```
pub trait EstimateFrom<O: State, M: Measurement>where
Self: State,
DefaultAllocator: Allocator<<O as State>::Size> + Allocator<<O as State>::VecLength> + Allocator<<O as State>::Size, <O as State>::Size> + Allocator<Self::Size> + Allocator<Self::VecLength> + Allocator<Self::Size, Self::Size>,{
// Required methods
fn extract(from: O) -> Self;
fn sensitivity(
msr: &M,
receiver: Self,
transmitter: Orbit,
) -> OMatrix<f64, M::MeasurementSize, Self::Size>
where DefaultAllocator: Allocator<M::MeasurementSize, Self::Size>;
}
```

## Expand description

The Estimate trait defines the interface that is the opposite of a `SolveFor`

.
For example, `impl EstimateFrom<Spacecraft> for Orbit`

means that the `Orbit`

can be estimated (i.e. “solved for”) from a `Spacecraft`

.

In the future, there will be a way to estimate ground station biases, for example. This will need a new State that includes both the Spacecraft and
the ground station bias information. Then, the `impl EstimateFrom<SpacecraftAndBias> for OrbitAndBias`

will be added, where `OrbitAndBias`

is the
new State that includes the orbit and the bias of one ground station.

## Required Methods§

source#### fn sensitivity(
msr: &M,
receiver: Self,
transmitter: Orbit,
) -> OMatrix<f64, M::MeasurementSize, Self::Size>

#### fn sensitivity( msr: &M, receiver: Self, transmitter: Orbit, ) -> OMatrix<f64, M::MeasurementSize, Self::Size>

Returns the measurement sensitivity (often referred to as H tilde).

##### §Limitations

The transmitter is necessarily an Orbit. This implies that any non-orbit parameter in the estimation vector must be a zero-bias estimator, i.e. it must be assumed that the parameter should be zero.
This is a limitation of the current implementation. It could be fixed by specifying another State like trait in the EstimateFrom trait, significantly adding complexity with little practical use.
To solve for non zero bias parameters, one ought to be able to estimate the *delta* of that parameter and want that delta to return to zero, thereby becoming a zero-bias estimator.

## Object Safety§

**not**object safe.

## Implementors§

### impl EstimateFrom<Spacecraft, RangeDoppler> for Spacecraft

### impl<O> EstimateFrom<O, O> for O

A generic implementation of EstimateFrom for any State that is also a Measurement, e.g. if there is a direct observation of the full state.
WARNING: The frame of the full state measurement is *not* checked to match that of `Self`

or of the filtering frame.