8000 - Laserfiche WebLink

Home Browse Search

Dr. Julia Graf, USGS, Tucson, Arizona, provided side-scan sonar bed material data as a means to test historic hard copy map data. The sonar data presented these obstacles: 1. The data were available only in hard copy format. 2. The data were graphically linear and thus did not conform to the river channel. 3. The data represented a flow regime of 25,000 ft3/s, not the 5,000 ft3/s scientific flow represented by the base map products. 4. The data had no monumented registration points other than the 1923 USGS river mileage at 1/10-mile increments in the center of the river. The side-scan sonar data were scan digitized and converted into ARC/INFO format. Using the 1923 river mileage points as a standard, common tics were generated for both coverages. The linear side-scan sonar data were georeferenced using a transformation function, and conformed to the 1990 river mileage coverage by using the established registration points and rubber sheeting. The exercise in integrating historic data proved that it is possible to bring most georeferenced data into the GCES/GIS. The exercise highlighted the need for metadata for both historic and current data sets. The absence of metadata would prevent any determination of the accuracy or validity of data being used in the GCES/GIS data base. The potential size of the GCES/GIS data base warrants the use of established metadata standards. The GCES SIM program is currently forming a task group to develop metadata standards to be used with all contributed data sets. The intention of the task group is to follow the FGDC (Federal Geographic Data Committee) draft report on "Content Standards for Spatial Metadata" as closely as possible to ease the transition from our metadata standards to the FGDC standards once they have been finalized. The pilot study prompted the Remote Sensing and Geographic Information Section to develop a classification scheme to be used in the mapping effort. The final data base will be provided by the respective GCES and/or cooperative specialist. In the interim, the staff of the Remote Sensing and Geographic Information Section will categorize resources to promote continuing development of the data base. The purpose of the classification scheme is to identify natural and cultural features that are important to long term monitoring of the river environment. Features such as new and old high water vegetation, cobble bars, riffles, and side channels are included in the classification scheme. The categories in the classification scheme and their responsible contributing organization are shown in appendix B. Class definitions that were used by the Reclamation Remote Sensing and Geographic Information Section in the collection of their data can be found in appendix C. 12