$LastChangedDate: 27-Juil-2011 $

# CL_gm_equatorialOverlap

Ratio between sensor footprint and gap between ground tracks

## Calling Sequence

       [eq_overlap]=CL_gm_equatorialOverlap(alt,inc,view_angle)

## Description

- Computes the ratio Q = Leq/Ded where:

  - Leq: portion of the equator seen by a sensor during the time it crosses the equator.

  - Deq: gap between 2 consecutive ground tracks at equator.

- Notes:

  - The planet is assumed spherical, and the orbit circular.

  - The sensor is conic and oriented towards the descending vertical.

  - The gap between 2 consecutive ground tracks is computed taking the effect of J2 into account.

  - The result is undefined (%nan) if inclination is 0 or %pi.

## Parameters

alt:

  Satellite's altitude [m] (1xN or 1x1)

inc:

  Orbit's inclination [rad](1xN or 1x1)

view_angle:

  Sensor half view angle = angle from the descending vertical [rad] (1xN or 1x1)

eq_overlap:

  ratio (1xN)

## Authors

- CNES - DCT/SB

## Bibliography

- 1) Satellites orbites et missions - Michel Capderou

## See also

- CL_gm_equatorialSwath

## Examples

    alt = [822.e3 630.e3] ;
    inc = [CL_deg2rad(98.72) CL_deg2rad(96.72)];
    view_angle = [CL_deg2rad(50.5) CL_deg2rad(30.5)];
    [eq_overlap] = CL_gm_equatorialOverlap(alt,inc,view_angle);