches the source type specified in the Select Online Source Type dialog, the values from that source will automatically populate in the Tile Source Definition or Select Data Source dialog.

Once a source is added, it can be removed with the Remove Source button at a later time. When you add or edit an added source and specify the Category or categories, nested categories /groups can be created in the source list by adding ' --> ' in the Category name.

Example:to name the category 'U.S. DATA --> Maine' to create a nested source group:

-U.S. DATA
-Maine
-Source Name

Troubleshooting

When no tile data is visible once connected to the source, use the option in the Control Center right click context menu to Draw Online Layer Missing Tile Boundaries to display outline and labels of the tiles.

Managing Sources

Delete Cached Files...

Use the Delete Cached Files button to remove any locally cached files from any particular type of data sources. This is useful if the online data may have changed or if you have downloaded corrupt files somehow. See also Temporary Files folder in Advanced Configuration for location of cached files.

Add Sources From File...

Use the Add Sources From File button to add new WMS sources from an external text file. Web tile formats exported from Global Mapper will create a *.gm_source_def.xml file that can be added here to reload the exported tiles. This XML file is also created by right-clicking on an existing custom source and selecting Save Selected Source Definitions to XML file.

This provides an easy way to share your list of WMS sources with other users, by providing them with the user_online_sources.xml from the User Data and they can load that file with this button to add their sources to your source list.