Buildings

The building footprint layers shows the area of buildings. Since 2001, most buildings have been GPS'd, typically within an accuracy of three feet. Some of the buildings footprints before 2001 have been updated and/or adjusted with aerial imagery. Some of the commercial building footprints have been created or adjusted using contruction plans.建筑轮廓图层（building footprint layers）用于呈现建筑物的占地面积范围。自2001年起，绝大多数建筑物已通过GPS测绘，定位精度通常可达3英尺。2001年之前的部分建筑轮廓已通过航空影像完成更新与修正。部分商业建筑轮廓则依托建筑施工图纸完成创建或修正。