Datasets on GeoBase are offered in multiple file formats. Each format has benefits and its own methods of use. Provided below are descriptions and some examples of software that facilitate the use of each.

ESRI shapefile

The shapefile (.shp) is a popular data format developed by the company ESRI and largely used with their ArcMap and ArcView software packages. It has continually grown and now serves as one industry standard; many other GIS platforms, both free and proprietary, have adapted to allow interoperability with this file format. In a shapefile, each record represents a basic geographic shape – line, point, or polygon – that can be displayed or modified in the appropriate software to produce geographic analysis.

Digital Elevation Model (DEM)

Digital Elevation Models (DEMs) are a digital representation of earth’s surface height over a set or grid of geographic coordinates. They are the most common base for ‘three-dimensional’ relief maps of the earth’s terrain. All major GIS software packages have a toolset for processing DEMs. Some smaller applications specializing in extrapolation of the earth’s surface, such as MicroDEM, are also available for free download.

For further links and recommendations to software used to view downloaded data, refer to the FAQ through the link at the bottom of any GeoBase page, and click on the question, "How can I open a vector data file if I don't have GIS Software?".

Geography Markup Language (GML)

GML is a text-based representation of geographic information, and it is a specific language for representing geodata with simplicity and usability via the Internet. It is a way of including encoded geographic properties in a way that can be understood by any Internet server or browser. When a GML document is included in an internet tool, the features it describes are interpreted into a map or graphical representation in the style specified by the web page designer or user. Commands built into a web page can reference specific elements within this document and change the way they are displayed by a web browser or other software.

Some free GML Viewers can be found for download. These allow for simple viewing of the geometric shapes described in the file, as well as the attributes and values assigned to each.

Keyhole Markup Language (KML)

KML files also use text-based encoding of geographic information and are intended to express geographic features for the purpose of two- or three-dimensional visualization. Their use of features and information is limited to internet-based Earth browsers and the Google Earth application.  

Similar in format, KMZ – a compressed-folder version of the KML – is made available for the National Hydro Network datasets. They are split into smaller files and compressed in this way to allow the Google Earth application to handle the information, but in some cases the resultant file may still be cumbersome and result in slower performance.

To view KML/KMZ files in this application:

1. Download and Install from the Google Earth website.

2. After successful installation, run the application and choose File > Open from the menu bar.

3. Navigate to the location of the files downloaded and saved from GeoBase. Click Open (Figure 20).


Figure 20:  Open files in Google Earth

4. In larger data sets like the National Hydro Network KMZ in this example, the file first appears in Google Earth as a shaded region (Figure 21).


Figure 21: First appearance of NHN file

5. Zoom In on the shaded area using either the zoom control in the upper right corner of the Google Earth interface or the mouse’s scroll wheel. By zooming to a small enough area, lines representing hydrographic features will appear. At an even closer view, points containing information for each feature will appear.

6. Click on points appearing on the Earth’s surface to view an information window describing the feature found in the downloaded file (Figure 22).

Figure 22: NHN Google Earth Info Window

7. The window displayed by each point shows the GeoBase dataset in which the point can be found (top-left of info window) and selected attributes that describe the type of information the point represents.

8. Refer to the data layer Description and Documentation page for feature catalogues and attribute profiles. Here, attribute definitions and data layer information can be found in greater detail.