About the 2003-2004 RIDOT orthophotography product:

 

This product was released by the Rhode Island Geographic Information System (RIGIS) in November of 2005.

 

Digital orthophoto images on this web site were originally produced by Chas. H. Sells under contract to the Rhode Island Department of Transportation (RIDOT). The images were obtained in April 2003 for eastern Rhode Island (and Block Island) and April 2004 for western portions of the state. The above map shows the division of the state by the year the photography was acquired.  Although this graphic indicates a defined image line of images for each of the individual years, the orthophotos along the seam may include some ambiguity or mixing of information from each year due to the nature of the digital image production process.  The Adobe Acrobat file photcenter0304.pdf locates the photocenters and notes the years of the original images.

 

Following acceptance of the product by RIDOT, the images were packaged on CDROM media by the RIGIS Coordinator at the Rhode Island Department of Administration. The Department of Administration as a participant in the RIGIS has provided copies of the compressed images for inclusion in the RIGIS database.

 

The conventional aerial photography was scanned, and automated into orthographically corrected digital images. Original images as provided by the consultant were in a Tagged Image File format (TIF) with a pixel size of 2 square feet and georegistered to the Rhode Island state plane coordinate system in U.S. survey feet. The entire data set of TIF images for Rhode island totaled 410 individual image tiles 10,000 feet on a side and approximately 73.25 megabytes in size.

 

The original TIF images were mosaiced to 4 image per square configuration and compressed using MrSID GeoExpress 5.0 software into a Lizardtech MG3 file format at a compression ratio of 25:1.  In choosing this compression ratio consideration was given to preserve the highest possible image resolution while still fitting all the photos on three CD products for the total package of images. Each mosaiced image was given a file name consisting of the first two numbers of the Rhode Island state plane easting coordinate followed the by the first two numbers of the Rhode Island state plane northing coordinate of the upper left hand corner of the mosaiced image tile. In instances on the periphery of the grid of images for the state where 4 square mosaics were not possible, a naming convention consisting of a similar numeric sequence followed by a V(vertical) or  H (horizontal) for orientation followed by a single digit for the number of TIF images used the resulting MrSid mosaic.

 

Images as originally provided were from 1:30,000 flight photo scale and reduced to 1:5,000 image scale following the scanning and orthorectification process. Map accuracy for 1:5,000 scale is plus or minus 3-5 meters. Since part of the facility to users with computer software is an ability to zoom in or blow up these images and compare them with other data, these accuracy and resolution criteria must be kept in mind while using this product.

 

As packaged on CD-ROM media by RIGIS, there are three CDs containing the RIGIS03/04 image data set with some overlap to capture entire town areas on one CD. There are 41 year 2003 images on RIGIS03east; 40 year 2004 images and 5 overlapping 2003 images on RIGIS04South; and 36 year 2004 images and 14 overlapping 2003 images on RIGIS04North.

 

Each compressed mosaiced image in MrSID MG3 format is about 11.75 megabytes in size. These images can be exported back to TIF format using MrSID software tools available from Lizardtech.com. When reverted back to full TIF images, a corresponding 4 square mosaic size is about 300 megabytes.

 

Original Metadata records as provided by the Chas H. Sells Inc. and as modified by the RIGIS are contained in a file named rigis0304.html.

 

Software

Those who are not already GIS users or who lack the specialized software required for extended GIS analysis, we have included Lizardtech's Express View plugin in the Software file folder of this CD. You will need to install the MrSID ExpressView 4.0 plugin software on your computer before viewing the images.  The MrSID plugin is a very small installation and runs under Internet Explorer or Netscape web browsers on computers running the Microsoft Windows operating systems. The ExpressView plugin program is also available for free download over the world wide web and can be accessed at http://www.lizardtech.com/. Additional software and tools for using MrSid MG3.0 files may be found on this same site.

 

An image index shapefile is available. This shapefile is in NAD83 RI-State Plane Feet in keeping with the standard mapping coordinate system for digital map data in the RIGIS database. No metadata are available for this shapefile.

 

If you have Arcview3.X you will have to download and install the AVMrSid.dll file from ESRI.  If you are using ArcGIS8.3 with ArcMAp you will have to download and install the ArcGIS Raster Update patch that supports the MrSID MG3 image format.  ArcGIS 9.X can view these files directly.

 

For information about other GIS and image processing software with which to view MrSID images, please see http://www.lizardtech.com/.

 

About RIGIS

The Rhode Island Geographic Information System (RIGIS) is a consortium of government and private organizations employing computer and communications technology to manage and use a collective database of comprehensive geographically related information. The mission of the RIGIS is to monitor, coordinate, and provide leadership for activities related to the use of GIS technology within Rhode Island, to support initiatives to implement or use the technology, and to manage and provide access to a common database of geographically referenced information.

The RIGIS database is maintained on a server at the University of Rhode Island's Kingston Campus, and at the Rhode Island Department of Administration in Providence. The Environmental Data Center within the Department of Natural Resource Sciences at the University provides on line access (web-browser only) to most RIGIS data via the Internet at www.edc.uri.edu/RIGIS. Data can also be provided on optical media by request from the RIGIS coordinator at the RI Department of Administration's Division of Information Technology at rigis@admin.ri.gov.

 

RIGIS data, including those data included on this web site, are copyright protected and licensed for use by the RI Board of Governors for Higher Education. Restrictions include prohibiting the secondary distribution of RIGIS data without prior written approval.

 

RIGIS Contact Information:

John Stachelhaus-RIGIS Coordinator
RI Dept. of Administration/DoIT
1 Capitol Hill
Providence, RI 02908

email: rigis@admin.ri.gov

telephone: (401) 222-6483