@geodetic-lse/geodesy

Geodesy tools for least squares adjustment of surveying networks. Currently supports levelling networks (1D height adjustment).

Built on top of @geodetic-lse/core.

Installation

npm install @geodetic-lse/geodesy

Quick start

import { loadLevellingNetwork, adjustLevellingNetwork } from '@geodetic-lse/geodesy'

const input = {
    network: {
        name: 'My levelling network',
        points: [
            { id: 'A', height: 100.0, is_fixed: true },
            { id: 'B', height: 0, is_fixed: false },
            { id: 'C', height: 0, is_fixed: false },
        ],
        observations: [
            { station: 'A', target: 'B', type: 'delta_height', value: 5.123, sigma: 1.0 },
            { station: 'B', target: 'C', type: 'delta_height', value: 3.456, sigma: 1.0 },
            { station: 'A', target: 'C', type: 'delta_height', value: 8.58, sigma: 1.0 },
        ],
        parameters: {
            type_computation: 'constrained',
            sigma_0: 1.0,
        },
    },
}

const network = loadLevellingNetwork(input)
const result = adjustLevellingNetwork(network)

console.log('Redundancy:', result.redundancy)
console.log('s0 (a posteriori):', result.s0.toFixed(4))
console.table(result.adjustedPoints)
console.table(result.residuals)

Input format

The input is a JSON object with a network key:

{
    "network": {
        "name": "Network name",
        "source": "Data source",
        "description": "Description",
        "crsVertical": "IGN69",
        "points": [...],
        "observations": [...],
        "parameters": {...}
    }
}

Points

| Field | Type | Required | Description | | ---------- | --------- | -------- | ------------------------------------------------------------------- | | id | string | yes | Unique point identifier | | height | number | yes | Height in metres (initial approximation for unknowns) | | is_fixed | boolean | yes | Whether the point is held fixed | | sigma | number | no | Precision in mm — required for fixed points in free-adjusted mode |

Observations

Only delta_height observations are currently supported.

| Field | Type | Required | Description | | --------- | -------- | -------- | ------------------------------------ | | station | string | yes | Origin point ID | | target | string | yes | Target point ID | | type | string | yes | Must be "delta_height" | | value | number | yes | Observed height difference in metres | | sigma | number | yes | Observation precision in mm |

Parameters

| Field | Type | Default | Description | | ------------------ | -------- | --------------- | ------------------------------------------------------------- | | sigma_0 | number | 1.0 | A priori reference standard deviation | | type_computation | string | "constrained" | Adjustment mode — see Computation modes |

Computation modes

| Mode | Description | | --------------- | ------------------------------------------------------------------------------------- | | constrained | Fixed points define a rigid reference frame (default) | | free | One fixed point defines the datum; others are adjusted freely | | free-adjusted | Fixed point heights are used as weighted pseudo-observations; all points are unknowns |

In free-adjusted mode, each fixed point must have a sigma value defined.

API

loadLevellingNetwork(input)

Parses and validates a raw input object. Throws descriptive errors on invalid data.

Returns a NetWork object ready for adjustment.

adjustLevellingNetwork(network)

Performs the least squares adjustment.

Returns a LevellingAdjustmentResult:

| Field | Type | Description | | ---------------- | ----------------------- | ---------------------------------------------------- | | adjustedPoints | AdjustedPoint[] | Adjusted heights with corrections and sigmas | | residuals | ObservationResidual[] | Residuals and reliability indicators per observation | | s0 | number | A posteriori standard deviation | | sigma0 | number | A priori standard deviation | | redundancy | number | Degrees of freedom | | Kll | Matrix | Variance-covariance matrix of observations | | Qll | Matrix | Weight coefficient matrix |

AdjustedPoint

| Field | Type | Description | | ------------ | --------- | -------------------------------- | | id | string | Point identifier | | height | number | Adjusted height [m] | | correction | number | Applied correction [m] | | sigma | number | Standard deviation [mm] | | is_fixed | boolean | Whether the point was held fixed |

ObservationResidual

| Field | Type | Description | | ---------- | -------- | ---------------------------------------------------- | | station | string | Origin point | | target | string | Target point | | observed | number | Observed height difference [m] | | computed | number | Computed height difference from adjusted heights [m] | | residual | number | Residual v [mm] | | sigma | number | Standard deviation of residual [mm] | | wi | number | Normalized residual — Baarda's test statistic | | zi | number | Local redundancy number [%] | | gi | number | Estimated gross error [mm] |

License

MPL-2.0