# Complete survey workflow: Example Bay

## Overview

This vignette walks through a complete oystermapR workflow using a simulated survey of Example Bay — a fictional sheltered coastal inlet with realistic physical characteristics. The full pipeline is covered:

1. Loading acoustic Doppler (ADCP) current data
2. Loading bathymetric soundings
3. Loading CTD water-quality data (temperature, salinity, chlorophyll_a, pH, alkalinity)
4. Merging all sensor datasets onto a common grid
5. Running quality control
6. Predicting suitability for Ostrea edulis (European Flat Oyster)
7. Scoring wave exposure and HAB risk
8. Exporting a five-band GeoTIFF for QGIS
9. pH and aragonite saturation scoring
10. Variable impact diagnostic
11. Fine-scale habitat area analysis
12. Tolerance curve visualisation

The example data files (`example_bay_adcp.csv`, `example_bay_soundings.xyz`, and `example_bay_ctd.csv`) are included in the package and represent a simulated mid-summer survey.

    library(oystermapR)

## Survey context

Example Bay is a sheltered inlet approximately 6 km × 4 km in extent, with depths ranging from 2 m at the shoreline to around 22 m in the central channel. A six-hour ADCP transect was run on a flood tide during June. Bathymetric soundings were collected concurrently using a single-beam echosounder.

The target species is Ostrea edulis, the European Flat Oyster, whose optimal conditions include: depths of 1–20 m, current speeds of 0.05–0.4 m/s, temperatures of 5–25°C, and salinities of 25–35 PSU.

## Step 1: Load ADCP data

`read_nortek_adcp()` reads the Nortek Signature 500 merged CSV export. It auto-detects velocity bins, spatially averages ensembles onto a grid, and derives bed shear stress from the near-bed velocity profile. The `spatial_res` argument controls the decimal places used for lat/lon grid binning; `2` gives approximately 1 km cells, suitable for a bay-scale survey.

    adcp_file <- system.file("extdata", "example_bay_adcp.csv", package = "oystermapR")

    adcp <- read_nortek_adcp(
      file        = adcp_file,
      spatial_res = 2,
      verbose     = TRUE
    )

    head(adcp[, c("lat", "lon", "current_velocity", "shear_stress")])

The output contains one row per grid cell. `current_velocity` is the mean near-bed flow magnitude; `shear_stress` is the estimated bed shear stress in N/m², used by `predict_oyster()` for suspension-feeder scoring.

## Step 2: Load bathymetric soundings

`read_soundings_xyz()` reads a space-delimited XYZ point cloud, grids and averages the depths, and derives slope and rugosity via finite differences.

    xyz_file <- system.file("extdata", "example_bay_soundings.xyz", package = "oystermapR")

    bathy <- read_soundings_xyz(
      file          = xyz_file,
      spatial_res   = 2,
      min_soundings = 5,
      verbose       = TRUE
    )

    head(bathy[, c("lat", "lon", "depth", "slope", "roughness")])

`slope` is the maximum downslope gradient in degrees at each grid cell; values above ~15° typically exclude oyster settlement in the scoring model. `roughness` is a dimensionless rugosity index (1.0 = flat; higher = more complex substrate).

## Step 3: Load CTD water-quality data

The ADCP and echosounder provide hydrodynamic and bathymetric variables, but `predict_oyster()` can also use water-quality data when available. The Example Bay survey included a 5 × 4 grid of CTD casts recording temperature, salinity, chlorophyll_a, pH, and total alkalinity, stored as a plain CSV.

`read_generic_csv()` handles any tabular sensor export with flexible column matching. Column names are recognised automatically when they follow standard conventions (`lat`/`lon`, `temperature`, `salinity`, `chlorophyll_a`, `ph`, `alkalinity`). For instruments that export non-standard headers, supply an explicit `col_map`:

    # Example with non-standard headers from a YSI EXO sonde export:
    ctd <- read_generic_csv(
      "ysi_export.csv",
      col_map = c(lat = "GPS_Lat", lon = "GPS_Lon",
                  temperature = "Temp_C", salinity = "Sal_PSU",
                  ph = "pH_total", alkalinity = "TA_umolkg")
    )

For Example Bay the column names match the oystermapR conventions directly:

    ctd_file <- system.file("extdata", "example_bay_ctd.csv", package = "oystermapR")

    ctd <- read_generic_csv(
      file        = ctd_file,
      spatial_res = 2,
      verbose     = TRUE
    )

    head(ctd[, c("lat", "lon", "temperature", "salinity", "chlorophyll_a",
                 "ph", "alkalinity")])

Spatially averaging at `spatial_res = 2` collapses the four replicate casts per station to a single value per ~1 km grid cell. The `ph` and `alkalinity` columns will be used in Step 9 for aragonite saturation scoring.

## Step 4: Merge all sensor datasets

`merge_sensor_data()` performs a full outer join of any number of sensor dataframes on rounded lat/lon grid keys. Cells present in only one source are retained with `NA` for the missing variables, so no data is discarded. All three layers — ADCP, bathymetry, and CTD — are combined in a single call:

    survey <- merge_sensor_data(adcp = adcp, bathy = bathy, ctd = ctd)

    cat("Merged survey:", nrow(survey), "grid cells\n")
    cat("Columns:", paste(names(survey), collapse = ", "), "\n")

A `substrate_hardness` column would typically come from a sidescan mosaic processed via `read_sonar_tif()`. Here we add a representative value for a mixed shell-gravel substrate, typical of productive inshore oyster ground.

    set.seed(101)
    n <- nrow(survey)
    # 0 = soft mud, 1 = hard rock; 0.3--0.7 = shell/gravel mix
    survey$substrate_hardness <- round(runif(n, 0.30, 0.70), 2)

## Step 5: Quality control

`qc_survey_data()` applies three complementary checks to every numeric column:

- Range check — values outside physically plausible bounds for that variable (species-agnostic; e.g. salinity above 42 PSU) are flagged `"range_fail"`.
- Statistical outlier — values beyond `iqr_k` × IQR from the median are flagged `"outlier"` (default k = 3, Tukey’s outer fence).
- Cross-variable sanity — physically implausible combinations (e.g. dissolved oxygen above 20 mg/L with temperature below 5°C) are flagged.

Setting `apply_flags = TRUE` replaces flagged values with `NA` so they are silently skipped downstream rather than causing erroneous scores.

    survey_clean <- qc_survey_data(
      df          = survey,
      apply_flags = TRUE,
      verbose     = TRUE
    )

    # Count any flags raised across all columns
    flag_cols <- grep("^qc_flag_", names(survey_clean), value = TRUE)
    n_flagged <- sum(sapply(survey_clean[flag_cols], function(x) sum(!is.na(x) & x != "pass")))
    cat("Total flagged values replaced with NA:", n_flagged, "\n")

The QC step is non-destructive by default (`apply_flags = FALSE`) — it adds `qc_flag_<variable>` columns so you can inspect which cells were problematic before deciding whether to exclude them.

## Step 6: Predict suitability

`predict_oyster()` applies AHP-weighted scoring rules to each available variable, combines them into a suitability score in [0, 1], and classifies locations as High / Moderate / Low / Very Low / Excluded.

    result <- predict_oyster(
      data    = survey_clean,
      species = "ostrea_edulis",
      verbose = TRUE
    )

    # Summary of suitability classes
    table(result$suitability_class)

    # Mean score and range
    cat(sprintf(
      "Suitability: mean = %.2f, range = %.2f -- %.2f\n",
      mean(result$suitability, na.rm = TRUE),
      min(result$suitability,  na.rm = TRUE),
      max(result$suitability,  na.rm = TRUE)
    ))

The result dataframe retains all input columns plus `suitability`, `suitability_class`, `data_completeness` (fraction of variables scored), `n_layers_scored` (integer count of variables contributing at each point), and per-variable component scores (`score_depth`, `score_current_velocity`, `score_ph`, `score_omega_aragonite`, etc.).

    # Points with fewer scored variables may have less reliable scores
    summary(result$n_layers_scored)
    table(result$n_layers_scored)

## Step 7: Risk and disturbance scoring

oystermapR includes optional risk modules that can be appended to the result. Here we add wave exposure (derived from the current speed data and fetch geometry) and a simple HAB risk score.

    # Wave exposure: uses current_velocity and depth as proxies for fetch exposure
    result <- score_wave_exposure(result, verbose = FALSE)

    # HAB risk: without live ICES data, scores from chlorophyll_a alone
    result <- score_hab_risk(result, verbose = FALSE)

    cat("Wave exposure range:", round(range(result$wave_exposure, na.rm=TRUE), 3), "\n")
    cat("HAB risk range:     ", round(range(result$hab_risk,      na.rm=TRUE), 3), "\n")

## Step 8: Export GeoTIFF for QGIS

`export_geotiff()` interpolates the suitability scores onto a regular raster and writes a five-band GeoTIFF. `export_qml_style()` writes a matching QGIS colour-ramp style file (`.qml`) so the layer renders immediately with the standard oystermapR colour scheme (red = excluded, green = high suitability).

    # Write five-band GeoTIFF and companion QGIS style file
    export_geotiff(
      df         = result,
      path       = "example_bay_suitability.tif",
      resolution = 0.001,
      contours   = TRUE
    )
    export_qml_style("example_bay_suitability.tif")

Load `example_bay_suitability.tif` into QGIS via Layer → Add Layer → Add Raster Layer, then right-click the layer and choose Load Layer Style to apply the `.qml` file.

The GeoTIFF contains five bands:

Band | Name | Description
--- | --- | ---
1 | `suitability` | Continuous score [0, 1]
2 | `excluded_mask` | 1 = hard-excluded by a threshold
3 | `n_observations` | Survey points per raster cell
4 | `dist_to_nearest_m` | Distance to nearest survey point (m)
5 | `n_layers_scored` | Number of variables contributing to the score

Band 5 is particularly useful as a data-coverage overlay: cells where only 2–3 variables were scored are visually distinguishable from cells with full data.

## Inspecting component scores

The result dataframe includes a `score_<variable>` column for every variable that was scored. Comparing these helps diagnose which environmental factor is the main limiting constraint at a site.

    score_cols <- grep("^score_", names(result), value = TRUE)
    # Mean component score per variable (higher = more suitable)
    col_means <- sort(colMeans(result[score_cols], na.rm = TRUE))
    print(round(col_means, 3))

Variables scoring consistently below 0.5 are the main limiting factors for Ostrea edulis at this site. Scores near 1.0 indicate that variable is not constraining growth.

## Step 9: pH and aragonite saturation scoring

pH and aragonite saturation state (Ω_arag) are scored for all 17 species. If `ph` and `alkalinity` are present in the merged survey data, `predict_oyster()` computes `omega_aragonite` automatically via `calculate_aragonite()` before the scoring step — no manual pre-processing is needed.

    # Verify aragonite was auto-calculated and scored
    "omega_aragonite"  %in% names(result)      # column present
    "score_ph"         %in% names(result)      # pH scored
    "score_omega_aragonite" %in% names(result) # aragonite scored

    # Distribution of omega_aragonite across Example Bay
    summary(result$omega_aragonite)

If your sensor does not record alkalinity, you can estimate Ω_arag from typical open-ocean values for your region and supply it as a pre-computed column, or omit it — the scoring model will redistribute its weight across remaining variables.

    # Manual calculation: sensors gave pH only, alkalinity approximated
    df$alkalinity <- 2300   # µmol/kg — representative NE Atlantic value
    df$omega_aragonite <- calculate_aragonite(
      pH          = df$ph,
      alkalinity  = df$alkalinity,
      temperature = df$temperature,
      salinity    = df$salinity
    )

## Step 10: Variable impact diagnostic

`variable_impact()` summarises the contribution of each environmental variable to the suitability score across the dataset. It is the primary QA tool for understanding model behaviour and planning future surveys.

    impact <- variable_impact(result, "ostrea_edulis")
    print(impact)

The output columns are:

- `norm_weight_pct` — the variable’s share of the total AHP weight at a typical fully-observed point.
- `mean_score` — average per-variable score across non-excluded points. Values below ~0.5 identify environmental bottlenecks at this site.
- `mean_contribution` — `norm_weight_pct × mean_score / 100`. The net weighted contribution to the suitability score. Highest-impact variables have both high weight and high score.
- `pct_coverage` — percentage of non-excluded points where this variable was observed (non-NA). Low values indicate data sparsity.

    # Variables scoring below 0.5 are potential site limiters
    impact[impact$mean_score < 0.5, c("variable", "norm_weight_pct", "mean_score")]

    # Variables with sparse data coverage
    impact[impact$pct_coverage < 80, c("variable", "pct_coverage")]

Use `sort_by = "pct_coverage"` to prioritise sensor deployment for the next survey, or `sort_by = "mean_score"` to focus on the worst-performing variables.

## Step 11: Fine-scale habitat area analysis

`area_summary()` converts the point-based result into habitat area estimates at sub-hectare resolution. This is especially useful for restoration planning, where the difference between 200 m² and 800 m² of suitable habitat is operationally significant.

    # Auto-estimate cell size from median nearest-neighbour spacing
    s <- area_summary(result, verbose = TRUE)

The function prints a concise summary to the console. The returned list contains three elements:

    # Per-class breakdown
    s$class_summary[, c("class", "area_m2", "area_ha", "pct_total_area",
                        "mean_suitability")]

    # Totals
    s$total[c("surveyed_area_m2", "suitable_area_m2", "pct_suitable", "cell_size_m")]

    # Contiguous patches of High + Moderate suitability
    head(s$patches)

    # Patches meeting the OSPAR 100 m² viable area threshold
    viable <- s$patches[s$patches$viable, ]
    cat(nrow(viable), "viable patches; largest:", round(max(viable$area_m2)), "m²\n")

For ROV or AUV surveys with a known fixed grid resolution, supply it explicitly to avoid auto-estimation error:

    # 5 m ROV grid survey
    s5m <- area_summary(result, cell_size_m = 5, viable_area_m2 = 100)

    # 25 m ADCP trackline survey, larger minimum viable unit for production scale
    s25m <- area_summary(result, cell_size_m = 25, viable_area_m2 = 500)

## Step 12: Tolerance curve visualisation

`plot_tolerance()` draws the mathematical scoring function for any scored variable directly from the species tolerance parameters — no dataset required. This is useful for QA (confirming threshold values match published literature), stakeholder reporting (“here is exactly what the model rewards”), and creating publication-quality figures.

    # Temperature scoring curve with zone shading
    plot_tolerance("ostrea_edulis", "temperature")

    # All four seasons overlaid on a single plot
    plot_tolerance("ostrea_edulis", "temperature", season = "all")

    # Ocean acidification variables
    plot_tolerance("ostrea_edulis", "ph")
    plot_tolerance("ostrea_edulis", "omega_aragonite")

    # Dissolved oxygen: compare tolerance between species
    plot_tolerance("ostrea_edulis",        "dissolved_oxygen")
    plot_tolerance("crassostrea_iredalei", "dissolved_oxygen")

Curves are colour-coded: green background = optimal zone, orange = acceptable/poor, red = hard-excluded. Dashed red vertical lines show the exclusion thresholds. The function returns a `ggplot2` object invisibly, so it can be saved or modified:

    p <- plot_tolerance("ostrea_edulis", "salinity")
    ggplot2::ggsave("salinity_tolerance_O_edulis.png", p, width = 8, height = 5)

For data-driven response curves showing how the model actually responded to observed covariate values in this survey, use `sensitivity_analysis()` instead.

## Next steps

- Validation — if you have historical presence/absence records for the site, pass them to `validate_against_records()` to calculate AUC, TSS, F1, and Brier score against model predictions.
- Bayesian tolerance updating — `update_species_tolerances()` can refine the O. edulis scoring parameters from field observations at this site.
- Multi-species comparison — run the same workflow for `"magallana_gigas"` and call `compare_species()` to see which species is better suited to each grid cell. Useful for restoration target selection.
- Sensitivity analysis — `sensitivity_analysis()` produces partial dependence curves showing how suitability varies with each variable at the observed covariate values in this survey (data-driven, contrast to `plot_tolerance()` which is parameter-driven).
- Live data — `fetch_live_environmental_data()` can replace the simulated temperature and salinity with real-time CMEMS model output or ICES observational data; see `?oystermapR_live_config` for credential setup.

## Session info

    sessionInfo()