USDA Soils

The Soils datalayer has been automated from published soils surveys as provided on various media by the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS). All soils data released by MassGIS have been "SSURGO-certified," which means they have been reviewed and approved by the NRCS and meet all standards and requirements for inclusion in the national release of county-level digital soils data. Soil survey areas are roughly based on county boundaries. The SSURGO-certified soils dataset is generally the most detailed level of soil geographic data developed by the National Cooperative Soil Survey. The information was prepared by digitizing maps, by compiling information onto a planimetric correct base and digitizing, or by revising digitized maps using remotely sensed and other information. The data include a detailed, field verified inventory of soils and miscellaneous areas that normally occur in a repeatable pattern on the landscape and that can be cartographically shown at the scale mapped. Data for survey areas were developed using various scale base maps: some areas at a 1:25,000 or 1:12,000 scale, or at larger scales where source materials (e.g. 1:5,000 MassGIS ortho imagery) were available. Details for a specific survey area are provided in the NRCS-produced metadata that are distributed with the spatial data. The soil map units are linked to attributes in the National Soil Information System (NASIS) relational database, which gives the proportionate extent of the component soils and their properties. At MassGIS the soils datalayer is stored in ArcSDE for Oracle as the statewide feature class SOILS_POLY. Two companion layers, SOILSPOT_PT and SOILSPOT_ARC, represent "special" or "ad hoc" features such as gravel pits, wet areas, bedrock escarpments and others. These layers display the location of features too small to delineate at the mapping scale, but they are large enough and contrasting enough to significantly influence use and management. The status for each survey area is stored in the statewide layer named SOILSTAT_POLY. See details in the Entity Attributes section. The soils polygons were updated in August 2010 for new data for Plymouth. Also, the adjacent survey areas (Barnstable, Bristol North, Bristol South, and Norfolk-Suffolk) were replaced, as these were edited to edge-match with Plymouth. With the August 2010 update, soils data are available for all survey areas in the state except for Franklin, which is under development.本土壤数据层由美国农业部（United States Department of Agriculture, USDA）自然资源保护服务局（Natural Resources Conservation Service, NRCS）以多种介质发布的已公开土壤调查成果自动化构建而成。马萨诸塞州地理信息系统（MassGIS）发布的所有土壤数据均为SSURGO认证（SSURGO-certified）数据，即此类数据已通过NRCS的审核与批准，符合国家级县级数字土壤数据发布的全部标准与要求。土壤调查区域大致以县级行政边界为划分依据。经SSURGO认证的土壤数据集通常是国家合作土壤调查（National Cooperative Soil Survey）项目产出的精度最高的土壤地理数据。该数据集通过以下方式制作：对地图进行数字化、将信息整合至平面校正基准底图后数字化，或是利用遥感及其他信息对数字化地图进行修订。数据包含经野外验证的详细土壤与杂类区域清单，此类要素在地表通常以可重复的分布模式出现，且可按成图比例尺进行制图表达。不同调查区域的数据基于不同比例尺的底图制作：部分区域采用1:25000或1:12000比例尺，若有原始资料（如1:5000比例尺的MassGIS正射影像）则可采用更大比例尺。各调查区域的详细信息可随空间数据一同分发的、由NRCS编制的元数据中获取。土壤制图单元与国家土壤信息系统（National Soil Information System, NASIS）关系型数据库中的属性相关联，该数据库可提供各组成土壤的占比范围及其属性特征。在MassGIS平台中，本土壤数据层以全州要素类SOILS_POLY的形式存储于面向Oracle的空间数据引擎（ArcSDE）中。配套的两个图层SOILSPOT_PT与SOILSPOT_ARC用于表示"特殊"或特设（ad hoc）要素，例如砾石坑、湿地、基岩陡崖等。此类要素在成图比例尺下因尺寸过小无法单独勾绘，但其规模与特征对比度足以对土地利用与管理产生显著影响，因此通过上述图层标注其位置。各调查区域的状态信息存储于名为SOILSTAT_POLY的全州图层中，详细信息可参见要素属性章节。本土壤多边形数据集于2010年8月针对普利茅斯（Plymouth）区域的新数据完成更新；同时，与其相邻的巴恩斯特布尔、北布里斯托尔、南布里斯托尔以及诺福克-萨福克等调查区域也完成了数据替换，以确保其制图边界与普利茅斯区域完全匹配。经2010年8月的此次更新后，全州除富兰克林（Franklin）区域外的所有调查区域均已可获取土壤数据，富兰克林区域的数据仍在开发中。