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In spring 2013, the U.S. Geological Survey contracted for true-color imagery covering three urban areas in Massachusetts as defined by the USGS. Those areas are the metropolitan Boston area (and beyond), the greater Worcester area, and the greater Springfield area. Image type for all of the areas is 24 bit, 4-band (red, green, blue, and near-infrared RGBN) portions of the spectrum. Each band has pixel values ranging 0-255. Pixel resolution is 0.3 meters (30 centimeters), or approximately one foot.
This digital orthoimagery can serve a variety of purposes, from general planning, to field reference for spatial analysis, to a tool for data development and revision of vector maps. It can also serve as a reference layer or basemap for myriad applications inside geographic information system (GIS) software.
It was created to provide easily accessible geospatial data which is readily available to enhance the capability of Federal, State, and local emergency responders, as well as plan for homeland security efforts. These data also support The National Map.
The raw ADS80 image data were collected by Fugro EarthData, Inc. at about 2,896 meters above mean terrain during mid to late April 2013. The source imagery is cloud free, and was acquired in generally leaf-off conditions.
TerraSurv, Inc. was contracted by Fugro to provide ground control survey to support photogrammetric mapping and blind QC points. The National Spatial Reference System (NSRS) was used to provide control for the network. The KeyNetGPS Virtual Reference System (VRS) service was used to georeference each station. This VRS network is consistent with the National CORS at the centimeter level. The horizontal datum was the North American Datum of 1983 (2011), and the vertical datum was the North American Vertical Datum of 1988. The GEOID12A model was used.
Spatial Data Quality - Horizontal Positional Accuracy
The design accuracy is estimated not to exceed 1.52-meters NSSDA 95% confidence (0.88-meters Root Mean Squared Error (RMSE)) XY (0.62 meter RMSE X or Y). The Horizontal Positional Accuracy Values are 0.50 meters (Boston-Providence and Worcester) and 0.52 meters (Springfield). These are estimates of the accuracy of the horizontal coordinate measurements in the datasets derived using the Federal Geographic Data Committee, 1998, Geospatial Positioning Accuracy Standard, Part 3, National Standard for Spatial Data Accuracy, FGDC-STD-007.3-1998. Detailed accuracy reports were delivered to MassGIS.
Each orthoimage tile provides imagery over a 1500-meters by 1500-meters block on the ground. There is no image overlap between adjacent tiles in a footprint. The Worcester Footprint overlaps the Boston footprint (although this overlap was removed for distribution by MassGIS). While dozens of tiles for New Hampshire and the open ocean were delivered by USGS, MassGIS is not distributing them here. A small portion of southeast Duxbury Beach (affecting territory in both Duxbury and Plymouth) was not flown.The final digital ortho product delivered to MassGIS was a set of GeoTIFF files. The coordinate systems for the data are UTM Zone 19N for the Boston and Worcester areas, and UTM Zone 18N for Springfield, all referenced to the NAD83 datum.
The tile naming convention is based on the U.S. National Grid (USNG), taking the coordinates of the southwest corner of the orthoimage.
The following software was used for validation of the imagery and surface modeling: Pixel Factory 3.2, Linux; Bentley MicroStation; ESRI's ArcMap; ERDAS Imagine; TerraScan/TerraModel; SimActive Correlator3D; Fugro EarthData proprietary software; Adobe Photoshop; and GPro.
The Pixel Factory process was used in the generation of the orthoimagery covering all project tiles. An autocorrelated surface was generated to support the development of the orthophotography. This surface was edited into a bare earth digital elevation model (DEM) for use in orthorectification. The rectification process was then run using the processed digital surface model (DSM) on each flight line.
A "quicklook" (reduced resolution rectification) of each flight line was exported out of Pixel Factory. Radiometric adjustments were made to the quicklooks using Fugro proprietary tools. Radiometry was verified by visual inspection of the digital orthophoto. Slight systematic radiometric differences may exist between adjacent orthoimage files; these are due primarily to differences in source image capture dates and sun angles along flight lines. These differences can be observed in an image's general lightness or darkness when it is compared to adjacent orthoimages.
Tonal balancing may have been performed over a group of images during the mosaicking process, which served to lighten or darken adjacent images for better color tone matching. The radiometrically balanced imagery was then re-imported into the Pixel Factory system and the histogram from the quicklook was applied to the full resolution imagery.
Mosaic lines were placed, joining the ADS80 imagery strips. An initial QA/QC was performed by a technician to ensure that the mosaic lines were appropriately placed and that there was appropriate imagery coverage. Seamline mismatches were not corrected unless the overall displacement exceeded 0.6 meters. Orthoimages were visually inspected for completeness to ensure that no gaps or image misplacements existed within and between adjacent images.
The final imagery data set was removed from the Pixel Factory environment in a process called "packaging", where the individual tiles were created. All data processing in the Pixel Factory system was performed in UTM Zone 18N or 19N meters; it was during packaging that final datum and projection were defined.
The tiles were reviewed to ensure the output was successful and ground control points were measured and verified for accuracy. QA/QC was performed to look for anomalies, smears and other indications of problems within the digital orthophoto creation process, and interactive radiometric adjustment was applied where needed. Additional global radiometric adjustments were applied to the completed orthos in Adobe Photoshop to enhance the color and/or contrast as needed.
All GeoTIFF tagged data and image file sizes were validated using commercial GIS software to ensure proper loading before being archived. This validation procedure ensured correct physical format and field values for tagged elements. The final digital ortho products were delivered to USGS in GeoTIFF format by the end of June.
As requested by the Mass. Executive Office of Public Safety, MassGIS "deresolved" (blurred) the imagery in a few areas for security reasons.
Because of the large size of the GeoTIFFs, MassGIS is making these images available for free download in the compressed JPEG 2000 format. Users may order compressed mosaics or original data on DVD or hard drive.
Images are available for download in the JPEG2000 format, at a 20:1 compression ratio, 4 bands (RGBN), as 1,500 meters × 1,500 meters tiles.
How to Download:
- Open OLIVER and use the Identify tools to select your area of interest.
- A popup box will display the link for each tile you selected. Click on each link to download a .zip file.
- To download many images in a more automated way, click the 'Save all records as' dropdown and save to an Excel file. Then:
- Open Excel, copy only the cells with the links and paste them into Notepad or other text editor and save as a text file.
- Download the free WinWGet software and load the text file into a new job. Run the job and all the zipped images will be downloaded to a folder you choose.
See detailed instructions (PDF) on the download process file size 1MB .
Go to the MassGIS Online Order Form and choose Digital Data Products > 2013 USGS Color Ortho Images.
On user-provided hard drive:
- The uncompressed 1,500m x 1.500m GeoTIFF tiles, 30cm resolution (4-band RGB, 95 MB each) each with an RRD and AUX file
- Regional MrSID mosaics 3 bands (RGB) created from the 0.3 meter GeoTIFF imagery (compression ratio 30:1) Please see COQ2013MOSAICS30CM_POLY for the index shapefile. We anticipate a 2014 flyover will complete the State, thus the non-sequential tiling scheme.
Displaying the images
For ArcGIS Desktop users, to facilitate the display and management of multiple images, load the downloaded data into an unmanaged Raster Catalog inside a File Geodatabase, then add the Raster Catalog into ArcMap. With this approach, you will have only one item (the Catalog) in your table of contents.
What to do after downloading the JP2 data:
- Download the zipped file geodatabase MassGIS has prepared, containing two Raster Catalogs (for use in ArcGIS 9.3 and above)
- Unzip the download
- In ArcCatalog, go into the file geodatabase and right-click the raster catalogs (one for Boston/Worcester area imagery in UTM Zone 19N and one for Springfield area imagery in UTM Zone 18N) and choose Load.
See the Raster Catalog Instructions for illustrated details.
The datalayer is produced and maintained by the USGS Earth Resources Observation and Science Center in Sioux City, SD.
U.S. Geological Survey
EROS Data Center
47914 252nd Street
Sioux Falls,SD 57198-0001
HOURS: Monday through Friday 8:00 AM to 4:00 PM (Central Time)
Additional information concerning the technical details of the project may be available upon request.
Last Updated 1/23/2013