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, 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.

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.

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.

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.

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:

-Source Name


If the WMS or WCS options are selected, then the Select WMS Data Source to Load dialog (pictured below) is displayed. This dialog allows the user to specify the URL of a WMS or WCS data source and select what layer(s) to add as an available data source on the Select Online Data Source to Download dialog.

The URL that is used should by the GetCapabilities URL (such as for the JPL WMS data server). Once the URL has been entered, press the Get List of Available Data Layers button to query the server and populate the data control with the available data layers on that server.

For WMS v1.1 support, select the option to 'Prefer WMS 1.1.1 Over Newer Versions'.If not selected the default is v1.3.


To force the use of the JPG format, you might specify a Service Name parameter of 'WMS&format=image/jpeg'. To force a particular projection that the server supports to be used, include a SRS parameter, like 'WMS&SRS=EPSG:26905' to force the use of the UTM projection with the NAD83 datum and zone 5N.)

To specify additional options for the WMS server, such as forcing a particular image format to be used, add those parameters after the Service Name parameter.

Select the data layer and style and press OK to have it added to the available data source list.

Maximum Zoom

To set a maximum zoom level, right-click on the added WMS layer in the list of sources and set a maximum zoom level (in meters per pixel) for the layer.


You can specify a maximum zoom level of 5.0 meters per pixel, so when loading data from the source no tiles with a resolution greater than 5.0 meters per pixel will be downloaded. This is useful for sources that don't specify themselves what the maximum resolution should be and just go blank when you over zoom them.

OSM/ Google Maps / TMS

If OSM, Google Maps, or TMS source type is chosen, then the OSM/TMS Tile Source Definition dialog (pictured below) is displayed, allowing setup the source to be defined. The base URL will need to be specified, where the data for the tiled source can be found (this should be the folder under which the folders for each zoom level are stored).

A URL with variables named %x (column), %y (row), and %z (zoom scale) in the URL can also be used, so that the URL can be setup however the data source requires, rather than using the default expected URL setup.

If accessing a source setup similar to Bing Maps tiles, it might be necessary to use the quadtree filename. Use %quad to do this. This replaces the %x, %y, and %z values. Finally the Bing Maps RESTful services supports accessing via the zoom scale (%z) and a latitude and longitude value in the tile. Use %lat and %lon to include the latitude and longitude of the center point of the tile in your custom URL.

Image File Type

It will be necessary to specify if the source uses PNG or JPG image files .

Max Zoom Level

Provide the maximum zoom level to use when loading the source.

Tile Size

Specify the size of the tiles in pixels. This will be included in <TileSize> in the xml file.

Native Projection

Specify the projection used for the tiles.

Lat/Long Bounding Box

Specify the bounds of the data source in degrees latitude longitude.


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

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.

Use the Add Sources From File button to add new WMS sources from an external text file. This provides an easy way to share your list of WMS sources with other users, by providing them with the wms_user_sources.txt file from the Application Data folder (see the Help-> About dialog for the location of this folder) and they can load that file with this button to add their sources to your source list.

The Load ECW from Web button allows the user to open an ER Mapper Compressed Wavelet (ECW) image file directly from an Image Web Server URL using the ECWP protocol. While these files may be terabytes in actual size, only the portion needed for the current display window is downloaded, allowing for the browsing of extremely large data sets.

Selecting the Load ECW from Web displays the Load Image From Web dialog (pictured below). This dialog allows the user to either select a predefined web link for loading or to enter the URL of any available ECW file served by Image Web Server.  


The tree on the left of the dialog allows the user to select which data file they wish to load. Global Mapper comes with several dozen useful links already entered into the tree.

To access a specific ECW image from the web, press the Add Link... button. This button causes the Add New Web Link dialog (pictured below) to be displayed.

The Group Name drop list allows the user to select which group, if any, to place the new link in. Any of the predefined groups can be selected, or a new group name can be entered. Leaving the group name blank will cause the new link to appear at the root level of the tree.

The Description field is where the name of the link is entered. This is what will be displayed for the link on the main dialog. Leaving this blank will cause the URL to be displayed instead.

The URL field is the most important piece of this dialog. This is where the address of the ECW file to load is specified. The URL should begin with the prefix ecwp:// with the remainder being a valid path to an ECW file served using ER Mapper's Image Web Server software.

Once entering the information about the new web link is completed, press the OK button to complete the entry and have it added to the web link tree in the Load Image From Web dialog.

Pressing the Edit Link... button allows the user to edit the currently selected web link. Note that the built-in web links cannot be edited.

Pressing the Delete Link... button will delete the currently selected web link or group from the web link tree.

An error message indicating that the settings have been updated to support the ECWP protocol whenever an attempt is made to load an ECW layer from the web indicates that it is necessary to download and install the latest ECW ActiveX plugin