As various sites are being investigated and especially after one has been selected, land surveyors may be engaged. For building projects, this work includes investigation of property records, easements and rights of way, establishment or re-establishment of property corners and boundaries, determination of land contours and slopes and location of existing improvements, natural features and obstructions. A pipeline or highway project can involve much preliminary route layout as various alternative routes are investigated. This effort includes on-the-ground, aerial/photogrammetric and satellite-based global positioning system methods that lead to route layouts, various kinds of maps and geographic information system databases for use in project planning. Surveyors may also be involved in the construction phase, but they are equally important as part of the planning and design team.