**Type**- Secondary Section - depends on
`CRV`Flag. **Description**- Specify local Radius of Curvature to replace default value (6367.421km)
**Format**- Single field
Field Type Description Range `RADCRV`R*8 Radius of curvature [km] 2000:100000 **Notes**- For limb-geometry calculations the RFM assumes a locally spherical
atmosphere characterised by the local radius of curvature. Note that
this is
*not*the same as local radius: for example at the poles the radius is a minimum while the radius of curvature is a maximum. The radius of curvature also depends on viewing direction: the radius of curvature viewing north-south at the equator is smaller than viewing east-west. - The radius of curvature is assumed to apply at an absolute profile altitude 0km (which is not necessarily the surface altitude). This is the only component in the RFM where absolute altitude makes any difference.
- Variations in the earth's radius of curvature lead to differences < 1% in calculated values which are negligible for many applications. The main use of this section is when exact agreement is required, or when applying the RFM to different planetary atmospheres.
- The default value is set to be the same as the mean earth radius,
parameter
`REARTH`in`phycon.inc` - The min/max allowed values are just sanity checks, set in
`inpcrv.for`

- For limb-geometry calculations the RFM assumes a locally spherical
atmosphere characterised by the local radius of curvature. Note that
this is
**Example***CRV 6378.164 ! Earth's equatorial radius (for EW view at equator)