Advancing informed visual impact analysis and mitigation

Information for Using the Wind Turbine Visibility and Visual Impact Threshold Distances Database

Instructions and usage limitations for using the Wind Turbine Visibility and Visual Impact Threshold Distances database, which is accessible via the Web or Google Earth KMZ file.

In a study sponsored by the U.S. Department of the Interior Bureau of Land Management's Wyoming State Office, 377 observations of 5 wind facilities in Wyoming and Colorado were made under various lighting and weather conditions in three different seasons. Facility visibility was rated on a numeric scale keyed to written descriptions of apparent contrast levels.

Field data and photographs taken for the study are available for public use in an online database that can be accessed via the Web or through a KMZ file for viewing in Google Earth or similar software. A publication containing an in-depth discussion of the study is also available.

Wind Turbines in Wyoming

Study Procedures Summary

Five wind facilities (listed below) in southeast Wyoming and northeast Colorado were observed and photographed in the course of four field visits in 2011. Some repeat observations were conducted from identical locations. A total of 377 daytime observations were made from 122 study observation points (SOPs).

All observations and visibility ratings were based on views of the facilities in the field, not on the photographs taken during the observations.

Data from all observations are captured on an observation form that records location; date and time; weather; lighting; solar azimuth and elevation; distance and bearing to the facility; and the visibility of blade movement, blade glinting, lighting, and other visual phenomena associated with the facility. Most observations include one or more photographs, with most observations having multiple photographs at a variety of focal lengths.

Accessing the Data and Photographs

The study data and photographs can be accessed through either the online database or the KMZ file (KMZ, 35KB). Both sources contain the same information and photographs, and differ only in that the online database allows querying for multiple records using study variables, whereas the KMZ allows browsing through the Google Earth map-style interface.

The KMZ file itself contains usage instructions specific to using the KMZ; however, KMZ users should also read the following information, most of which applies to both the KMZ and the database.

Accessing Observation Data and Photographs through the Online Database

To access the study's observation data and photographs through the database, select one or more search criteria available on the search form. The search results page will contain all observations that meet the search criteria, along with a number of data fields from the observation, which can be used to sort search results in various ways.

Clicking the links in the "SOP ID" field will retrieve records for all observations that were made from the selected SOP; in cases where observers returned to the same SOP at different times of day or different dates, there will be multiple observations at an SOP.

Clicking the links in the "Details" field will retrieve detailed data for the observation selected, including all fields on the Observation Data Form and links to any photographs taken during the observation.

Click the "View Complete Form" link under Visibility Rating Forms to see the observers' individual visibility ratings and notes on their observations.

Accessing Observation Data and Photographs through the KMZ File

Choose an SOP (the white bullseye icons) from the Google Earth map or from the subfolders under VITD SOP folder on the left side menu (View > Sidebar). The VITD folders on the left side menu are organized by wind facility name; each folder contains the observations for that facility. After selecting an SOP, click it to view the SOP summary form. Click the "View Data from SOP..." link in the SOP summary form to see a list of observations made at that SOP. Click the "Observation Details" link to view detailed observation data and photos.


Choose an observation (the blue bullseye icons) from the Google Earth map or from the left side menu (View > Sidebar) to view an observation summary form, and then click the "Observation Details" link to view detailed observation data and photos.

Orange bullseye icons are wind facility base points. The facility base point is the reference location from which distances to the wind farm from SOPs are measured.

Retrieving Photographs

Links to the photographs are on the Observation Summary and Observation Details page. Most observations have multiple photographs of the facility taken at a variety of focal lengths (see "About the Photographs" below). Low-resolution preview images may be viewed by rolling the mouse cursor over the link. Clicking the "Download" link will download the high-resolution version of the photograph, which should be used for any analytical purposes. Users may need to zoom in on images to see them at full resolution.

Calculating the Correct Photograph Viewing Distance

If the photographs are used for visual impact assessments or related analytical purposes, viewing them from the correct viewing distance is important. However, determining the correct viewing distance requires users to have three measures in hand: the focal length used for the photograph, the camera image sensor width, and the intended or actual display width used to view the image. A photograph viewing distance calculator utility has been integrated into the database, simplifying the calculation of viewing distance. Users need to specify only the output display width. The integrated software will calculate and display the correct viewing distance for the photograph.

Clicking the "Calculate" link will display a dialogue box. Enter the desired display width (e.g., your monitor display width) into the text entry box, then click "calculate." The correct viewing distance will be displayed.


Twenty nine of the observation records include associated panoramic images that afford a much wider-angle view of the facility and its environs. If an observation includes a panorama, it will be described and a link will be provided after the listing of photographs for the observation. The panoramas consist of conventional 50 mm focal length photographs (35 mm equivalent focal length) that have been stitched together digitally to create very wide-angle views. Please note that the panoramic images have not been spatially corrected and contain distortions, which may be substantial in some cases. The panoramic images are available as high-resolution JPEGs or as interactive Flash-based files. The free Adobe Flash Player is required to view the interactive panoramas.

About the Photographs

The majority of study photographs in the database were taken with a GPS-enabled Nikon D7000 digital SLR camera, using a Nikkor 18–105 mm digital zoom lens (35 mm equivalent focal length of approximately 27–157 mm). Image sensor width was 26.3 mm. A small number of photos in the database were taken with a GPS-enabled Ricoh Caplio 500SE, with a built-in zoom lens (35 mm equivalent focal length of approximately 28–85 mm). No filters were used for the photography. Photographs are high-resolution JPEG files that were compressed at the time the photograph was taken. No cropping, image enhancement, or other post-processing was used on the images. Nearly all of the photographs have useful EXIF header data that can be accessed with Adobe Photoshop and a variety of other software programs, or simply by using the "information" feature of the Windows desktop.

Many of the photographs were taken in very windy conditions. This circumstance resulted in windblown dust and camera shake, despite the use of a tripod; image quality suffered as a result.

Observed Wind Facilities

The following wind facilities were observed in the study:

The primary wind energy facilities analyzed in this study included the following:

  • Cedar Creek I Wind Farm: Cedar Creek I Wind Farm (hereafter referred to as "Cedar Creek") is owned and operated by Babcock & Brown/BP America and is located on Pine Bluff in far northeastern Colorado, about 10.3 km (6.4 mi) east of Grover, Colorado, and about 24 km (15 mi) south of Pine Bluffs, Wyoming. The total generating capacity for Cedar Creek is 300.5 MW.
    The Cedar Creek I wind energy facility consists of 274 wind turbines, 53 of which were General Electric 1.5-MW Model SLE wind turbines with hub heights of 77 m (253 ft) and blade tip heights of 119 m (390 ft), and 221 were Mitsubishi 1.0-MW Model MWT1000a wind turbines with hub heights of 61.4 m (201.4 ft) and blade tip heights of 90.7 m (297.6 ft).
  • Seven Mile Hill Wind Farms: The Seven Mile Hill Wind Farms (hereafter referred to as "Seven Mile") are located in Carbon County, Wyoming, between Hanna and Medicine Bow. The wind energy facilities consist of 79 General Electric 1.5-MW Model SLE turbines, which were installed in two phases (66 in the Seven Mile Hill I phase and 13 in the Seven Mile Hill II phase).
    These turbines have rotor diameters of 77 m (252 ft) and tower hub heights of 80 m (262 ft). The blade tip heights are approximately 117.0 m (383 ft) for a typical turbine of this model (GE, 2011). The wind energy facility has a generating capacity of 99 MW for the first phase and 19.5 MW for the second. For this study, the installations are treated as one wind energy facility.
  • Dunlap Ranch Wind Energy Project: The Dunlap Ranch Wind Energy Project (hereafter referred to as "Dunlap") is located in Carbon County, Wyoming, near Medicine Bow. The first phase of this wind energy facility consists of 74 General Electric 1.5-MW Model SLE turbines, with a generating capacity of 111 MW. These models consist of structures with tower hub heights of 80 m (262 ft) and rotor diameters of 77 m (253 ft). The blade tip heights are approximately 117.0 m (383 ft) for a typical turbine of this model.

Two additional facilities, the Happy Jack and Silver Sage Wind Farms, were included in the January 2011 fieldwork for the maximum visibility distance assessment. These wind farms are located in Laramie County, west of Cheyenne, Wyoming.

The combined wind farms occupy an irregular polygon measuring roughly 4.5 km (2.8 mi) east-west and 2.9 km (1.8 mi) north-south. The 34 wind turbines (14 at Happy Jack and 20 at Silver Sage) are Suzlon 2.1-MW Model S88/2100 wind turbines, with hub heights of 88 m (289 ft) and blade tip heights of 123 m (404 ft).

Usage Limitations and Restrictions

The photographs in the database were taken for scientific purposes, not for aesthetic purposes. The database is not intended to provide a repository of high-quality photographs of wind facilities.

Because of limitations of the equipment and methods used, the photographs may underrepresent the contrasts observed in the field.

All photos and data are provided as is. The data are provided for the convenience of users and may contain errors and omissions.

These images are provided for free and unrestricted public use. Please credit Argonne National Laboratory as the source if any photos or data are used.

For More Information

To learn more about EVS visual resource analysis projects, contact: