The type of insurance will generally depend on which countries you intend to operate in and your clients requirements.
In Australia, we have professional indemnity insurance which I am assuming is similar to omissions and errors insurance. There is also public and products liability insurance. Most insurers will package both into a single policy.
Also, GIS should fall into the IT classification. Make sure that your policy covers products and services - as there can be a blurred distinction between the two in the IT industry.
The best place to start would be talking to a local IT insurance broker as they would know the specific details for your area. Also, ask clients or potential clients what requirements they have regarding insurance coverage.
