Format Specifications (single band - Depth)
Depth is calculated from sound wave velocity and time travelled through the water column. Bathymetry surveys that record sound velocities through the water column provide more accurate estimates of seabed depth because variations in water density are accounted for. The time it takes for a sound wave to propagate through the water column, reflect off the seabed and reach a sensor is known as two-way travel time, which is the typical format for echo sounder data.
...
Measurement type:
...
Depth
...
File format:
...
GeoTIFF
...
File:
...
...
Data type:
...
32bit floating point
...
Data/Pixel units
...
metres
...
Band number:
...
1
...
Description:
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Distance from the seabed to sea surface in metres. Depth is a negative value which displays elevation as a positive value.
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No data value:
...
NaN
...
Valid data range:
...
[0 to –12,000]
...
Tiled with X and Y block sizes:
...
[512, 512]
...
Compression:
...
Deflate, Level-6 predictor-3
...
Pyramids:
...
Yes . Levels will be [8, 16, 32]. Compress the pyramids using deflate. Bi-linear resampling
...
Output Coordinate Reference System (CRS):
...
EPSG 4326 (geographic decimal degrees); except where source is UTM using WGS84
...
Horizontal Datum:
...
WGS84
...
H_Output Units:
...
Variable (Geographic - decimal degrees, UTM – metres)
...
Vertical Datum:
...
EGM2008 height (EPSG:3855)
...
V_Output Units:
...
metres
...
Output name:
...
filename || _OV.TIFF
Table 4. Format specifications for a single band MBES depth GeoTIFF.
Format Specifications (single band - Density)
Band 2 (future)
Density is the measure of soundings per area. The higher the density, the more robust and higher resolution the bathymetry data. In this case, density is determined by the number of soundings per node, where a node is a grouping of sounding points with similar elevation. High density bathymetry data typically occurs in the middle of the beam swath and density lowers closer to the edges of a swath.
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Measurement type:
...
MBES backscatter is measured by transmitting acoustic signals to the seafloor and analysing the strength of the returned signals, which depend on impedance contrast (hardness) and surface roughness. Higher backscatter intensity generally indicates rougher or harder surfaces. The raw data undergoes corrections for beam pattern, transmission loss, and angle of incidence. Calibration with reference areas and ground truthing with sediment or imagery samples ensures accuracy. Backscatter intensity, expressed in decibels, represents the ratio of incident and scattered waves. Processing includes georeferencing, radiometric and geometric corrections, angular dependence correction, and beam pattern adjustments, producing a backscatter mosaic and angular backscatter response curves.
Measurement type: | Backscatter |
File format: | GeoTIFF |
File: |
|
Data type: |
32bit floating point |
Data/Pixel |
units | metres |
Band number: | 1 |
Description: |
Number of soundings per cell/node. A node forms a cell in a bathymetry grid with a value displaying density, which is derived from the number of soundings within that node. Sounding density can inform optimal bathymetry data resolution.
No data value:
0
Valid data range:
[0, 65535]
Tiled with X and Y block sizes:
[512, 512]
Compression:
Deflate, Level-6 predictor-2
Pyramids:
None
Output Coordinate Reference System (CRS):
Output Coordinate Reference System (CRS): EPSG 4326 (geographic decimal degrees); except where source is UTM with WGS84 as the datum
Horizontal Datum:
WGS84
H_Output Units:
Variable (Geographic - decimal degrees, UTM – metres)
Vertical Datum:
EGM2008 height (EPSG:3855)
V_Output Units:
metres
Output name:
filename || .TIFF
Table 5. Format specifications for a single band MBES density GeoTIFF.
Format Specifications (single band – Uncertainty or Std Dev)
Band 3 (future)
Uncertainty is the measure of sounding confidence and is calculated from the distance between a sounding point and a node (a node is a grouping of points with similar elevation). The greater the value, the more uncertain is the point’s depth value. Influencing factors include depth, point density, proximity to swath edge and acquisition system horizontal and vertical uncertainties.
Measurement type:
Uncertainty
File format:
GeoTIFF (32bit floating point)
File:
Data type:
Float32
Data/Pixel Units
Uncertainty (preferred) and/or Standard Deviation (only if CUBE is used) decimals
Band number:
1
Description:
Multibeam backscatter measures the intensity of acoustic signals reflected from the seafloor, providing detailed information about its physical properties, such as composition and texture, which is essential for seafloor characterisation and habitat mapping. | |
No data value: | NaN |
Valid data range: |
Measurement type:
Hillshade
File format:
GeoTIFF
File:
Data type:
UINT8
Data/Pixel Units
unitless
Band number:
1
Description:
Hillshade
No data value:
0
Valid data range:
1-255
Tiled with X and Y block sizes:
[512, 512]
Compression:
Deflate, Level-6 predictor-3
Pyramids:
[10 to –250] | |
Tiled with X and Y block sizes: | [512, 512] |
Compression: | Deflate, Level-6 predictor-3 |
Pyramids: |
None
Output Coordinate Reference System (CRS):
EPSG 4326 (geographic decimal degrees); except where source is UTM with WGS84 as the datum
Horizontal Datum:
WGS84
H_Output Units:
Variable (Geographic - decimal degrees, UTM – metres)
Vertical Datum:
EGM2008 height (EPSG:3855)
V_Output Units:
metres
Output name:
filename || .TIFF
Table 6. Format specifications for a single band MBES uncertainty GeoTIFF.
Format Specifications (single band - Hillshade)
Hillshading is a technique for visualizing terrain determined by a light source and the slope and aspect of the elevation surface. It is a qualitative method for visualizing topography and does not give absolute elevation values. This is a derivative product of the L3 MBES Bathymetry grid (GeoTIFF).
Yes. Levels will be [8, 16, 32]. Compress the pyramids using deflate. Bi-linear resampling |
Output Coordinate Reference System (CRS): |
EPSG 4326 (geographic decimal degrees); except where source is UTM |
using WGS84 |
Horizontal Datum: | WGS84 |
H_Output Units: | Variable (Geographic - decimal degrees, UTM – metres) |
Vertical Datum:
EGM2008 height (EPSG:3855)
V_Output Units: |
dB | |
Output name: | filename || .TIFF |
Table 74. Format specifications for a single band Hillshade MBES intensity GeoTIFF.