Contour Mapping Tool

1. Overview

The iEnvi Contour Mapping Tool generates professional contour maps from environmental monitoring data, directly in your browser. It is designed for environmental consultants who need to visualise groundwater levels, contamination plumes, or soil data for site assessments and reports.

Key capabilities:

• Paste well data (Name, Easting, Northing, Value) and generate contour maps in seconds
• Five interpolation methods suited to different data types and well counts
• Basemap options for georeferenced data, including a high-resolution default imagery source plus global fallback layers
• Export to PNG, SVG, GeoJSON, KML, and Google Earth for reports and GIS
• Built-in QA validation (RMSE, MAE, R²) for defensible reporting
• AI analysis integration for automated interpretation

2. Quick Start

The fastest way to see the tool in action:

1. Click Example Data: Groundwater or Example Data: Contamination at the top of the page
2. Click Generate/Refresh Map
3. Your contour map appears with satellite imagery, contour lines, data point labels, and a colour legend

To use your own data, paste it into the text area in Step 1 and follow the guided workflow.

3. Step 1 — Paste Your Data

Paste your monitoring data into the text box. The tool expects four columns:

• Name — Well or sample ID (e.g. MW01, BH03)
• Easting (X) — X coordinate (MGA easting, longitude, or local grid)
• Northing (Y) — Y coordinate (MGA northing, latitude, or local grid)
• Value — The measured value (elevation in mAHD, concentration in µg/L, etc.)

Accepted Formats

• Space, tab, or comma-separated values
• Header row and units are recommended for clearer value-scale and legend labels, but the tool can usually parse data without them
• Below-detection values: use <50 format and the tool will apply your LOR handling preference
• Minimum 3 data points required; best results with 6+ points

Coordinate Systems

The tool automatically detects your coordinate system:

• MGA (GDA94) / GDA2020 MGA — Australian projected coordinates. GDA2020 is selected when the site location includes GDA2020 or MGA 2020; otherwise standard MGA is treated as GDA94
• OSGB / British National Grid — 2-letter grid references (e.g. TQ 301 800) are auto-detected. For numeric eastings/northings, include OSGB in your column headers (e.g. Easting_OSGB) or enter a UK location in Step 3
• Irish Grid — 1-letter grid references (e.g. O 123 456) are auto-detected. For numeric ITM/TM65 coordinates, include Irish or ITM in your column headers or enter an Ireland location in Step 3
• NZTM2000 — Auto-detected from the distinctive New Zealand easting/northing range
• Swiss Grid CH1903+ / LV95 — Auto-detected from the distinctive Swiss easting/northing range
• Latitude/Longitude — Decimal degrees or DMS format
• Local/Cartesian — Arbitrary coordinates (no satellite basemap available)

4. Step 2 — Select Data Type

Choose the type of data you are mapping. This affects the recommended interpolation method, colour scheme, and default settings.

• Auto-Detect — The tool infers the type from your data range and distribution
• Groundwater Elevation — Water table levels in mAHD or mBGL. Uses Kriging by default for smooth hydraulic surfaces. Enables flow direction calculation
• Groundwater Contamination — Dissolved-phase concentrations (µg/L, mg/L). Uses IDW by default to capture localised plumes. Enables plume decay and zero-boundary options
• Soil Contamination — Soil sample concentrations (mg/kg). Similar to groundwater contamination but adapted for soil context
• Custom — Any other numeric data (elevation surveys, pH, temperature, etc.)

5. Step 3 — Site Location (Optional)

Enter your site location (e.g. “London, UK”, “Taren Point, NSW”, or “MGA Zone 55”). This serves three purposes:

• Coordinate system detection — Numeric OSGB and Irish grid coordinates overlap with other systems (e.g. UTM). Including a country or keyword here (e.g. UK, British, OSGB, Ireland, ITM) ensures the correct system is detected. Alternatively, include the system name in your column headers (e.g. Easting_OSGB)
• MGA Zone hint — If your data is in MGA coordinates, specifying the zone here (e.g. MGA Zone 55) avoids the zone selection pop-up during export. Use GDA2020 to select GDA2020 datum instead of GDA94
• AI context — When using the AI Analysis feature, the location helps the AI identify nearby receptors, waterways, and land use

6. Step 4 — Data Validation

Once valid data is pasted, the tool automatically validates and displays:

• Points — Number of valid data points parsed
• Range — Minimum to maximum value in your dataset
• Type — The detected or selected data type
• Interval — The auto-suggested contour interval (you can override this in settings)

7. Generating Your Map

Click Generate/Refresh Map to create your contour map. The tool will:

1. Parse and validate your data
2. Detect the coordinate system and load a basemap when georeferenced coordinates are available
3. Run the selected interpolation method across a grid
4. Draw contour lines at the specified interval
5. Apply colour shading, labels, scale bar, and north arrow
6. Calculate QA statistics (RMSE, MAE, R²)

After the map generates, you can adjust any setting and click Generate/Refresh Map again to update.

8. Interpolation Methods

Interpolation estimates values between your measured points to create a continuous surface. Choose the method that best suits your data.

IDW (Inverse Distance Weighting)

Weights nearby points inversely by distance. Closer points have more influence. Best for contamination plumes with localised hotspots.

• When to use: Contamination data, localised features, irregular point spacing
• IDW Power (p): Controls how sharply influence drops with distance. p=2 (default) is standard. Higher values (3–6) create tighter “bullseye” patterns around points
• Plume Decay (k): Applies exponential decay with distance from high-value points. Use 0 for conservative contaminants (PFAS, metals), 0.015–0.03 for petroleum hydrocarbons

Kriging (Geostatistical)

Uses spatial correlation (variogram) to make statistically optimal predictions. Honours data points exactly and provides the most defensible surface for groundwater.

• When to use: Groundwater elevation, gentle regional trends, 6+ wells
• Models: Spherical (general purpose), Exponential (slower sill approach), Gaussian (very smooth)

RBF (Radial Basis Function)

Fits smooth mathematical surfaces through data points using Gaussian basis functions. Good all-rounder.

• When to use: General-purpose smooth interpolation, no strong assumptions about data

Planar + Kriging Blend

Combines a simple planar trend with kriging detail. The blend slider controls the mix.

• When to use: Limited wells (3–10) where pure kriging may over-fit
• Blend slider: 0% = pure planar (straight contours), 100% = pure kriging (full geostatistical)

Planar (3 Wells)

Fits a single flat plane through your data points. Produces straight, parallel contour lines.

• When to use: Only 3–5 wells, or when you need a simple planar representation

9. Map Settings & Appearance

Click the Map Settings & Appearance panel to expand all customisation options. These are grouped into sections.

Grid Resolution

Controls the density of the interpolation grid (default: 150). Higher values produce smoother contours but take longer to process.

• 50–100: Fast preview, slightly jagged contours
• 150: Good balance (recommended)
• 200–300: Very smooth, may be slow on large datasets

Boundary Style

Controls how the map handles the area beyond your data points:

• Full Rectangle: Fills the entire map extent (default)
• Natural Fade: Gradually fades out from data points
• Convex Hull: Only interpolates within the outermost points
• Distance-Based: Fades based on proximity to the nearest data point

Extrapolation %

How far beyond your data extent the map should extend (default: 8%). Increase for more context; decrease to tightly crop around your wells.

10. Contour Line Settings

• Interval: The value spacing between contour lines (e.g. 0.1 for groundwater, 100 for contamination). Leave blank for auto-calculation
• Colour: Line colour for all contours (default: dark grey #666666)
• Width: Line thickness in pixels (0.5–5, default: 1)
• Label Size: Font size for value labels drawn on contour lines (6–14, default: 9)

Contour labels are automatically placed along each visible contour line (1–3 per line), avoiding overlap with well labels.

11. Data Point Settings

• Symbol: Visual marker at each well location — Dot (filled circle), Circle + Crosshair, or Crosshair only
• Colour: Colour of point symbols and labels (default: dark grey)
• Size: Radius of the point symbol (1–10, default: 4)
• Label Size: Font size for well names and values (6–14, default: 8)

Each well displays up to two labels: the well name (e.g. MW01) above the symbol, and the measured value below. Both can be toggled independently.

12. Colour Fill & Shading

Colour fill adds a visual heatmap between contour lines. Two modes are available:

Auto Gradient

A continuous colour gradient from minimum to maximum value. Choose from pre-built palettes:

• Contamination — Clear → Yellow → Red (standard environmental)
• Viridis — Colourblind-safe perceptual palette
• Turbo — Blue → Red modern heatmap
• Single-colour — Orange, Blue, Green, Red, Purple (white → colour)
• GYR — Green → Yellow → Red (traffic light)
• Custom — Pick any base colour

Manual Colour Bands

Define discrete ranges with custom colours and labels. Ideal for reports that require specific assessment criteria.

• Click Auto Set to populate default HSL-based bands
• Click + Add Band to add custom ranges
• Each band has: Min value, Max value, Colour picker, and Label

13. Show/Hide Elements

Toggle map elements on or off:

• Data Points: Well location symbols
• Point Names: Well IDs (MW01, BH03, etc.)
• Point Values: Measured values at each well
• Contour Lines: The interpolated contour lines
• Contour Labels: Value labels placed along contour lines
• Scale Bar: Distance scale reference
• North Arrow: Cardinal direction indicator
• Flow Direction: Inferred groundwater flow arrow calculated from the hydraulic gradient (groundwater data only)

14. Technical Parameters

Decimal Places

Number of decimal places for all displayed values. Leave blank for auto-detection from your input data.

LOR Handling (Limit of Reporting)

How to treat below-detection values (e.g. <50):

• ½ LOR Value: Use half the detection limit (standard practice, e.g. <50 becomes 25)
• Full LOR Value: Use the full limit value (conservative, e.g. <50 becomes 50)
• Zero (0): Replace with zero (use with caution)

Outlier σ (Sigma)

Statistical threshold for identifying outliers. Default is 3σ (three standard deviations). Lower values are more aggressive at flagging outliers. For groundwater data, outliers are detected from the spatial residual of a planar fit; for contamination, from the raw value distribution.

Apply Smoothing

Post-processing Gaussian smoothing to reduce jagged contour edges. Enabled by default. Disable for raw interpolation output.

Exclude Outliers

Automatically removes statistical outliers from the interpolation. Excluded wells appear as grey symbols on the map.

Add Zero Boundary

Adds a ring of virtual zero-value points around your site to constrain the plume extent and prevent edge artefacts. Essential for contamination mapping.

Constrain Plume Extent

Prevents IDW from spreading contamination beyond low-value boundary wells. Disable only if the true plume extent is genuinely unknown.

Boundary Distance (m)

Distance in metres outside the data extent where zero-boundary points are placed. Default: 10m.

“White Out” Below Value

Any interpolated value below this threshold is rendered as transparent/white. Useful for removing background noise from contamination maps.

15. Map Controls & Info Bar

Info Bar

Below the map, a summary bar displays:

• Wells: Total points (with outlier count if applicable)
• Range: Data value range
• Flow: Inferred flow direction in degrees (groundwater only, when enabled)
• Gradient: Hydraulic gradient value (groundwater only)
• Interval: The contour interval used

Zoom Control

Adjust the map scale from 40% to 250%. The map re-renders at the new zoom level when changed.

Scale Bar

Displays the map scale in metres or kilometres, auto-calculated from your coordinate system and zoom level.

North Arrow

Indicates north direction. For MGA and Lat/Lon coordinates, this is true geographic north.

Flow Direction Arrow

A purple arrow showing the inferred groundwater flow direction, calculated from the overall hydraulic gradient of your water table surface. Only available for groundwater elevation data.

16. Exporting Your Map

After generating a map, the export toolbar appears with these options:

PNG (Transparent Background)

Downloads the map at 5× resolution with a transparent background. Includes scale bar, north arrow and flow direction arrow if enabled. Ideal for overlaying onto report figures or presentations.

PNG+BG (White Background)

Downloads the map at 5× resolution with a solid white background and basemap aerial (if loaded). Includes scale bar, north arrow, flow direction arrow and colour legend if enabled. All exports are ultra high-res for sharp report figures.

Shot View

Opens a clean, full-screen view of the map in a new browser tab, including the satellite basemap, scale bar, north arrow, legend and all map elements. Use your browser’s screenshot tool or right-click to save.

SVG (Vector)

Downloads a scalable vector format file. Useful for further editing in design software.

GeoJSON

Downloads contour lines and data points as a GeoJSON FeatureCollection. Supported georeferenced projected systems are automatically converted to WGS84 (longitude/latitude) for GIS compatibility. Import into QGIS, ArcGIS, or any GIS platform.

KML / Google Earth

Downloads a KML/KMZ file for use in Google Earth. KMZ is used whenever bundled assets are needed, such as custom well markers or plume overlays. The Google Earth button downloads the file and opens Google Earth Web in a new tab — drag and drop it into the Earth window.

Nearmap KML

Downloads a Nearmap-compatible KML file using pure vector data only (no embedded images or assets). The plume is exported as filled contour-band polygons with colour fills, wells use a built-in map icon, and contour lines are standard vectors. This format works reliably in Nearmap, QGIS, ArcGIS, and other platforms that do not support KMZ-embedded assets or GroundOverlay elements.

QA JSON

Downloads the QA Snapshot data as a JSON file for archival or automated reporting workflows.

17. AI Analysis

Click Copy for AI Analysis to prepare your map for interpretation by AI tools (Google Gemini, ChatGPT, Claude).

1. A modal opens with a pre-written analysis prompt
2. Click Download Map Image to save the map PNG
3. Click Copy Prompt to copy the analysis prompt to your clipboard
4. Open your preferred AI tool, paste the prompt, and upload the map image

The AI will provide interpretation of groundwater flow, plume extent, potential receptors, and recommendations.

18. QA Snapshot

The QA Snapshot panel appears below the map after generation. It provides a quick defensibility check for your interpolation:

• Method: The interpolation method and model used
• Contour Interval: The interval applied
• Coordinates: Detected coordinate system
• Points: Number of data points used
• Range: Min to max value
• Validation: Cross-validation statistics — RMSE, MAE, and R²
• Variogram (Kriging only): Model type, range, sill, and nugget parameters
• Excluded Wells: Names, values, and reasons for any excluded outliers

19. Glossary of Terms

20. Frequently Asked Questions