Annual shallow-water depth estimates, for planning where the boat goes.
A depth layer for your area of interest, with a map of where it can be trusted, to scope coverage before a vessel is sent.
Spec table
- GSD
- High, 0.5–2 m
- Cadence
- Annual
- Platform
- High-res satellite
- Spectral
- Multispectral
- Output
- depth estimate layer, reliability map, planning export
- Delivery unit
- one area of interest per scope
- Units
- depth in metres, vertical reference stated in the file
- Status
- planning estimate, not a sounding
01The files
- No.
- 01
- File
- Depth estimate layer
- Format
- GeoTIFF
- What's in it
- One layer for your area of interest, refreshed once a year. Each pixel holds an estimated depth in metres, and the vertical reference is stated in the file so you can check it against your chart datum before it goes near a plan. Pixels where no depth could be estimated are left empty, not filled. Open it beside your soundings and charted depths.
- Cadence
- Once a year
- No.
- 02
- File
- Reliability coverage map
- Format
- GeoPackage
- What's in it
- Polygons marking where optical depth estimation can be relied on and where it cannot: turbid water, water too deep for light to reach the bottom, wave-disturbed surface. Cadence follows the depth layer, once a year. Use it to decide where an estimate is enough for planning and where a vessel is still needed.
- Cadence
- Once a year
- No.
- 03
- File
- Planning export
- Format
- GeoPackage or shapefile
- What's in it
- A GIS-ready layer cut for survey coverage planning, with the area of interest as the boundary. It loads into QGIS or ArcGIS next to your existing coverage polygons, so the survey plan and the priority list can be drawn on top of it. Cadence is once a year, with the other two files.
- Cadence
- Once a year
02How it works
Send the area
Supply the area of interest as a shapefile or GeoPackage. If you have soundings in the area, say so now.
Source the imagery
We pick high-res multispectral imagery from the year for clear, calm-water conditions and tell you how much of the area it covers.
Estimate depth
Depth is estimated from how blue and green light fade through the water, using spectral regression, in water where light reaches the bottom.
Hand over
The depth layer, the reliability map and the planning export come back, ready to open in your GIS. Next year's pass is added the same way.
03Limits
Each of these is flagged in the reliability map, not left for you to find.
- Condition
- Water clarity decides everything
- Effect on the output
- Turbid water cuts the depth light reaches and degrades the estimate.
- What the delivery does
- Where the water is too cloudy, the map says the estimate is unreliable and gives no depth.
- Condition
- Shallow water only
- Effect on the output
- The method works where light reaches the seabed.
- What the delivery does
- Deeper water is left out of the estimate rather than guessed at.
- Condition
- Waves and glint
- Effect on the output
- A wave-disturbed or glinting surface reduces reliability.
- What the delivery does
- The imagery is chosen for calm conditions, and a year with none leaves gaps.
- Condition
- 0.5–2 m is the floor
- Effect on the output
- A pixel is between half a metre and two metres across. A narrow shoal or a small isolated rock may cover only a pixel or two and may not show.
- What the delivery does
- Treat a first look at shallow patches as a prompt to send a boat, not a finding.
- Condition
- Annual, not on demand
- Effect on the output
- One refresh a year.
- What the delivery does
- It tells you nothing about a storm last week or a channel that shifted since.
- Condition
- An estimate, not a sounding
- Effect on the output
- Estimated depths carry an uncertainty that varies with clarity and bottom type.
- What the delivery does
- This site does not state a figure. Navigation charts still need a survey run to the standard your office works to.
04Why this exists
Planning the programme starts from the chart: areas ranked by how old or thin the sounding coverage is and how much traffic uses them. For the nearshore strip, the reefs and the approaches nobody has sounded recently, the choice is a launch into water it may not be safe in, or a gap carried into the next cycle. Airborne lidar fills some of them, as a procurement of its own. This puts a depth estimate on the whole area before the vessel days are allocated, and marks the stretches where it cannot help.
Who it's for
05Who it's for
- Survey planners and hydrographic officers who allocate vessel days and need to see where coverage is thin.
- Hydrographic data analysts who open the layer beside existing soundings and want it flagged where it can't be trusted.
- Offshore surveyors scoping a nearshore area before mobilising.
- Anyone checking a survey plan for shallow gaps before the vessel days are committed.
Who it's not for
- Teams that need a chart-ready depth. That takes a survey run to your office's standard.
- Navigation, where a skipper picks a route from the number. An estimate is not for that.
- Deep water or murky estuaries. Light does not reach the bottom there.
- Real-time or event-driven mapping after a storm. The cadence is annual.
06Questions from survey offices
Does this replace a hydrographic survey?
No. It helps you decide where to send the boat. A chart still needs a sounding run to your standard.
How deep does it work?
Only as deep as light reaches the bottom. In clear water that is a limited depth, in turbid water much less, and the reliability map shows where.
Does water clarity matter?
Yes, a great deal. Turbid or wave-disturbed water reduces reliability and the map marks it.
What resolution can I expect?
Pixels of 0.5–2 m on the ground. Features smaller than a couple of pixels will not resolve.
How current is it?
Annual, with imagery picked for calm, clear conditions where the year allows.
How do we check it against our own soundings?
Load your sounding points over the layer and compare. Tell us where your soundings are when the area is scoped, and they can be set beside the estimate.
What vertical reference are the depths in?
The reference is stated in the layer, so you can check it against your chart datum before using it.
Who owns what you deliver?
Ownership and use terms for the delivered layers are written into the contract before work starts. The imagery archives keep their own licences.
Which file formats do you deliver?
GeoTIFF for the depth layer, GeoPackage for the reliability map, and GeoPackage or shapefile for the planning export. All open in QGIS and ArcGIS.
How is it priced?
Each area is scoped and quoted on its own. You get a written scope you can take through procurement.
Send us the area and we will tell you what the imagery can cover.
Or .