Correction & Verification User Guide¶

curryer.correction answers two practical questions about a mission’s geolocation. Each is driven by one configuration file and a short, copy-paste call — there are no Python classes to write.

Verification — “Does our current geolocation meet the accuracy requirement?” Returns a pass/fail verdict with per-point error.
Correction — “What adjustment makes it more accurate?” Tries a range of pointing/timing adjustments and reports the best one.

Correction is verification run in a loop: for each candidate adjustment it re-geolocates the observations, then evaluates the result with verification.

correction loop
│
├── [per candidate adjustment]
│   ├── generate trial SPICE kernels
│   ├── geolocate observations (SPICE → lat/lon/alt)
│   └── verification ──► GCP pairing
│                    ──► image matching
│                    ──► error statistics
│                    ──► pass/fail verdict
│
└── aggregate results → best adjustment + verdict

Quickstart¶

Both workflows read the same mission config file. Copy examples/correction/example_config.json, edit the values for your mission, and run.

Check accuracy — verification:

from curryer.correction import load_setup_from_json, verify

setup = load_setup_from_json("mission.json")
result = verify(setup, image_matching_results=[...])   # one dataset per GCP comparison

print(result.summary_table)        # per-point pass/fail table
print("Passed:", result.passed)

Find a correction — correction loop:

from curryer.correction import load_config_files, run_correction, CorrectionInput

setup, sweep, output = load_config_files("mission.json")
inputs = [CorrectionInput(telemetry_file="obs.nc", science_file="obs.nc", gcp_file="chip.nc")]

result = run_correction(setup, sweep, inputs, work_dir="out", output=output)

print(result.summary_table)
print(result.recommendation)

The data you process (observation and GCP files) is passed at run time via inputs=, not stored in the config file — it’s this-run data, not a property of the mission.

How a mission is configured¶

Everything a mission needs lives in one JSON file with up to three sections. You edit values — you don’t write code.

Section	Answers	How often it changes
`setup`	Where are the kernels? Which instrument? What’s the accuracy spec?	Once per mission
`sweep`	Which adjustments to try, and how to search them?	Per experiment
`output`	What to name the result file (optional)	Rarely

{
  "setup": {
    "geo": {
      "meta_kernel_file": "path/to/mission.kernels.tm.json",
      "generic_kernel_dir": "data/generic",
      "instrument_name": "YOUR_INSTRUMENT",
      "time_field": "corrected_timestamp"
    },
    "requirements": {
      "performance_threshold_m": 250.0,
      "performance_spec_percent": 39.0
    }
  },
  "sweep": {
    "search_strategy": "random",
    "n_iterations": 50,
    "seed": 42,
    "parameters": [
      {
        "ptype": "CONSTANT_KERNEL",
        "config_file": "path/to/frame_a.attitude.ck.json",
        "spec": {
          "current_value": [0.0, 0.0, 0.0],
          "bounds": [-300.0, 300.0],
          "sigma": 50.0,
          "units": "arcseconds"
        }
      }
    ]
  }
}

Templates to copy: examples/correction/example_config.json (annotated, minimal) or examples/correction/clarreo_config.json (a complete real mission). Every field is specified in Configuration Reference.

Reuse the setup, try many adjustments¶

The setup is fixed for a mission; the sweep is the cheap, swappable part. Keep one mission.json and either point at per-experiment sweep files (load_setup_from_json + load_sweep_from_json read the setup and sweep sections independently) or adjust in code:

grid  = sweep.with_strategy("grid", grid_points_per_param=5)         # deterministic grid search
wider = sweep.update_param("hps.az_ang_nonlin", bounds=[-100, 100])  # widen one parameter
run_correction(setup, wider, inputs, work_dir="out")

Both return validated copies, so a typo or out-of-bounds value is caught immediately. The update_param selector is the parameter’s position, its spec.field name, or its config_file filename stem.

What to provide for a new mission¶

Copy examples/correction/clarreo_config.json and fill in these values. The JSON path (in parentheses) is where each one goes.

SPICE kernels (setup.geo.meta_kernel_file, generic_kernel_dir, dynamic_kernels) — your mission’s kernel files. dynamic_kernels are regenerated from telemetry on each run.
Instrument (setup.geo.instrument_name) — the NAIF instrument name from your Instrument Kernel, e.g. "CPRS_HYSICS".
Timestamps (setup.geo.time_field) — the column holding uGPS times. If your times need scaling (e.g. GPS seconds → uGPS), set setup.data_config.time_scale_factor to 1e6.
Accuracy requirement (setup.requirements.performance_threshold_m and performance_spec_percent) — the per-point error limit in metres, and the minimum percentage of points that must fall within it.
Adjustments to try (sweep.parameters, correction only) — one entry per pointing offset or timing correction (see Configuration Reference).
Calibration (setup.calibration.los_vectors_file / psf_file) — needed for the built-in image matcher (interim; will become SPICE-derived).

That’s the full setup. The sections below are field-by-field reference and runnable examples.

Verification¶

Verification scores geolocation results against the mission requirement. The recommended input is image_matching_results — a list of xr.Dataset objects (one per GCP comparison) from your image-matching pipeline; this is the path weekly automated checks use.

import xarray as xr
from curryer.correction import load_setup_from_json, verify

setup = load_setup_from_json("mission.json")
results = [xr.open_dataset("matching_result_001.nc")]   # one per GCP comparison

result = verify(setup, image_matching_results=results)  # no SPICE kernels needed for this path

print(result.summary_table)                 # per-point pass/fail table
print("Passed:", result.passed)
print(f"Within threshold: {result.percent_within_threshold:.1f}%")

Input modes¶

verify() takes setup first; everything else is keyword-only (the first input you supply, in the order below, wins):

Mode	Argument	Notes
Pre-computed image matching	`image_matching_results=`	Recommended for production and automated checks
Run image matching on demand	`geolocated_data=`	Custom `setup.image_matching_func`, or built-in pairing+matching with `gcp_directory=`/`los_file=`/`psf_file=`
Explicit file-path pairs	`gcp_pairs=` (+ `los_file=`/`psf_file=`)	Supported
Auto-paired paths	`observation_paths=` + `gcp_directory=`	Supported (+ `los_file=`/`psf_file=`)

The geolocated_data path matches in one of two ways. If you attach a callable to setup.image_matching_func, verify() calls it. Otherwise, supply gcp_directory=, los_file=, and psf_file= and verify() runs built-in spatial pairing + image matching. If neither the override nor that trio is provided, the call raises ValueError.

A runnable example using real test data: examples/correction/example_verification.py

Correction¶

run_correction() is the entry point. It returns the best parameters, a pass/fail verdict, a recommendation, and a summary table.

import pathlib
from curryer.correction import (
    CorrectionInput, load_config_files, run_correction,
)

# Load setup + sweep (+ output) from one JSON file (recommended for production)
setup, sweep, output = load_config_files("examples/correction/clarreo_config.json")

# Each CorrectionInput maps one telemetry + science + GCP triplet.
# Raw (str, str, str) tuples are also accepted.
# S3 URIs ("s3://...") are accepted when boto3 is installed.
inputs = [
    CorrectionInput(
        telemetry_file=pathlib.Path("data/obs_20240317.nc"),
        science_file=pathlib.Path("data/obs_20240317.nc"),
        gcp_file=pathlib.Path("data/gcp/landsat_chip_001.nc"),
    )
]

work_dir = pathlib.Path("workdir_correction")
# NOTE: inputs come before work_dir; output is optional.
result = run_correction(setup, sweep, inputs, work_dir, output=output)

print(result.summary_table)
print("Passed:", result.passed)
print(result.recommendation)

best = min(result.results, key=lambda r: r["rms_error_m"])
print(f"Best RMS: {best['rms_error_m']:.2f} m  (parameters: {best['parameters']})")

(To reuse one setup across many sweeps, see Reuse the setup, try many adjustments above.)

Low-level alternative: `loop()`¶

loop() returns the raw (results, netcdf_data) tuple and only accepts plain (str, str, str) tuples (not CorrectionInput). Note its argument order: work_dir comes before the inputs list.

from curryer.correction import loop

inputs = [("data/obs.nc", "data/obs.nc", "data/gcp.nc")]
results, netcdf_data = loop(setup, sweep, work_dir, inputs)

A workflow template: examples/correction/example_run_correction.py

Loading config from JSON¶

from curryer.correction import load_config_files
setup, sweep, output = load_config_files("mission.json")

load_config_files() reads the setup, sweep, and optional output sections. A missing setup or sweep raises a clear KeyError; output defaults to empty. Load a single section with load_setup_from_json() or load_sweep_from_json().

A complete file, including the spacecraft variable names and output section the Quickstart template leaves out:

{
  "setup": {
    "geo": {
      "meta_kernel_file": "path/to/mission.kernels.tm.json",
      "generic_kernel_dir": "data/generic",
      "instrument_name": "YOUR_INSTRUMENT",
      "time_field": "corrected_timestamp",
      "dynamic_kernels": []
    },
    "requirements": {
      "performance_threshold_m": 250.0,
      "performance_spec_percent": 39.0
    },
    "spacecraft_position_name": "sc_position",
    "boresight_name": "boresight",
    "transformation_matrix_name": "t_inst2ref"
  },
  "sweep": {
    "search_strategy": "random",
    "n_iterations": 50,
    "seed": 42,
    "parameters": [
      {
        "ptype": "CONSTANT_KERNEL",
        "config_file": "path/to/frame_a.attitude.ck.json",
        "spec": {
          "current_value": [0.0, 0.0, 0.0],
          "bounds": [-300.0, 300.0],
          "sigma": 50.0,
          "units": "arcseconds"
        }
      }
    ]
  },
  "output": {
    "output_filename": "correction_results.nc"
  }
}

A frame rotation is authored as a single CONSTANT_KERNEL parameter whose spec.current_value is the [roll, pitch, yaw] triplet.

A fully populated mission example: examples/correction/clarreo_config.json A generic annotated template: examples/correction/example_config.json

Configuration Reference¶

Setup — `setup`¶

The durable, mission-specific configuration (built once, reused across sweeps).

Field	Type	Notes
`geo`	`GeolocationConfig`	Required. SPICE kernel paths and instrument identity
`requirements`	`RequirementsConfig`	Required. Pass/fail thresholds
`data_config`	`DataConfig \| None`	File-loading specification; `None` uses CSV defaults
`calibration`	`CalibrationFiles \| None`	Optional direct LOS/PSF calibration file paths (interim)
`spacecraft_position_name`	`str`	Variable name in the image-matching `xr.Dataset` for SC position
`boresight_name`	`str`	Variable name in the image-matching `xr.Dataset` for boresight
`transformation_matrix_name`	`str`	Variable name in the image-matching `xr.Dataset` for rotation matrix
`image_matching_func`	`Callable \| None`	Optional custom image-matching callable; excluded from JSON

Sweep — `sweep`¶

The parameter-variation experiment, varied between runs. Use sweep.with_strategy(strategy, **changes) and sweep.update_param(selector, **spec_changes) for cheap, re-validated copies.

Field	Type	Notes
`parameters`	`list[ParameterConfig]`	Required (at least one). Parameters to vary
`search_strategy`	`SearchStrategy`	`RANDOM` / `GRID_SEARCH` / `SINGLE_OFFSET`
`n_iterations`	`int`	Iterations (RANDOM / values-per-param SINGLE)
`seed`	`int \| None`	Random seed for reproducible `RANDOM` sweeps
`grid_points_per_param`	`int`	Points per parameter when `GRID_SEARCH` is used
`max_grid_sets`	`int`	Safety cap on total grid-search parameter sets

Output — `output`¶

Field	Type	Notes
`netcdf`	`NetCDFConfig \| None`	NetCDF metadata; `None` auto-populated from the threshold
`output_filename`	`str \| None`	Output NetCDF filename; `None` uses the default

Requirements — `setup.requirements`¶

Field	Type	Notes
`performance_threshold_m`	`float`	Required. Per-measurement nadir-error limit in metres
`performance_spec_percent`	`float`	Required. Minimum % of measurements that must pass

Kernels & instrument — `setup.geo`¶

Field	Type	Notes
`meta_kernel_file`	`Path`	Path to the mission meta-kernel JSON file
`generic_kernel_dir`	`Path`	Directory containing generic shared SPICE kernels
`dynamic_kernels`	`list[Path]`	Kernel JSONs regenerated from telemetry each iteration
`instrument_name`	`str`	SPICE instrument name as defined in the IK (e.g. `"CPRS_HYSICS"`)
`time_field`	`str`	Column in the science DataFrame holding uGPS timestamps
`minimum_correlation`	`float \| None`	Image-matching quality filter (0.0–1.0); `None` disables

Parameters — `sweep.parameters[]`¶

Field	Type	Notes
`ptype`	`ParameterType`	`CONSTANT_KERNEL`, `OFFSET_KERNEL`, or `OFFSET_TIME`
`config_file`	`Path \| None`	Path to the SPICE kernel JSON template; required for kernel types
`spec`	`ParameterSpec`	Sampling specification (see below)
`spec.current_value`	`float \| list[float]`	Baseline value(s). For `CONSTANT_KERNEL`: `[roll, pitch, yaw]`
`spec.bounds`	`[min, max]`	Offset limits in the same units as `sigma`
`spec.sigma`	`float \| None`	Sampling standard deviation for the `RANDOM` strategy
`spec.units`	`str \| None`	Physical units string, e.g. `"arcseconds"` or `"milliseconds"`
`spec.field`	`str \| None`	Telemetry column name; required for `OFFSET_KERNEL` / `OFFSET_TIME`

Parameter types — `ptype`¶

Value	Description
`CONSTANT_KERNEL`	Fixed attitude rotation applied to an instrument frame (roll/pitch/yaw offset)
`OFFSET_KERNEL`	Dynamic bias added to a telemetry angle field to regenerate a CK kernel
`OFFSET_TIME`	Timing offset applied to science frame timestamps

Search strategies — `search_strategy`¶

Value	Description
`RANDOM`	Monte Carlo: draws from a normal distribution at each iteration (default)
`GRID_SEARCH`	Cartesian product of evenly spaced grid points across all parameter bounds
`SINGLE_OFFSET`	Each parameter swept independently while all others remain at nominal values

Inputs — `inputs=`¶

Each input is format-neutral: every field is just a path, and the reader is chosen by setup.data_config.file_format. The first-class real-data path is a NetCDF image observation (radiance as the science variable) that carries telemetry, metadata, and science times — enough for curryer/SPICE to compute the geometry — so the same file commonly serves as both the telemetry and science input. See Inputs & Data Formats below.

Field	Description
`telemetry_file`	Telemetry observation file (NetCDF first-class; CSV/HDF5 read)
`science_file`	Science/timing observation file (NetCDF first-class; CSV/HDF5)
`gcp_file`	GCP reference-image file (NetCDF; `.mat` interim)

Calibration — `setup.calibration`¶

Direct calibration file paths. Both fields are optional and interim — real line-of-sight vectors and spacecraft geometry will be SPICE-derived from telemetry, so nothing in the pipeline requires these.

Field	Description
`los_vectors_file`	Per-detector line-of-sight unit vectors (instrument)
`psf_file`	Optical point-spread-function calibration

Data loading — `setup.data_config`¶

Field	Description
`file_format`	`"csv"`, `"netcdf"`, or `"hdf5"` — drives the reader for telemetry/science
`time_scale_factor`	Multiply science timestamps by this factor to obtain uGPS (e.g. `1e6` for GPS seconds)
`position_columns`	Optional list of spacecraft-position column names in the telemetry DataFrame

Inputs & Data Formats¶

The config and API are format-agnostic: the internal contract is an ImageGrid / xr.Dataset, and DataConfig.file_format selects the reader. Two distinct input families exist, and it is worth being explicit about which is which:

NetCDF image observations (first-class, intended real-data path). A NetCDF observation carries the radiance as its science variable plus the telemetry, metadata, and science times needed for curryer/SPICE to compute the line-of-sight and spacecraft geometry. This is the direction the package is built toward, and the recommended format for new missions.
.mat / file-based LOS & PSF (interim test scaffolding). The code was developed against interim .mat test fixtures — fake image arrays and standalone .mat line-of-sight / PSF files supplied via CalibrationFiles.los_vectors_file / psf_file (or verify(..., los_file=, psf_file=)). These are convenience inputs for testing without SPICE-derived geometry; they are never required and will be superseded as LOS/spacecraft geometry becomes SPICE-derived.

Real-data NetCDF ingestion (deriving geometry from observation telemetry) is the intended direction, not a claim that it is fully implemented today. Frame new work around the NetCDF-observation path and treat .mat/file-based LOS/PSF as interim.

Image-Matching Dataset Format¶

The image_matching_results passed to verify() must be a list of xr.Dataset objects with a measurement dimension. Spacecraft-state variable names are configured on GeolocationSetup.

Variable	Dimension(s)	Description
`lat_error_deg`	`[measurement]`	Latitude error (degrees, positive = northward)
`lon_error_deg`	`[measurement]`	Longitude error (degrees, positive = eastward)
`gcp_lat_deg`	`[measurement]`	GCP centre latitude (degrees)
`gcp_lon_deg`	`[measurement]`	GCP centre longitude (degrees)
`gcp_alt`	`[measurement]`	GCP altitude (metres; typically `0.0`)
`<spacecraft_position_name>`	`[measurement, xyz]`	Spacecraft position in CTRS/ITRF93 frame, metres
`<boresight_name>`	`[measurement, xyz]`	Instrument boresight unit vector in the instrument frame
`<transformation_matrix_name>`	`[measurement, xyz_from, xyz_to]`	Rotation matrix from instrument frame to CTRS

<spacecraft_position_name> corresponds to GeolocationSetup.spacecraft_position_name (and similarly for the other two). For CLARREO these are "riss_ctrs", "bhat_hs", and "t_hs2ctrs" respectively.

When spacecraft-state variables are unavailable (e.g. testing without SPICE kernels), set the boresight to the nadir unit vector (-r_sc / |r_sc|) and the rotation matrix to identity. This makes the nadir-equivalent scaling factor 1.0 and passes raw errors through unchanged — the correct conservative default.

Interpreting Results¶

Verification¶

result = verify(setup, image_matching_results=datasets)

print(result.summary_table)         # ASCII table: per-GCP pass/fail
print("Passed:", result.passed)
print(f"Within threshold: {result.percent_within_threshold:.1f}%")

for err in result.per_gcp_errors:
    print(f"GCP {err.gcp_index}: nadir_error={err.nadir_equiv_error_m:.1f} m  passed={err.passed}")

# Serialise to JSON (xr.Dataset field must be excluded)
json_str = result.model_dump_json(exclude={"aggregate_stats"})
result.aggregate_stats.to_netcdf("verification_stats.nc")

Comparing Before and After¶

from curryer.correction import compare_results

before = verify(setup, image_matching_results=pre_datasets)
after  = verify(setup, image_matching_results=post_datasets)
print(compare_results(before, after))

Correction Loop¶

result = run_correction(setup, sweep, inputs, work_dir)

print(result.summary_table)
print("Passed:", result.passed)
print(result.recommendation)

best = min(result.results, key=lambda r: r["rms_error_m"])
print(f"Best RMS: {best['rms_error_m']:.2f} m  (parameters: {best['parameters']})")

AWS / S3 Data Access¶

For missions storing image-matching results in S3 (requires boto3):

import datetime
from curryer.correction.dataio import S3Configuration, find_netcdf_objects, download_netcdf_objects

s3_config = S3Configuration(
    bucket="my-mission-bucket",
    base_prefix="image_match",   # date-partitioned subdirs: base_prefix/YYYYMMDD/
)

object_keys = find_netcdf_objects(
    s3_config,
    start_date=datetime.date(2024, 3, 17),
    end_date=datetime.date(2024, 3, 17),
)

local_paths = download_netcdf_objects(s3_config, object_keys, destination="/tmp/downloads")

Configure credentials via AWS_ACCESS_KEY_ID / AWS_SECRET_ACCESS_KEY environment variables or an IAM role. S3 support is optional; the core API works with local Path objects only.

Troubleshooting¶

KeyError: Missing required 'sweep' section The JSON config is missing a required top-level section. load_config_files() requires "setup" and "sweep"; "output" is optional.

ValidationError on requirements The setup’s requirements block must contain performance_threshold_m and performance_spec_percent. These encode the mission’s geolocation requirement and cannot be omitted.

ValidationError when loading the config The error names the offending field. Common causes: a wrong type (sigma must be a number, not a string), a missing required field (setup.geo and setup.requirements are required), or an unknown field name in a parameter’s spec (unknown keys are rejected rather than silently ignored).

SPICE(PATHTOOLONG) kernel path error SPICE enforces an 80-character kernel path limit. Curryer works around this automatically. Override the temp directory if /tmp is unavailable:

export CURRYER_TEMP_DIR=/tmp

ValueError when passing geolocated_data= to verify() The geolocated_data path needs a way to match. Either attach a callable to setup.image_matching_func, or pass gcp_directory=, los_file=, and psf_file= to use the built-in pairing + matching. (Or skip this path and pass pre-computed image_matching_results= instead.)

NaN values in nadir_equiv_total_error_m The nadir-equivalent conversion requires valid spacecraft geometry. A negative discriminant (logged as Suspicious geometry: discriminant < 0) means the off-nadir angle exceeds the Earth-limb limit — typically caused by incorrect or missing spacecraft-state variables. Verify that spacecraft_position_name, boresight_name, and transformation_matrix_name resolve to the correct variables and that the spacecraft position vector is in metres in the CTRS (Earth-fixed) frame.

Reference Examples¶

File	Status	Description
`examples/correction/example_verification.py`	Runnable	End-to-end verification demo; real CLARREO data or synthetic fallback
`examples/correction/example_run_correction.py`	Template	Correction loop template; exits cleanly when data/tools missing
`examples/correction/clarreo_config.py`	—	Mission config factory — use as a template for new missions
`examples/correction/clarreo_config.json`	—	Fully populated JSON config for CLARREO
`examples/correction/example_config.json`	—	Annotated generic JSON config template

Run from the repository root:

python examples/correction/example_verification.py
python examples/correction/example_run_correction.py

GCP Chip Regridding¶

Ground Control Point (GCP) reference imagery (e.g. Landsat imagery) is often in HDF format, in which each pixel’s position is stored as Earth-Centered, Earth-Fixed (ECEF) X/Y/Z coordinates on an irregular geodetic grid. Before these chips can be matched against L1A science images for verification and correction purposes, they must be resampled onto a regular latitude/longitude grid that matches the spatial resolution of the mission’s detector.

The curryer.correction package provides a complete pipeline for this:

HDF chip  →  ECEF → WGS84 geodetic  →  bilinear regrid  →  regular NetCDF grid

Quick start — single file (Python)¶

from pathlib import Path
from curryer.correction.config import RegridConfig
from curryer.correction.image_io import load_gcp_chip_from_hdf
from curryer.correction.regrid import regrid_gcp_chip

# 1. Load raw chip (returns band data + ECEF X/Y/Z arrays)
band, ecef_x, ecef_y, ecef_z = load_gcp_chip_from_hdf(
    Path("LT08CHP.20140803.p002r071.c01.v001.hdf")
)

# 2. Configure regridding (~100 m resolution for CLARREO)
config = RegridConfig(output_resolution_deg=(0.0009, 0.0009))

# 3. Regrid and save in one call
regridded = regrid_gcp_chip(
    band,
    (ecef_x, ecef_y, ecef_z),
    config,
    output_file="regridded_chip.nc",
    output_metadata={
        "source_file": "LT08CHP.20140803.p002r071.c01.v001.hdf",
        "mission": "CLARREO Pathfinder",
        "sensor": "Landsat-8",
        "band": "red",
    },
)

# 4. regridded is an ImageGrid — ready for image matching
print(regridded.data.shape)   # e.g. (421, 433)
print(regridded.lat[0, 0])    # top-left latitude

Batch processing — command-line script¶

For a directory of 100 Landsat chips use the provided script directly:

# Regrid all *.hdf files in /data/landsat_gcps/ and write NetCDF to /data/regridded/
python examples/correction/regrid_gcp_chips.py /data/landsat_gcps/ /data/regridded/

Output:

Processing 100 file(s) → /data/regridded/

[ 1/100] START LT08CHP.20140101.p002r071.c01.v001.hdf
         ✓ LT08CHP.20140101.p002r071.c01.v001_regridded.nc  (1823 KB, 4.2s)
[ 2/100] START LT08CHP.20140116.p002r071.c01.v001.hdf
         ✓ LT08CHP.20140116.p002r071.c01.v001_regridded.nc  (1791 KB, 4.0s)
...
────────────────────────────────────────────────────────────
Finished: all 100 file(s) processed successfully.

Common options¶

Flag	Default	Description
`--resolution DLAT DLON`	`0.0009 0.0009`	Output resolution in degrees (~100 m)
`--pattern GLOB`	`*.hdf`	Filename pattern when source is a directory
`--mission NAME`	`CLARREO Pathfinder`	Written to NetCDF `mission` attribute
`--band DATASET`	`Band_1`	HDF dataset name for the radiometric channel
`--skip-existing`	off	Skip files whose output `.nc` already exists
`--dry-run`	off	Print what would be done, write nothing
`--no-conservative-bounds`	off	Use full ECEF extent (may include edge artefacts)
`-v` / `--verbose`	off	Show per-row progress and DEBUG log output

Resume an interrupted run with --skip-existing; preview before committing with --dry-run.

Batch processing — Python API¶

Use this when you need custom logic (filtering, parallel execution, etc.):

from pathlib import Path
from curryer.correction.config import RegridConfig
from curryer.correction.image_io import load_gcp_chip_from_hdf
from curryer.correction.regrid import regrid_gcp_chip

input_dir  = Path("/data/landsat_gcps")
output_dir = Path("/data/regridded")
output_dir.mkdir(parents=True, exist_ok=True)

config = RegridConfig(output_resolution_deg=(0.0009, 0.0009))

hdf_files = sorted(input_dir.glob("LT08CHP.*.hdf"))
errors = {}
for hdf_file in hdf_files:
    nc_file = output_dir / f"{hdf_file.stem}_regridded.nc"
    try:
        band, ecef_x, ecef_y, ecef_z = load_gcp_chip_from_hdf(hdf_file)
        regrid_gcp_chip(
            band, (ecef_x, ecef_y, ecef_z), config,
            output_file=str(nc_file),
            output_metadata={"source_file": hdf_file.name, "mission": "CLARREO Pathfinder"},
        )
        print(f"  ✓ {hdf_file.name}")
    except Exception as exc:
        errors[hdf_file.name] = str(exc)
        print(f"  ✗ {hdf_file.name}: {exc}")

Loading regridded output¶

from pathlib import Path
from curryer.correction.image_io import load_image_grid

gcp = load_image_grid(Path("regridded_chip.nc"))
# gcp.data  — 2-D radiometric values
# gcp.lat   — 2-D latitude  (regular grid, decreasing from top to bottom)
# gcp.lon   — 2-D longitude (regular grid, increasing left to right)
# gcp.h     — 2-D height above WGS84 ellipsoid (metres), or None

Configuration reference¶

from curryer.correction.config import RegridConfig

config = RegridConfig(output_resolution_deg=(0.0009, 0.0009))   # resolution-based (most common)
config = RegridConfig(output_grid_size=(500, 500))               # fixed output size
config = RegridConfig(                                           # explicit extent + resolution
    output_bounds=(-116.5, -115.5, 38.0, 39.0),   # (minlon, maxlon, minlat, maxlat)
    output_resolution_deg=(0.001, 0.001),
)

Parameter	Type	Description
`output_resolution_deg`	`(dlat, dlon)`	Grid spacing in degrees. Mutually exclusive with `output_grid_size`.
`output_grid_size`	`(nrows, ncols)`	Fixed output dimensions. Mutually exclusive with `output_resolution_deg`.
`output_bounds`	`(minlon, maxlon, minlat, maxlat)`	Explicit geographic extent. Requires `output_resolution_deg`.
`conservative_bounds`	`bool` (default `True`)	Shrink bounds to grid interior to avoid edge extrapolation.
`interpolation_method`	`"bilinear"` \| `"nearest"`	Interpolation algorithm (default `"bilinear"`).
`fill_value`	`float` (default `NaN`)	Value assigned to output points outside the input footprint.

Output NetCDF structure¶

dimensions:  y (rows), x (cols)
variables:
  band_data(y, x)   — radiometric values      [digital_number]
  lat(y, x)         — latitude                [degrees_north]
  lon(y, x)         — longitude               [degrees_east]
  h(y, x)           — height above WGS84      [metres]  (present when height is available)
global attributes:
  title, Conventions (CF-1.8), source_file, mission, band, processing_software, …

Coordinate convention: row 0 is northernmost (latitude decreases down), column 0 is westernmost (longitude increases right) — consistent with the MATLAB Chip_regrid2.m output format.

Notes:

Ellipsoid: ECEF → geodetic conversion always uses WGS84 (curryer.compute.spatial.ecef_to_geodetic).
HDF format: load_gcp_chip_from_hdf tries HDF4 (pyhdf) first, then falls back to HDF5 (h5py).
Memory: a 1400 × 1400 Landsat chip uses ~30 MB RAM; 100 chips processed sequentially stay well within a 4 GB budget.
Performance: each chip typically takes 3–6 seconds on a single CPU core.

GCP Chip Regridding

Correction & Verification User Guide¶

Quickstart¶

How a mission is configured¶

Reuse the setup, try many adjustments¶

What to provide for a new mission¶

Verification¶

Input modes¶

Correction¶

Low-level alternative: loop()¶

Loading config from JSON¶

Configuration Reference¶

Setup — setup¶

Sweep — sweep¶

Output — output¶

Requirements — setup.requirements¶

Kernels & instrument — setup.geo¶

Parameters — sweep.parameters[]¶

Parameter types — ptype¶

Search strategies — search_strategy¶

Inputs — inputs=¶

Calibration — setup.calibration¶

Data loading — setup.data_config¶

Inputs & Data Formats¶

Image-Matching Dataset Format¶

Interpreting Results¶

Verification¶

Comparing Before and After¶

Correction Loop¶

AWS / S3 Data Access¶

Troubleshooting¶

Reference Examples¶

GCP Chip Regridding¶

Quick start — single file (Python)¶

Batch processing — command-line script¶

Common options¶

Batch processing — Python API¶

Loading regridded output¶

Configuration reference¶

Output NetCDF structure¶

Low-level alternative: `loop()`¶

Setup — `setup`¶

Sweep — `sweep`¶

Output — `output`¶

Requirements — `setup.requirements`¶

Kernels & instrument — `setup.geo`¶

Parameters — `sweep.parameters[]`¶

Parameter types — `ptype`¶

Search strategies — `search_strategy`¶

Inputs — `inputs=`¶

Calibration — `setup.calibration`¶

Data loading — `setup.data_config`¶