Wall Street analysts have used satellite imagery of Wal-Marts to help them estimate the company's sales, according to a report on CNBC.

The analysts concluded that there was enough correlation between activity in the satellite pictures of Wal-Mart’s parking lots and the chain’s quarterly earnings that they included the data in a UBS company report on Wal-Mart.

UBS purchased the analysis from a small two-year old Chicago-based firm called Remote Sensing Metrics LLC, which had scoured satellite images of more than 100 Wal-Mart stores taken by companies such as DigitalGlobe and GeoEye.

By counting the cars in Wal-Mart’s parking lots month in and month out, Remote Sensing Metrics staff were able to build a formula to predict the company’s quarterly revenue month.

UBS expects to begin adding satellite analysis into its Wal-Mart reports on a regular basis.

Some analysts have also used satellite pictures of big ports to estimate economic activity, and mapping firm Lanworth uses satellite images to predict the prices of corn and wheat by using infrared and microwave images of the entire planet taken twice a day, according to the CNBC report.