@article{,
title = {Massachusetts 1:5,000 Color Ortho Imagery (2005) - JPEG 2000 Format (Original)},
journal = {},
author = {MassGIS },
year = {},
url = {},
abstract = {Overview

These medium resolution true color images are considered the new "basemap" for the Commonwealth by MassGIS. The photography for the entire commonwealth was captured in April 2005 when deciduous trees were mostly bare and the ground was generally free of snow.

Image type is 4-band (RGBN) natural color (Red, Green, Blue) and Near infrared in 8 bits (values ranging 0-255) per band format. Image horizontal accuracy is +/-3 meters at the 95% confidence level at the nominal scale of 1:5,000. This digital orthoimagery can serve a variety of purposes, from general planning, to field reference for spatial analysis, to a tool for 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. The project was funded by the Executive Office of Environmental Affairs, the Department of Environmental Protection, the Massachusetts Highway Department, and the Department of Public Health..

Production
Sanborn LLC of Colorado Springs, CO, performed all work for this project. The source imagery was acquired with a Vexcel Ultracam digital camera at a flying height of 5,070 meters above mean terrain and an approximate pixel resolution of 45 cm.

Forward overlap was approximately 60%, except 80% in areas with tall structures (downtown Boston, Worcester, and Springfield), in order to reduce building lean, with sidelap of 33%. The entire state was covered by about 5500 image frames, captured over seven days from April 9 through April 17, 2005.

The ground control used to support the mapping was collected by photographic identification of strategic points. The ground control coordinates were collected via GPS ground survey techniques. Aerial Triangulation was performed on softcopy workstations using Intergraph ISAT software for photo measurement and matching. The final bundle adjustment was performed using BINGO 5.2 software.

A new digital elevation model was stereo compiled for the entire State from the newly acquired 2005 imagery. The DTM includes mass points, soft breaklines and hard breaklines. The images were ortho-rectified using METRO, Sanborn's proprietary software. Bridges were modeled in 3-D using standard photogrammetric stereo-compilation techniques on softcopy workstations. Sanborn's Metro process rectifies the bridges using the 3-Dimensional model using similar methodologies for correcting the positional accuracy of other ground features. The bridges were uniquely coded and later removed from the final deliverable DTM file.

Imagery is georeferenced to Massachusetts State Plane Mainland (Lambert Conformal Conic Projection) NAD83 coordinate system, denominated in meters.

Color balancing was performed using METRO_NICE software. The resulting images were mosaicked into one seamless database of imagery and extracted to match the existing MassGIS Orthophoto Index Grid tile layout (each image tile covers 4,000x4,000 meters on the ground.). Images were quality-controlled by Sanborn using Adobe PhotoShop software. Final deliverables included 1/2-meter pixel resolution GeoTiff images with supplementary tfw files and metadata.

MassGIS quality assurance included rigorous independent checks of the spatial accuracy using other datasets of significantly higher accuracy, and field work that included the capture of highly accurate GPS points that were compared to the same locations appearing on the deliverables. MassGIS also assessed the visual quality and appearance of the images.

Distribution

Due to the large size of the original half-meter GeoTIFF images, MassGIS is also making these images available in the compressed MrSID and JPEG 2000 (JP2) formats. Options include images tiled by the orthophoto index as wells as large regional mosaics, which comprise from 26 to 73 ortho index tiles. Users may access the JPG2000 data by free download from the MassGIS ftp server or by ordering the Mosaics and MrSID tiles data on CD or DVD. Details are provided below.

Original vs. "Contrast Stretched" Imagery
MassGIS has produced a set of "Contrast Stretched" MrSID and JP2 data for users who do not have the software tools to modify the appearance of the original imagery. This second set of compressed data was produced from a set of GeoTIFFs that MassGIS modified with a 2.75 standard deviation linear contrast stretch in Erdas Imagine software. A linear contrast stretch is a simple way to improve the visible contrast of an image by changing the individual values of the pixels in the image. Usually, a contrast stretch is performed only on the display device (screen, printer, etc.), so that the data file values do not change. In this case, the stretched pixel values were saved to the tiffs and the tiffs were used to make the second set of MrSID and JP2 files.

MassGIS is making this second set of images available for those whose software does not permit display adjustments, or who simply prefer not to adjust the contrast. These contrast stretched images may help solve some of the problems that some users encountered with getting the original images to look the way they wanted. These new images have a much greater contrast when compared to the originals. The drawback is that the stretch is "fixed", so that you cannot recoup the original pixel values. With the original set of images (GeoTIFF, MrSID, and JP2 formats), the user can achieve the same type of contrast adjustment seen in the second set of imagery and still make use of the full range of data values acquired by the digital cameras.

Here are screen shots that compare the same area in the original MrSIDs (with no stretch or modification) and the contrast stretched imagery. To learn how to adjust the appearance of the original imagery to your liking, see the Display Options page pdf format of    COQ 2005 Display Options    doc format of COQ 2005 Display Options DOC file size 1MB .
 

Free Download
Images in the following formats are available for download as 4 km tiles (based on the Ortho Index tiling scheme)

JPEG 2000, lossy, at 16:1 compression ratio, 4 bands (RGB and IR).15 MB each. Two sets:
From original GeoTIFFs
From contrast stretched GeoTIFFs
}
}