When do I need a property survey

The question should be asked more often, but isn't.
A survey should be ordered when:
Any land is purchased,
Before land is sold,
Prior to any activity near a lot line such as fence construction or planting,
Prior to, during and/or after any utility modifications near a property line,
Prior to, during and or after any neighbors activities that may affect your property rights,
Prior to, during or after and street improvements.
When neighbors land is for sale or changes ownership.
When refinancing property.
Prior to and sometimes after additions added to a house or building.
These are some of the most common times but if you have any uncertainty to your property line location have it surveyed!

The rules governing land surveying in Wisconsin

http://www.legis.state.wi.us/rsb/code/a-e/a-e.html

Land Surveying

"Land Surveying" is the detailed study or inspection, as by gathering information through observations, measurements in the field, research of legal instruments, and data analysis in the support of planning, designing, and establishing of property boundaries. It involves the re-establishment of surveys and boundaries based on documents of record and physical evidence, as well as subdivision of land.
Land surveying can include associated services such as mapping and related data accumulation, construction layout surveys, precision measurements of length, angle, elevation, area, and volume, as well as horizontal and vertical control surveys, and the analysis and utilization of land survey data.