Loudoun Soils

More Metadata Abstract: The general soil association map outlines broad areas which have distinctive patterns in landscape and general geographic appearance. Each of the soil associations has a unique set of features which effect general use and management including shape and length of slope; width of ridgetops and valleys; frequency, size, and direction of streams; type of vegetation, rate of growth; and agriculture. These differences are largely the result of broad differences in kinds of soils and in the geologic materials from which the soils formed. A mapping unit typically consists of one or more major soils with minor soils, and is named for the major soils. This map shows, in small scale, a summary of the information contained on the individual detailed soil maps for Loudoun County. Because of its small scale and general soil descriptions, it is not suitable for planning small areas or specific sites, but it does present a general picture of soils in the County, and can show large areas generally suited to a particular kind of agriculture or other special land use. For more detailed and specific soils information, please refer to the detailed soils maps and other information available from the County Soil Scientist. Digital data consists of mapping units of the various soil types found in Loudoun County, Virginia. The data were collected by digitizing manuscript maps derived from USDA soil maps and supplemented by both field work and geological data. Field work for the soil survey was first conducted between 1947 and 1952. Soils were originally shown at the scale of 1:15840 and then redrafted by the County soil scientist to 1:12000; the data were redrafted a final time to fit Loudoun County's base map standard of 1:2400. Although the current data rely heavily on the original soil survey, there have been extensive field checks and alterations to the soil map based on current soil concepts and land use. The data are updated as field site inspections or interpretation changes occur. Purpose: Digital data are used to identify the mapping unit potential for a variety of uses, such as agriculture drainfield suitability, construction concerns, or development possibility. This material is intended for planning purposes, as well as to alert the reader to the broad range of conditions, problems, and use potential for each mapping unit. The mapping unit potential use rating refers to the overall combination of soil properties and landscape conditions. The information in this data set will enable the user to determine the distribution and extent of various classes of soil and generally, the types of problems which may be anticipated. HOW NOT TO USE THIS INFORMATION The information in this guide is NOT intended for use in determining specific use or suitability of soils for a particular site. It is of utmost importance that the reader understand that the information is geared to mapping unit potential and not to specific site suitability. An intensive on-site evaluation should be made to verify the soils map and determine the soil/site suitability for the specific use of a parcel. The original Soil Survey was written for agricultural purposes, but the emphasis has shifted to include urban/suburban uses. The Revised Soil Survey is currently under technical review and is expected to be published by 2006. Supplemental information: The Interpretive Guide to the Use of Soils Maps; Loudoun County, Virginia contains more detailed soils information. Data are stored in the corporate GIS Geodatabase as a polygon feature class. The coordinate system is Virginia State Plane (North), Zone 4501, datum NAD83 HARN.

更多元数据摘要：通用土壤组合图(general soil association map)勾勒出在景观与整体地理外观上具备独特格局的广阔区域。每一类土壤组合均拥有一组独特特征，这些特征会影响其通用用途与管理方式，包括斜坡的形态与长度、山脊与山谷的宽度、溪流的出现频率、规模与流向、植被类型与生长速率，以及农业利用情况。这些差异本质上源于土壤类型及其成土母质的广泛差异。制图单元(mapping unit)通常由一种或多种主要土壤及少量次要土壤构成，并以主要土壤命名。本图以小比例尺汇总了弗吉尼亚州劳登县(Loudoun County)各详细土壤图的信息。由于其比例尺较小且仅提供通用土壤描述，该图不适用于小区域或特定地块的规划，但可呈现该县土壤的整体概况，并能显示大致适合特定农业类型或其他特殊土地利用的大片区域。如需获取更详细、具体的土壤信息，请查阅县土壤专家提供的详细土壤图及其他相关资料。
数字数据包含劳登县境内各类土壤类型的制图单元。该数据通过将源自美国农业部(USDA)土壤图的手绘原稿地图进行数字化采集而成，并辅以野外调查与地质数据。本次土壤调查的野外工作最初于1947年至1952年间开展。土壤信息最初以1:15840的比例尺绘制，随后由县土壤专家重新编绘为1:12000比例尺；最终数据再次进行编绘，以符合劳登县1:2400的底图标准。尽管当前数据大量依托原始土壤调查成果，但已基于现行土壤学理念与土地利用情况开展了大量野外核查与图件修订。该数据会根据野外实地勘查结果或解译变更情况进行更新。
用途说明：数字数据可用于识别各类场景下的制图单元适宜潜力，例如农业排水场适宜性(drainfield suitability)、施工相关考量或开发可行性。本数据用于规划工作，同时可帮助使用者了解各制图单元所涉及的各类条件、潜在问题与利用潜力。制图单元的潜在用途评级是土壤属性与景观条件的综合体现。本数据集可帮助使用者确定各类土壤的分布范围与覆盖面积，同时大致预判可能出现的各类问题。
不当使用须知：本指南中的信息不可用于判定特定地块的土壤具体用途或适宜性。使用者务必明确：本数据针对的是制图单元的整体潜力，而非特定地块的适宜性。需开展深入的现场评估，以验证土壤图的准确性，并确定某一地块特定用途下的土壤/场地适宜性。原始土壤调查最初专为农业用途编制，但当前已拓展至涵盖城市/郊区土地利用场景。修订版土壤调查目前正处于技术审核阶段，预计将于2006年发布。
补充说明：《弗吉尼亚州劳登县土壤图使用解读指南》包含更详细的土壤信息。数据以面要素类(polygon feature class)的形式存储于企业级地理信息系统地理数据库(GIS Geodatabase)中。坐标系采用弗吉尼亚州平面坐标系(Virginia State Plane (North))，分区4501，基准面为NAD83 HARN(datum NAD83 HARN)。