hyperproc

Readers, topographic and BRDF correction, and optional ISOFIT atmospheric correction for airborne and satellite imaging spectrometers.

Documentation: https://fujiangji.github.io/hyperproc/

• Readers (hyperproc.open) return one xarray contract for AVIRIS-3/5/NG/Classic, NEON AOP, EMIT, PACE OCI, DESIS, EnMAP, PRISMA and Tanager: a lazy reflectance/radiance (y, x, wavelength) cube with wavelength, fwhm, good_wavelength, band_index, a CRS and GDAL transform, and the geometry layers sza, saa, vza, vaa, slope, aspect, cos_i, raa, elev where the product carries them.
• Finding granules (hyperproc.search, hyperproc.download): start from a place and a date rather than from a file you already have. Three archives answer, chosen by the (sensor, level) pair you ask for - NASA's CMR for EMIT, PACE and AVIRIS-3/-5; NEON's Data API for AOP flightlines; DLR's EOC STAC catalogue for EnMAP and DESIS - and all three return the same granule record, so the rest of a workflow does not care which one answered. Searching every archive is anonymous; only the bytes are gated, and each backend raises with its own registration address rather than failing quietly. hyperproc.archive.credentials() says which archives this process could download from without printing a secret, and can_download(sensor, level) answers that for one collection before anything is requested. NEON publishes a site-month at a time rather than a granule, so hyperproc.files opens one up into the flightlines inside. Granules carry a browse quicklook where the archive publishes one anonymously - EMIT and AVIRIS do, DLR's sit behind its sign-on, and CMR lists one for every PACE granule that was never written. PRISMA, Tanager and the AVIRIS-NG and Classic archives cannot be searched from here at all, and say where they live instead of returning an empty list, as do the levels a reader opens but no archive here publishes (DESIS L1B/L1C, NEON L3); hyperproc.archive.describe() prints all three cases. hyperproc.search_map() is the same search on a map: draw the box, click footprints to select them and to see their quicklooks, then hyperproc.download(m.selected, "data/"). Walked end to end over all thirteen collections in tests/0_src_code/search_download_tutorial.ipynb.
• Correction (hyperproc.correct): SCS+C topographic correction with a measured verdict, FlexBRDF for airborne flightline groups, seam checks between adjacent lines.
• Satellite BRDF (hyperproc.correct.nbar): one overpass cannot measure its own angular response, so the c-factor method (Roy et al. 2016) borrows the shape from MODIS MCD43A1, fetched for the scene's footprint and date and cached. Normalises to a fixed Sun and nadir view, or to the observed Sun with the view effect removed. Also available as hyperproc.atmos.process(..., stages=("ac", "brdf")); see tests/0_src_code/emit_tutorial.ipynb.
• Quality (hyperproc.quality_flags): every provider's masks folded into one uint16 bit layer with CF flag_masks/flag_meanings, so cloud, dilated_cloud, cloud_land, cldice and the rest stop being nine different questions. quality_apply masks a cube; process writes <stem>_quality.tif beside every product with the bit table in its GeoTIFF tags.
• Spectral transforms (hyperproc.spectral): a cube in, a cube out. smoothing, continuum (convex-hull removal), derivatives (Savitzky-Golay), and bands for addressing a band by wavelength rather than by number. Each works inside runs of usable bands, so no filter or hull spans a water-vapour gap.
• Spectral resampling (hyperproc.resample): one matrix, so a whole EMIT scene becomes Landsat 8 bands in 7 seconds. Name the target by resolution (step=10, fwhm=15), by explicit bands, by like=another_dataset, or by sensor="SENTINEL2A", which downloads and caches the agency's own measured response (hyperproc.spectral.srf: Sentinel-2 from ESA, Landsat 4/5/7/8/9 from USGS, PlanetScope 4/8 from published band edges). Reports the fraction of each target band the source actually measured and returns NaN instead of renormalising, and refuses to invent resolution the source does not have.
• Spectral features (hyperproc.features): a cube in, a map out. spectral_index takes a named index or a formula written over wavelengths ("(R800 - R670) / (R800 + R670)", parsed as a whitelisted expression), plus band_depth. Addressed by wavelength, so one call runs unchanged on EMIT at 285 bands, PACE at 122 and AVIRIS at 425.
• Coregistration (hyperproc.coregister): two products of the same ground rarely land on the same pixel, and cropping to a common extent aligns the corners while leaving the content offset. Phase correlation on one band measures the shift to about a tenth of a pixel, insensitive to brightness differences between sensors, and checks itself by matching tiles independently. Corrects by moving the georeferencing (exact, free) or by resampling onto the reference grid.
• Export (hyperproc.to_geotiff, hyperproc.to_envi): streamed, band-interleaved GeoTIFFs with wavelength band names, provenance JSON and internal overviews; or ENVI flat binaries whose .hdr states wavelength, fwhm and bbl as numbers, so band centres, widths and the bad-band list survive export. to_raster(..., format=) picks one, and process(format="ENVI") writes whole products that way. ENVI has no compression, so a full EMIT product is about 5.1 GB against 2.2 GB deflated.
• R-compatible smoothing (hyperproc.spline_gapfill): the published PRISMA route, despike with a port of pracma::findpeaks, mask the artefact ranges, fit a smoothing spline and gap-fill, then mask the water bands. The spline is a port of R's stats::smooth.spline, verified against R on real spectra to 1.5e-8 with an identical NaN pattern, and the despike step is bit-identical. Flags which reported bands are spline fill rather than measurement.
• Cosmetic smoothing (hyperproc.smooth_spectra, optional): removes the band-to-band structure a per-pixel retrieval leaves, the way some providers do before publishing. Never applied automatically, and recorded in the attributes.
• Atmospheric correction (hyperproc.atmos, optional): drives ISOFIT's apply_oe from any L1B radiance dataset with the sRTMnet emulator (JPL's route), 6S or libRadtran filling the look-up table (engine=, with aerosol_model= on the last two). The retrieval's own knobs are exposed where they matter: num_neighbors= (how far the atmospheric state is interpolated, per term), aot_prior_sigma= (ISOFIT's tight aerosol prior is why retrieved AOT sits below the providers'), surface= (the spectral prior, which decides dark-water pixels), and config_overrides= for anything else in the ISOFIT configuration. correct(redo="line") reworks only the interpolation, keeping the look-up tables. hyperproc.atmos.process("EMIT_L1B_RAD_....nc", "products/") runs the retrieval on the sensor grid, orthorectifies through the granule's GLT and writes <stem>_ac.tif with the retrieved AOT and water vapour beside it; the pieces (prepare_inputs, build_command, correct, read_outputs) are exposed for step-by-step use, see tests/0_src_code/emit_tutorial.ipynb.

Install

pip install hyperproc                 # readers, correction, export
pip install 'hyperproc[search]'       # + archive search and download
pip install 'hyperproc[search-map]'   # + the interactive map (ipyleaflet)
pip install 'hyperproc[brdf]'         # + Earth Engine, for the satellite BRDF route
pip install 'hyperproc[atmos]'        # + ISOFIT (pins h5py<=3.14, netCDF4<1.7.4; pulls torch and ray)
hyperproc-atmos-setup --base /data/isofit_assets   # once per machine: engines + data assets (~6 GB)
hyperproc-atmos-setup --engine LibRadTran          # optional: fetch and compile libRadtran (needs gcc, gfortran, make, gsl)
hyperproc-atmos-setup --check         # what is in place

Platforms. The core - readers, topographic and BRDF correction, spectral transforms, quality, resampling, export - runs on Linux, macOS and Windows. [atmos] is Linux and macOS only: ISOFIT pulls ray and torch, and the radiative-transfer engines need a Fortran compiler (6S) and a C toolchain with GSL (LibRadTran), neither of which builds on Windows.

Searching an archive needs no account. Downloading needs the archive's own, and all of them are free:

DLR is two doors. Both missions' files sit on one server behind one sign-on, but access is granted per mission, so an account that opens EnMAP need not open DESIS; DLR_EOC_USERNAME/DLR_EOC_PASSWORD is a shared fallback for whichever has no pair of its own. That server takes no HTTP Basic auth - it answers 403 to an Authorization header and redirects everything else to its CAS single sign-on - so download carries the login form through once per mission and keeps the session. The first sign-in may stop at an Acceptable Usage Policy; agreeing to it is yours to do, so hyperproc prints what it says rather than clicking it. Read it with hyperproc.archive.dlr.read_policy("ENMAP"), then accept it in a browser once or pass accept_policy=True.

The satellite BRDF route needs Earth Engine credentials once: earthengine authenticate. The airborne route fits its own kernel model from the flight's own angles and needs nothing.

The atmospheric-correction assets (compiled 6S, sRTMnet weights, spectral libraries) cannot ship in a wheel; hyperproc-atmos-setup fetches them with ISOFIT's own downloader into one shared base directory recorded in ~/.isofit/isofit.ini. Building 6S needs gfortran and make.

Tests

pip install 'hyperproc[test]'
pytest                      # 711 tests, ~7 minutes
pytest -m "not data"        # the 493 that need no granules
pytest -m network           # 6 more that check the archives still behave as recorded

Most tests have an answer known in advance rather than a recorded snapshot: a straight line has a flat derivative, resampling onto the grid you are already on returns the input, a planted pixel offset comes back out of the coregistration. Four groups are worth naming:

• readers - 216 cases over 24 sensor-level combinations, each checked against a recorded fingerprint (sizes, wavelengths, geometry, transform) and against physics that must hold whatever the reader does;
• the R port - hyperproc.spline_gapfill reproduces a published R pipeline, and is checked against R's own output on 40 real PRISMA spectra, checked in. Regenerate with python tests/tools/make_r_reference.py (needs R with pracma and FieldSpectroscopyCC);
• atmos - the parts that can be checked without a retrieval: the sensor table, the MODTRAN atmosphere choice, DEM tile naming, config rewriting;
• archive - 212 tests. Every search replays a recorded response from CMR, NEON and DLR, so the whole of hyperproc.search runs offline. Re-record with python tests/tools/make_archive_fixtures.py, and read the diff. The six network tests ask whether the recordings are still true, and two of them pin assumptions that would otherwise fail silently: that DLR's file server still refuses Basic auth, and that its sign-on is still a form this version can fill in.

Tests marked data open the granules in tests/data/, which are not in the repository. Everything else runs from a clean clone.

Tutorials

tests/0_src_code/ holds one executed notebook per instrument, each documenting every parameter of every call it makes: emit, enmap, desis, pace, prisma, tanager (whole-scene and windowed), and aviris3, aviris5, avirisng, avirisclassic, neon (windowed, since a flightline is too large to correct whole).

Citing

See CITATION.cff, or the "Cite this repository" button on GitHub.

License

MIT - see LICENSE.