Digital data can be imported from other sources. Often data are obtained already in digital format from Government Agencies such as Australian Geological Survey Organisation http://www.agso.gov.au , the Australian Survey and Land Information Group (AUSLIG) http://www.auslig.gov.au , and other sources. This is becoming a very common way to populate databases.

Some data is being made available on the internet by many organizations and agencies. The US Federal Geographic Data Committee's web page at http://www.fgdc.gov has the US National Geospatial Data Clearinghouse containing links to hundreds of organisations that maintain and provide GIS data, both in the US and around the world. In some cases, you can download the data directly and use it in GIS packes such as ArcView. ESRI's web page (http://www.esri.com) also contains links to organizations that maintain and provide GIS data. From the web page you can access the Data Hound, a good place to a search for data. The Data Hound offers links to other GIS sites that offer free, downloadable data.

The issue then becomes one of transferring the data from the supplied format into that needed.

When GIS first began to appear, users either developed their own formats for storing spatial information or employed those defined by data holders and their software. The formats were often specific to the needs of particular projects and were not intended to meet the needs of a broader range of users. It was often very difficult to share and transfer data. Users recognized that much time and money was being wasted when datasets could not be shared among a broader clientele. The United States Geological Survey (USGS) was one of the first agencies to begin experimenting with data formats that could serve both their needs and those of a wider public. The USGS's digital line graphs (DLG) was the result, although both of these early formats have since been further refined into the DLG-2 format. The DLGs were a way of coding information drawn from the USGS's conventional paper quadrangle sheet maps.

The development of standards and the proliferation of conversion and translation software has had a large effect on the GIS world. Where once users had to count on digitizing datasets from scratch, they can now use a wide range of publicly available files. The growth in available files has been huge. The emergence of new data transfer standards may increase the pace of development further.

Common data transfer formats include:

Australian Spatial Data Transfer Standard (SDTS)
DXF (Drawing Exchange File)
J PEG files
VPF (Vector Product Format data Most GIS packages now contain a suite of software algorithms that will perform the necessary data transfers.

The data obtained from other sources should contain meta-data, that is data about the data, or a sort of "data quality report" from the provider. This will provide a description of exactly what is in the file, how the information was compiled (and from what sources), and how the data was checked. The documentation for some products is quite extensive and much of the detailed information may be published separately.

If documentation is limited, it is important for you to consider the following questions:
What is the age of the data?
Where did the data come from?
In what medium was it originally produced?
What is the areal coverage of the data?
To what map scale was the data digitised?
What projection, coordinate system, and datum were used?
What was the density of observations used for its compilation?
How accurate are positional and attribute features?
Does the data seem logical and consistent?
Is the data relevant to the project at hand?
In what format is the data kept?
How was the data checked?
Why was the data compiled?
What is the reliability of the provider?