There are likely to be gaps in the data for your town or city. You should try to fill these gaps by looking at grey literature (internal, unpublished reports) and conducting key informant interviews. Wherever possible, any data should be cross-checked (triangulated) with data from other sources. You will probably have to make assumptions about your city and town. When assumptions are made you should state clearly in the report the logic behind them. These assumptions should also be clearly explained in Section 7 of the Executive Summary (see SFD Report Template). By reviewing the reports from other cities you can see how other authors have overcome a lack of data.