Impervious Surface

The Impervious Surface raster layer represents impervious surfaces covering the Commonwealth of Massachusetts. The surfaces were extracted using semi-automated techniques by Sanborn Map Company from 50-cm Vexcel UltraCam near infrared orthoimagery that was acquired in April 2005 as part of the Color Ortho Imagery project. The pixel size for the impervious surface data is 1-meter. Impervious surfaces are defined as: * All constructed surfaces such as buildings, roads, parking lots, brick, asphalt, concrete. * Also included are areas of man-made compacted soil or material such as mining or unpaved parking lots (no vegetation present) Non-impervious surfaces can be defined as: * All vegetated areas, natural and man-made * Water bodies and wetland area * Ski runs * Natural occurring barren areas (i.e. rocky shores, sand, bare soil) Each category is listed in detail in Table 1 below. The dataset that MassGIS distributes also contains impervious surface pixels added by MassGIS that were created by buffering the EOT Roads layer. This process was done in order to fill in some breaks in roadway areas in the final Sanborn product delivered to MassGIS. This process is described in further detail below. Impervious surface pixels are identified with a value of 1. Non-impervious surface pixels have a value of 0. Stored in the ArcSDE, the statewide layer is named IMG_IMPERVIOUSSURFACE.

不透水面栅格图层（Impervious Surface raster layer）用于表征覆盖马萨诸塞联邦（Commonwealth of Massachusetts）的各类不透水面要素。该要素由桑伯恩地图公司（Sanborn Map Company）采用半自动化技术，从2005年4月获取的、作为彩色正射影像项目（Color Ortho Imagery project）组成部分的50厘米分辨率Vexcel UltraCam近红外正射影像（near infrared orthoimagery）中提取所得。本不透水面数据集的像素分辨率为1米。

不透水面的定义如下：
1. 所有人工构筑表面，包括建筑物、道路、停车场、砖块、沥青、混凝土等；
2. 各类人工压实土壤或物料区域，例如采矿场地或未铺装停车场（无植被覆盖）。

非不透水面的定义如下：
1. 所有植被覆盖区域，涵盖自然植被与人工植被区域；
2. 水体与湿地；
3. 滑雪道；
4. 自然裸露区域（如岩质岸滩、沙地、裸土）。

各类要素的详细分类见下文表1。

马萨诸塞州地理信息系统（MassGIS）所分发的本数据集还包含由该机构补充的不透水面像素：此类像素通过对EOT道路图层（EOT Roads layer）进行缓冲区分析生成，用于填补交付给马萨诸塞州地理信息系统的桑伯恩最终成果中道路区域存在的部分断点。该补充流程的详细说明见下文。

不透水面像素的像素值为1，非不透水面像素的像素值为0。本全州范围图层存储于ArcSDE中，图层名称为IMG_IMPERVIOUSSURFACE。