GARBAGE IN GARBAGE OUT: This is one of the most famous acronyms in the history of computing. What this means is that it doesn’t matter if you have the most brilliant software and hardware: if your data is rubbish then your outputs or analysis will be rubbish as well. When I am working with data, particularly migrating or loading data between systems I check the accuracy of that data as part of the process (rather than loading it and then trying to work out why I am getting strange results later).
GIS data requires many more checks compared to standard ‘text and numbers’ data so I recommend working through a checklist of tests as I have provided in the list below. It should be noted that different GIS/CAD etc software has different rules for things like how topology works. The following list is slightly targeted towards ArcGIS but should also provide some hints for users of other GIS/CAD software: https://www.linkedin.com/pulse/gis-gigo-garbage-out-30-checks-data-errors-nathan-heazlewood?