When ordering archive imagery, users will want to know more about the imagery and its details before placing an order. This is to ensure they are getting the resolution they expect, no clouds or haze are present, and the archive image covers 100% of their area of interest.
In this support article, we provide tips for searching and ordering archive imagery.
Check the Preview
We do have a full support article on the preview image tool, but we will summarize it here as well.
The preview tool on EXPLORE provides users the ability to view a downsampled version of the archive image. The resolution will not reflect the true resolution of the image. Due to restrictions, we cannot show the full resolution as a preview, but users can view samples of the imagery in our Product Library, or through our support article here.
To open a preview, a user must click on the returned archive result located in the left side column on the main page.
The preview helps users check if clouds or haze are present within their area of interest (AOI) and whether it covers the entire area.
Note: Users can also view the preview in the cart. A "Preview" button will appear for each archive image added to the cart.
Cloud Cover
The cloud cover percentage of the entire image capture footprint can be found in the (i) section located on each returned archive search result.
It is always recommended to view the cloud cover information as very small clouds or thin haze may not always be visible.
Off-Nadir Angle
The off-nadir angle represents the angle between the vertical line of sight and the actual line of sight between the satellite and an object.
Diagram explaining how the off-nadir angle varies depending on the actual line of sight the satellite has of an object. Credit: European Space Imaging.
The off-nadir angle can have a profound impact on the resolution of an image. All suppliers recommend to acquire a best true resolution, users will desire archive images with off-nadir angles between 0 and 30 degrees. Once you begin to increase above 30, the quality and resolution of the archive image will begin to degrade. >30 degree off-nadir is beneficial for acquiring oblique images of the surface (you can see more building heights and details), but not ideal for viewing the full resolution of an image.