GDM provides high-quality geographical information systems (GIS), digital mapping, photorevision, and cartography services in support of agencies' environmental programs. We provide a complete set of GIS services, from data acquisition, revision, and integration, to data analysis and visualization, application development, systems planning, and infrastructure counseling.

Founded in 1991, GDM is a small but growing company. We have four corporate offices located in Middleburg and Front Royal, Virginia, Stennis Space Center, Mississippi, and Austin, Texas. The GDM team has solid technical, production, and business backgrounds providing the versatility and depth necessary to be successful on large, technically complex mapping and GIS projects. We recruit qualified staff locally and nationally to meet the changing needs of projects and clients.

GeoDigital Mapping has been providing digital map products to a diverse user community. GDM is a principal contractor to the U.S. Geological Survey (USGS) for the creation of high-quality digital map products. Since 1992, GDM has been a certified USGS Digital Line Graph (DLG) contractor supporting the Rocky Mountain and Mid Continent Mapping Centers. In 1997, GDM established a unique arrangement with the USGS, creating an Innovative Partnership (IP) agreement with the USGS National Mapping Division to provide outreach to State and Federal agencies with interest in acquiring USGS digital map products not currently available. Through this IP, GDM is creating a multipurpose, statewide GIS database for the Texas Water Development Board.

GDM supports federal agencies in the use of GIS for environmental applications, from enterprise GIS for the Department of Transportation to on-site GIS and Remote Sensing technical support for the U.S. Forest Service to State and County-level watershed, wetlands, and storm water planning. GDM also develops mission critical products for the Department of Defense, Department of Transportation, Federal Emergency Management Agency, U.S. Forest Service, National Imagery and Mapping Agency, and the National Aeronautics and Space Administration. See our web site for a description of our projects and capabilities.

GDM categorizes its products and services into two areas described below: (1) Digital Mapping and Data Conversion Services, and (2) GIS Applications and Analysis Services.

DIGITAL MAPPING AND DATA CONVERSION SERVICES

GDM has extensive experience in all phases of GIS data production and update utilizing all forms of source materials, including existing digital data, aerial resource photography, hard copy resource maps, autocad drawings, stable-base Mylar and color separates. We specialize in format-to-format, projection, and datum conversions without loss of data quality or accuracy. We have extensive experience interpreting and producing all USGS digital products and we are able to support all digital products.

Computer facilities include 1600 dpi resolution binary and grayscale large document scanning and commercial GIS/CAD/Image Processing software (ArcInfo, ArcView, Microstation, ER Mapper, and Laser-Scan) operating in a high-end network PC environment. We are familiar with the programmatic, regulatory, and data management issues that government agencies face, and we translate priorities to appropriate and cost effective technical and management solutions.

Full-Feature USGS Digital Line Graph (DLG) Vector Data.

For over eight years, GDM has been a prime USGS contractor for the development of digital topographic maps for hydrography, topography, transportation, boundaries, vegetation, and other features useful for natural resource planning. The DLG Optional (DLG-O) format contains all attribute information and meets USGS specifications and quality assurance criteria. GDM employs production flow lines, high-end scanning, and both raster and vector edit technologies to produce the highest quality data in the shortest timeframes. Staying current with the latest capability requirements of the USGS, GDM has developed "digital revision" production capacity (described below) for the revision of older maps and GIS data sets based on newer photography or satellite imagery.

Orthophotograph-Based Digital Revision of DLG and Other Vector Formats.

GDM performs Digital Limited Updates or Photo-Revision of DLG and other vector data. Photorevised DLG is pre-requisite for the production of high-resolution National Hydrography Data (see below) used for natural resource planning, watershed analysis, and water quality modeling. Digital Limited Updates require the interpretation of Orthophotograph or high-resolution satellite imagery to update existing DLGs for accuracy and currency. Our procedures involve both aerial photography and Landsat TM imagery. Aspects of photo-revision include projection and datum conversion, aerial photo interpretation, revision of features, quality control attribution (such as changes to lake and shoreline boundaries), generation of topology, edgematching, generation of DLG-3 format, and QA and validation.

National Hydrography Data (NHD).

NHD is a spatial database that describes surface water features, flow direction, and their interrelationships. More and more, States and federal agencies are demanding NHD to support watershed analysis, water quality modeling, and national reporting of water data. As a nationally standardized database, the NHD provides a framework for linking water-related data from multiple sources to the surface drainage network. Through the NHD, information on flow rates, downstream risk potentials, environmental impacts and water quality may be integrated to enable advanced modeling and scientific analyses. GDM's NHD production includes the spatial accuracy, descriptive codes, and content comprehensiveness of USGS hydrography DLGs, unique stream IDs, USGS Geographic Names Information System (GNIS) naming conventions, and a linear referencing system.

Drainage-Enforced, High-Resolution Digital Elevation Models.

GDM produces Digital Elevation Models (DEM) at accelerated rates and at a competitive cost. GDM has a Commercial-Of-The-Shelf solution for building accurate DEM data consistent with USGS National Map Accuracy specifications. All DEM data produced under the GDM production process is validated with USGS-provided validation software modules. We produce both high (10 meter) and low (30 meter) resolution DEM data. The DEMs are "drainage-enforced" with high-resolution hydrographic vector data. Specific steps are taken to assure flow is not interrupted within a watershed and unnecessary sinks have been eliminated. The GDM quality control process also corrects for anomalies that often plague DEMs, such as abrupt breaks in elevation profiles, terracing, false depressions and sinks. These anomalies are corrected with both automatic and interactive procedures.

Large-Format B/W and Full Color Scanning.

GDM has been providing scanned data to its customers and to support its internal production activities since 1991. Our production capability consists of a large format ScanGraphics B/W and grayscale scanner (1000 dpi) and a large format, full color Vidar scanner (800 dpi). GDM scans clear film and color paper maps to support vectorization and DLG production. Photo-revision is supported with aerial photography. We also produce digital color separates from full color analog materials. As a standard practice, GDM scans all documents at a minimum of 800 - 1000 dpi resolution to ensure the greatest degree of positional accuracy and clarity of digital data.

GEOSPATIAL APPLICATIONS AND ANALYSIS SERVICES

GDM offers GIS and Remote Sensing data acquisition, data integration, and subject matter expertise to create innovative GIS solutions to assess and monitor the impact of man's activities on natural and cultural resources. In addition, GDM's highly experienced staff are familiar with the issues government agencies face in the areas of environmental planning, regulations, and technical support. With GDM's combination of technical and programmatic expertise, we can translate customer priorities to appropriate and cost effective technical solutions. Our GIS analysts and computer programmers develop GIS applications for most commercial platforms, including ESRI products (ArcInfo, ArcView, and ArcIMS) using AML and Avenue as well as other commercial programming languages (Visual Basic with MapObjects, C++, Delphi).

Below are a sample of our GIS Application and Analysis Services

Watershed Protection

Federal agencies in partnership with state and local governments are using watershed protections strategies to provide an integrated framework for natural resource management programs. These programs include wetlands protections, wastewater discharge permitting, flood control, drinking water protection, and wildlife management. GIS technology has been integral to successful implementation of these programs. GDM has experience applying the EPA approach to developing a Watershed Protection Strategy and implements the strategy by integrating local, regional, and national data to produce GIS Decision Support Tools. We integrate satellite data with local wetlands and land use information. This approach helps define and target priority problems affecting wetlands, mapping sensitive and endangered wildlife habitats, drinking water sources, sources of pollution, and fishery resources. Our methodology provides a comprehensive view of threats to human health and ecological integrity within specific watersheds.

Spatial Modeling for Environmental Health Risks

GDM implements county and regional models aimed at identifying environmental health risks. Spatial modeling can integrate diverse sources information to target key facilities, sensitive habitats, and sources of pollution. GIS is key For example, domestic and commercial septic systems are often poorly inventoried, and failing systems can pose microbial health risks to the community. GDM can locate and map households on public sewers and those with on-site sewage disposal systems and their proximity to wetlands, creeks, 100-year flood plains and other areas associated with risk to surface water resources. The information can provide health agency staff with the tools and information to prioritize inspection and permitting resources.

Support for Environmental Impact Assessments

The National Environmental Protection Act of 1969 (NEPA) has established a nationwide policy of promoting environmental consideration in Federal decision-making. Appropriate use of GIS can be cost-effective for feasibility and planning studies, establishing a monitoring network, and supporting public outreach and stakeholder involvement. GDM personnel have experience using GIS in environmental assessments and have experience in managing and participating in the multi-disciplinary teams often needed to adequately perform these assessments and impact statements.

Integration of Satellite Imagery to Support Storm Water Planning

GDM processes and integrates high resolution and low-cost satellite imagery with local data to identify "hot-spot" areas that contribute most to storm water problems. This approach estimates the extent of storm water impacts due to impervious surfaces and helps to target scarce resources for satisfying increasingly stringent federal regulations. GDM integrates digital layers of hydrography, watersheds, road features, political boundaries, parcel and zoning boundaries, and satellite-derived land cover. Increased impervious surface coverage can be a prime indicator of nonpoint source pollution and water quality degradation. We measure the impervious area in a town and compare it to a zoning-based buildout analysis to help highlight potential pollution problems. Zoning maps, local basins, and land cover information are combined to create the final images.

Land Cover Mapping from Satellite Imagery

Land cover datasets can be used for a wide variety of national and regional applications, including watershed management, environmental inventories, transportation modeling, fire risk assessment, and land-use planning and management. GDM Analysts use a variety of supporting information in addition to the satellite data, including topography, census, agricultural statistics, soil characteristics, other land cover maps, and wetlands data to determine and label the land cover type. We process Thematic Mapper imagery with a 30-meter pixel resolution and higher resolution SPOT and newer generation multispectral imagery. We also make use of recent USGS land cover mapping from the Multi-Resolution Land Characteristics project to obtain available land cover for the entire U.S.

Water Quality Protection

Increasingly, federal environmental managers are turning to information technology for efficient programmatic, policy and technical tools for protection water quality from point and nonpoint sources of pollution. GDM personnel have experience with water quality databases, regulatory requirements, and a variety of surface water and ground water models. This information is integrated using GIS as a common platform to support parameter input to models and to facilitate the interpretation of the model results. GDM personnel are familiar with water quality programs, including nonpoint source programs, TMDL, coastal protection programs, NPDES permitting, and watershed protection strategies. For example, GDM is supporting a project with the Mississippi Department of Marine Resources and the Navy's Gulf of Mexico Littoral Initiative to develop an approach for evaluating impacts to coastal fisheries from current and future land uses. The project will consider a number of parameters including nutrients, dissolved oxygen, fecal coliform, sedimentation, pesticides and herbicides, and heavy metals.

On-Site GIS Services

GDM can provide full-time or part-time support staff to meet a variety of GIS-related needs from complex data entry to GIS system development. Our staff is highly trained and closely supervised, relieving the client of many administrative requirements normally associated with short-term or intermittent work assignments. GDM on-site support personnel have a substantial background in all areas of GIS system development. GDM provides support staff for the US Forest Service and US Department of Transportation in the areas of cartographic map production, applications software development and other applications of GIS.

Internet Mapping Solutions

GDM offers affordable Internet mapping for clients that wish to add mapping and GIS query capabilities to their Web sites. We use and customize commercial software, such as ESRI Routemap and ArcIMS to produce interactive internet maps. We evaluate user requirements and internet performance issues and we recommend and implement appropriate servers, configurations, and hosting services.