Alabama Statewide Digital Ortho-photography and LIDAR Mapping Project Introduction Recent years have seen the purchase of an increasing number of LIDAR surveys and digital ortho-photography by municipalities and public agencies in Alabama. Uses for the data include Economic Development, Parcel Mapping, Emergency Planning, Flood Map Modernization, Geologic Mapping, ground-water modeling and management, Highway Planning, and Urban and Suburban Infrastructure Engineering. A single statewide program can be managed and implemented for far less money than state and local governments spend when they issue independent contracts. This program will offer outstanding value to local governments through price breaks achieved through volume (area) discounts. This main objective of the program will be the creation and establishment of a consistent, accurate, foundational base map upon which local government and many regional, state and federal geospatial data applications could be built, working towards producing an efficient statewide spatial data infrastructure. Aerial imagery is the foundation for most public and private GIS (Geographic Information Systems) operations, yet it is being developed by many different entities across Alabama in an uncoordinated fashion. Some areas are essentially “left behind” due to lack of coordination or funding. There are holes in the coverage, varying qualities of product and the duplication of effort leads to higher costs; varying quality, accuracy and age along with restrictions on its access and use. This program will ensure the widest utility of digital ortho-photography and elevation data for the user and producer communities through enhanced data sharing and the reduction of redundant data production. The goals of this project are; - Acquire 1”=200’ color and color infrared digital ortho-photography statewide - Acquire two foot contour data statewide collected and processed to meet specifications called for in FEMA’s Guidelines and Specifications for Flood Hazard Mapping Partners. - Establish a Statewide Mapping Program for the perpetual maintenance of this data set. This plan has been developed based on the findings of the AlabamaView Consortium which are described in the Statewide Digital Orthophoto Fly Plan for the State of Alabama report. This document outlines the projected benefits and cost savings of acquiring data on a statewide basis as well as proposes the methods by which to develop such a program. Specifications The first task for this project will be to develop a common specification for public agency digital ortho-photography and LIDAR surveys acquisition. A common specification will ease the writing of acquisition contracts, facilitate the sharing of data across agencies, increase the overall usability of the data, and minimize cost to the public. While these type acquisitions can be designed for different resolutions, accuracies, and costs to meet particular needs, the likely benefits from acquisition of data suitable for multiple uses far outweigh any short-term savings from acquisitions of less accurate or lower resolution data. Geodetic Foundations The key component to any successful remote sensed data acquisition is the supporting geodetic network used to control horizontal and vertical positioning. In 1994, work was completed on the first order horizontal control network established on a six mile grid throughout the state. The update of this system began through the Alabama Height Modernization Project by establishing a network of high order horizontal marks with high order elevations in 2004. The Alabama Continuously Operating Reference Station Network currently under construction will complete the required geodetic framework to support all phases of the project. This Geodetic Foundation will ensure that all data is collected to the accuracy required and is appropriately tied to the National Spatial Reference System (NSRS) while providing the cost savings over conventionally controlled mapping projects. Digital Ortho-Photography Digital Ortho-Imagery provides the visual content of an aerial photograph while being as accurate as a map for measurements. These qualities allow users to easily: - Measure Distance - Calculate Areas - Determine Shapes of Features - Calculate Directions - Determine Accurate Coordinates (Locations) - Determine Land Cover & Use - Perform Change Detection Ortho-photography is displayed in E-911 response centers to dispatch first responders to exact locations and for tracking incoming calls from mobile phones. Police in squad cars and rescue workers in fire trucks analyze ortho-photography before responding to emergencies. Digital images are used to collect a wide variety of information, including transportation routes, wetlands, streams, shorelines, building outlines, timber stands, land use patterns, farm fields, and crop types. Local governments rely on ortho-photography to map land property boundaries and to manage their streets and other infrastructure assets. Ortho-photography serves as a seamless base map layer to which many other layers are registered. It provides visual information for the following partial list of applications. - Homeland Security, Homeland Defense & Emergency Management - Economic Development - Public Safety Planning, Response & Mitigation - Tax Parcel Mapping - Transportation Management, Operations & Planning - Utilities Management, Operations & Planning - Land Planning and Zoning - Drainage Planning & Management - Code & Permit Enforcement - Agriculture - Insurance - Surveying & Mapping - Environmental Management, Planning & Regulation - Education - Natural Resource Inventories and Assessments LIDAR (Light Detection and Ranging) LIDAR is a technology that employs an airborne scanning laser rangefinder to produce detailed and accurate topographic surveys. LIDAR can be used to accurately measure the topography of the ground, even where overlying vegetation is quite dense. As the technology has matured, and the analysis and utilization of the entire LIDAR signal has improved and increased, utilizations of the entire dataset and not simply bare earth derivatives have developed dramatically. LIDAR data are being utilized extensively in the forestry and ecology realms, and the new uses are being demonstrated in feature extraction of man-made structures in urban settings for building delineations and emergency response and homeland security purposes. The opportunity to begin collecting LIDAR data is quite advantageous to the Program. In evaluating various options for LIDAR collection and processing, it became apparent that there would be significant synergies in combining the ortho- photography and LIDAR efforts. Evaluation of labor costs for each individual phase of the work confirmed substantial cost and workflow savings could be realized by combining efforts. The Digital Elevation Model (DEM) compiled from the LIDAR will replace the labor required to generate the DEM to support the imagery. In addition, utilizing the CORS network for Air Borne GPS for each phase of the project will dramatically reduce the amount of ground control required to support the project. Summary of Project Specifications Orthophoto Terrestrial LiDAR (2 ft surface) (1”=200’) Horizontal 7.6-foot horizontal 3.8-foot horizontal accuracy (2.2 foot RMSE) Accuracy accuracy (4.4 foot RMSE) Vertical Based upon digital 0.6-foot fundamental vertical accuracy Accuracy elevation model Projection Alabama State Plane Alabama State Plane US Feet Survey US Survey Feet NAD83(NSRS2007) NAD83 (NSRS2007) Adjustment Datum NAD 83 (NSRS2007) NAVD 88 (based upon latest Geoid) Post- 1 foot 4 foot spacing / pixel size Format TIFF uncompressed LAS 1.1 Natural Color and Color Infrared Flight Leaf-off Leaf-off Season Breaklines Hydrologically correct breaklines Metadata FGDC Contours Two foot LAS 1.1 Class1, Class 2, Class 7, Class 9, and Class (ASPRS) 12 Local County and City Participation County and city government may have certain needs for mapping products above and beyond the scope described in this document. These needs may include some or all of the following: - 0.5’ resolution imagery - Building footprints - Road Centerlines - Pavement edges - Impervious features - Visible Utilities - Any other photo-identifiable feature which can be collected in a vector format. County and city governments will be given the option to “buy-up” to these options with the pricing based on the level of effort above and beyond the initial acquisition by the state. Additional feature capture or resolution enhancement on behalf of governmental entities for deliverables other than those identified in the Contract will require a separate agreement between the successful Contractor and participating counties, municipalities, or State agencies. Long Term Update and Maintenance As with any remote sensed data, the original acquisition data will have a “shelf-life” or a period of usefulness. As development and growth continue in Alabama, updates for these data sets at regular intervals will be an important component of the project. This project will bring together a group of partners and stakeholders with a shared interest in developing and maintaining a program to support the perpetual maintenance of the data sets. Cost of the Proposal The State estimates that a statewide program will cost approximately $15 million for the initial acquisition of imagery and LIDAR data. The maintenance costs are estimated at approximately $1.3 million per year based on industry pricing. Conclusion The State of Alabama has the unique opportunity to leverage existing partnerships, programs, and funding for the initial acquisition of a reliable, up to date, ortho- photography and LIDAR base map. The justification for this project is simple: Due to the economy of scale, the State of Alabama will spend less money acquiring this comprehensive data set, than the sum of all of the individual projects over the same time period which will still not produce an overall, complete map of the state. The added long term benefits derived from the creation of a state map, improved data quality, standards and practices for data sharing, and community building will greatly enhance the state’s ability to manage its resources and provide the citizens of Alabama efficient government services.
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