# Level 2A

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This is a precision preprocessing level which includes the radiometric corrections performed in level 1A and bidirectional geometric corrections without the use of ground control points.

### Corrections

The scene is rectified according to a given cartographic projection (conformal Lambert, UTM, oblique equatorial, polar stereographic, polyconic, etc.). The image is also rotated and aligned with true north.

Corrections are performed using only satellite attitude data (variations in the satellite attitude during imaging) and imaging geometry without using ground control points (topographic maps are not therefore required).
These corrections and the consideration of a reference elevation chosen by the customer make level 2A more accurate than level 1B.

### Accuracy

Although the image's internal accuracy is better (0.0005) compared to level 1B, absolute location accuracy is unchanged (approximately 500m). It can, however, be accurately adjusted by X and Y translation with respect to a known point.

### Image size

Resampling increases both the number of pixels per line and the number of lines, in proportions that vary according to viewing angle and image orientation angle. The rectangular shape of the image is restored by adding border pixels.
Level 2A products can be supplied as full scenes or as quarter scenes

### File Size

In panchromatic (P) mode, the number of pixels per line is between 6000 and 10200 (depending of viewing angle and image orientation angle).
Since a pixel is coded over 1 byte, the total volume of a digital product can vary between 36 Mbytes and 100 Mbytes (not including border pixels and auxiliary data files).

Inmultispectral (XS)mode, and for each spectral band, the number of pixels per line and the number of lines can vary between 3000 and 5100.
Since each pixel is coded over 3 bytes (XS mode) the total volume of a digital product can vary between 36 Mbytes and 100 Mbytes (not including border pixels and auxiliary data files).

### Use

This is the level used when a standard cartographic projection without a high location accuracy is required.

### Medium and format

Level 2A products are distributed in SPOT Standard digital product format.

Range
CCT (full scene only) | P and XS
CD-Rom (full scene only) | P and XS
Film | P and XS
Paper print | P and XS