Astro GIS

Global Site Selection for Astronomy 

Summary (quoted from Aksaker 2020)

The site selection procedure is complex due to its nature: Data from different sources are combined and analyzed together. Tools and techniques of Geographic Information System (GIS) have already provided many solutions to these kinds of problems it offers cost and time-efficient solutions to decision makers. Therefore, GIS techniques in site selection are widely used in many fields: hospitals, solar and wind farmsteads, urban solid waste plants, as well as observatories 

A global site selection for astronomy was performed with 1 km spatial resolution (∼ 1 Giga pixel in size) using long-term and up-to-date datasets to classify the entire terrestrial surface on the Earth. Satellite instruments are used to get the following datasets of Geographical Information System (GIS) layers: Cloud Coverage, Digital Elevation Model, Artificial Light, Precipitable Water Vapor, Aerosol Optical Depth, Wind Speed, and Land Use – Land Cover. A Multi Criteria Decision Analysis (MCDA) technique is applied to these datasets creating four different series where each layer will have a specific weight. We introduce for the first time a “Suitability Index for Astronomical Sites” namely, SIAS. This index can be used to find suitable locations and to compare different sites or observatories.

Mid-western Andes in South America and the Tibetan Plateau in west China were found to be the best in all SIAS Series. Considering all the series, less than 3 % of all terrestrial surfaces are found to be the best regions to establish an astronomical observatory. In addition to this, only approximately 10 % of all current observatories are located in good locations in all SIAS series.

Amateurs, institutions, or countries aiming to construct an observatory could create a short-list of potential site locations using the layout of SIAS values for each country without spending time and budget. 


Some datasets use more than one product. The resolution given here represents the original dataset; the final resolution is fixed at 1 km. Time coverage is usually taken from the satellite repositories. Two products of Aqua/Terra satellites have different time coverage: Feb 2000 to date and 2002 to date for MOD and MYD products, respectively. Time coverage of CC was started in July 2003 due to irregularities in earlier records from the MYD35 L2 product. 

Geotif and kmz can be viewed with offline free software like Qgis, and Google Earth. Online map providers like Google Earth Online or similar platforms can be used for viewing the files.


We have collected all datasets from different missions and instruments on board of satellites we have studied. Links, websites, resources or repositories of dataset we downloaded are listed in the table given above. Downloading the layers are automated using an in-house coded python script.