zDocs Authoritative Topos and GeoChange Maps

Authoritative US Topos and GeoChange Maps

Hyper-accurately imaged USGS Topographic 7.5 minute Quadrangles were created to update the original DRGs produced in the late 1990s. The new scanning technology, designed for geometric accuracy such that GIS data can be created from paper maps, in addition to image processing techniques, has created a new product that has more features than improved resolution and line acuity. Color correction and whitening of the background (paper without print in hard copy form) allows the data encapsulated in these files to be combined through transparancy techniques with other datasets, including modern aerial photography to show two slices of time in one image. Using the Authoritative US Topos with modern imagery has been created for the nation as a series called Authoritative US Topos GeoChange Maps which have been published as GeoPDFs for use with mobile devices, and are currently for sale on Avenza’s PDF Map App. Authoritative US Topos are also available in the mobile app, as GeoTIFF desktop GIS products, and for custom print through MapSherpa.

Dataset Basics

USGS has over 100 years of Ground Truthing Built into the Dataset

– Moving this data up to today’s standards for digital rasters

– Bridging the Gap between Paper and Digital

– Accurate rasters for use offline with GPS in field data collection

– Historical data for use with modern imagery for instant change detection

– Maps and Imagery combined have the mutual benefit of improved interpretation

– Whitened and Color Convergent

 – Prime inputs for development path of Feature Extraction and Vectorization

– Contiguous National Symbology

– Standardized level of accuracy across all states

– Approximately 57,000 map sheets (65,000 including Alaska)

About USGS DRGs

Produced from 1995-1998 by USGS and Land Information Technology Company Ltd with the objective of scanning all quads quickly and at low cost (largely due to the expensive nature of digital storage at that time).

– US Topos are 7.5-minute quadrangle 250 dpi GeoTiff maps

– 60 sqmi covered by a quad on average (66 sqmi in south TX to 49 sqmi in north MN)

– Tigerline files and the National Elevation Dataset were created from DRGs

– Surveying began in 1884, and field checked up until WWII updates from air photos

– USGS ‘crowd-sourced’ data in the 1980s called Earth Sciences Volunteers

– Tiff-remap software forced color palate into 13 colors, and resulted in line aliasing

About Authoritative US Topos and GeoChange Maps

Produced from 2009-2014 by The W.E. Upjohn Center for the Study of Geographical Change with the objective to scan all quads accurately and in high quality and ultimately produce 250 dpi GeoTiff and 250 dpi GeoPDF products.

– Scanning technology designed to produce GIS data from paper maps.

-Purchased 65,000 paper maps from Land Info Tech (same paper maps used for DRGs)

– 1:24,000 scale digital topos line up impeccably with 1:12,000 scale imagery.

-Largely due to USGS field surveying and quality standards

– Authoritative US Topos and GeoChange maps = 57,000 x 2 = 114,000 GeoPDFs

-57,000 GeoTiffs and 57,000 NAIP clip GeoTiffs = 114,000 GeoTiffs

-Totaling 228,000 maps

Tutorials for Geoprocessing a Major Map Dataset

Outline of the full process

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