Solar Clock Object - Metasys - LIT-1201793 - Software Application - Site Management Portal - 12.0.50

Metasys Site Management Portal Help

Product name
Site Management Portal
Document type
User Guide
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Menu Selection: Insert > Object > Solar Clock

The solar clock object computes Present Value (Night/Day), Sun Position (Azimuth and Elevation), and Sunrise and Sunset times based on the local position (Latitude and Longitude) and local time and time zone information. This information is needed to control external motorized louvers as part of bioclimatic facades for buildings and may also be used to position tracking photovoltaic solar arrays. The Sunrise/Sunset times can be used for external lighting control.

This object runs on a periodic basis to compute its attributes. The equations to compute azimuth, elevation, sunrise, and sunset attributes were obtained from the National Oceanic and Atmospheric Administration (NOAA) Web site ( The object obtains the Local Time, UTC Offset, DST Status, and DST Offset from the BACnet Device object.

Latitude and Longitude for this object are provided in decimal degrees. Often, these values are provided as degrees, minutes, and seconds. There are numerous Web sites that can convert the latitude and longitude values, if necessary. In addition, you can obtain your current location on the planet from free tools such as Google Earth. Google Earth includes an option to provide your location in decimal degrees.

Note: For correct sunrise and sunset calculations, you must apply north/south and east/west rules. North latitudes are preceded by a plus, South latitudes are preceded by a minus. West Longitudes are preceded by a minus, East Longitudes are preceded by a plus. See Table 1.
Table 1. Latitude and Longitude Examples
Location Landmark Latitude Longitude
Milwaukee, WI, USA Brengel Technology Center 43.037507 -87.904456
Paris, France Notre Dame Cathedral 48.854212 2.347641
Cape Town, South Africa Green Point Stadium -34.903488 18.411073
Sydney, Australia Opera House -33.857184 151.215176
Beijing, China Tiananmen Square 39.06514 116.391213

For general information on Metasys system objects, see Common Object Attributes.