O2A GeoTIFF (`.sdi.tif`)

This document formerly lived on AWI Confluence and has been migrated here with only minor changes. It has been backdated.

Basics

This specification extends the commonly known GeoTIFF specification with a set of specific optimisations and metadata vocabulary that should be used, if applicable.

The GeoTIFF needs a WKT representation of a coordinate reference system that exists in the EPSG library, preferably EPSG:3031, EPSG:3995, or EPSG:4326.

Optimisations

O2A GeoTIFF files should use the smallest band types possible, for example Int16 instead of Float32 for cases where the precision of a float is either not necessary or not present in the data.

O2A GeoTIFF files should also have a block size of 512x512, and contain internal overviews. For more, see the section on dataset homogeneity.

Metadata vocabulary

Some values are mandatory, some are mandatory in specific* cases** and some are not mandatory.

Metadata Tag	Value mandatory?	Description	Example Values
Coordinate System	yes	The Coordinate System (SRS, CRS) must be written in the WKT format and must be valid against the EPSG code representation. If not, it won't be accepted.	WKT of EPSG:4326: https://epsg.io/4326.wkt
`DATE_TIME` or `DATE_TIME_START` `DATE_TIME_END`	no	Date/Time of the data, in the ISO 8601 format notation `YYYY-MM-DDThh:mm:ss+hh`. Either one timestamp (`DATE_TIME`) or two timestamps for time series (`DATE_TIME_START`, `DATE_TIME_END`). Note: Folder Naming Specifications and File Naming!	`2000-01-01T12:00:00+00` (UTC) `2000-01-01T13:00:00+01` (CET)

`PARAMETER_NAME`	no	Name of measured or calculated parameter.	`sea ice concentration` `elevation`
`PARAMETER_URN`	no	A parameter urn of the dataset as defined in registry.awi.de or built from a PANGAEA DOI.	`satellite:gcomw1:amsr2:l2:sic` `pangaea:893351:M132_bathy_data-products:M132_soundings_WGS84:multibeam`
`PARAMETER_UNIT`	no	The unit (or unit symbol) of the given parameter.	`%`, `m`, `meter`

`METHOD`	no	Name of method used for measurement (observation, ...) data.
`DEVICE`	no	Name or ID of device used for measurement (observation, ...) data.
`SOURCE`	yes	URL of data source.	https://doi.pangaea.de/10.1594/PANGAEA.893351?format=textfile
`DOI`	yes*	URL to DOI.	https://doi.pangaea.de/10.1594/PANGAEA.893351
`REGISTRY_URI` (formerly `SENSOR_URI`)	yes*	URL of a registry.awi.de handle (handle!!).	https://hdl.handle.net/10013/sensor.3a51c0c1-4822-476d-be31-9f80a9ef36e4
`LICENSE`	yes**	License of the dataset.	`MIT`, `CC BY-NC 3.0`

`PLATFORM`	no	Name of platform.	`Polarstern`
`EXPEDITION_NAME`	yes*	Name of expedition (campaign, cruise, ...) where data was gathered.	`PS001/1`
`EXPEDITION_ALIAS`	no	Alias of expedition (campaign, cruise, ...) where data was gathered.	`ARK-I/1`

`EVENT_NAME`	yes*	Name of expedition event where data was gathered. Mostly as dataset its registered in PANGAEA.	`PS001/1-0001`
`EVENT_ALIAS`	no	Alias of expedition event where data was gathered. Mostly as dataset its registered in PANGAEA.	`ARK-I/1-1`

*: mandatory only if the data set is registered in PANGAEA or alike.

**: mandatory only if different files from your whole dataset have different licenses. If licenses are identical, it will be sufficient to put this information into the corresponding layer metadata.

Examples

Metadata like in the following examples could be retrieved by using the gdalinfo command like this:

bash

gdalinfo ./path/to/file.sdi.tif

REGISTRY item

$ gdalinfo asi-AMSR2-g3125-20190521_EPSG4326.tif

Driver: GTiff/GeoTIFF
Files: asi-AMSR2-g3125-20190521_EPSG4326.tif
Size is 4268, 4268
Coordinate System is:
  PROJCS["WGS 84 / Arctic Polar Stereographic",
    GEOGCS["WGS 84",
      DATUM["WGS_1984",
        SPHEROID["WGS 84",6378137,298.257223563,
          AUTHORITY["EPSG","7030"]],
        AUTHORITY["EPSG","6326"]],
      PRIMEM["Greenwich",0,
        AUTHORITY["EPSG","8901"]],
      UNIT["degree",0.0174532925199433,
        AUTHORITY["EPSG","9122"]],
      AUTHORITY["EPSG","4326"]],
  PROJECTION["Polar_Stereographic"],
  PARAMETER["latitude_of_origin",71],
  PARAMETER["central_meridian",0],
  PARAMETER["scale_factor",1],
  PARAMETER["false_easting",0],
  PARAMETER["false_northing",0],
  UNIT["metre",1,
    AUTHORITY["EPSG","9001"]],
  AXIS["X",EAST],
  AXIS["Y",NORTH],
  AUTHORITY["EPSG","3995"]]
Origin = (-6527893.000000000000000,6882500.000000000000000)
Pixel Size = (3125.000000000000000,-3125.000000000000000)
Metadata:
  AREA_OR_POINT=Area
  grid_information=longitude-latitude grid for these data to be found at: https://seaice.uni-bremen.de/data/grid_coordinates/n3125/
  long_name=ASI Ice Concentration, Version: 5.4, 20190521, res: 3.12500, AMSR2, Region: Arctic3125
  valid_range=0, 100
  DATE_TIME=2019-05-21T00:00:00
  DEVICE=Advanced Microwave Scanning Radiometer 2 (AMSR2)
  METHOD=Advance Microwave
  SOURCE=https://seaice.uni-bremen.de/data/grid_coordinates/n3125/
  LICENSE=unknown
  PARAMETER_NAME=sea_ice_concentration
  PARAMETER_UNIT=%
  PARAMETER_URN=satellite:gcomw1:amsr2:l2:sic
  Image Structure Metadata:
  INTERLEAVE=BAND
Corner Coordinates:
Upper Left (-6527893.000, 6882500.000) (136d30'52.93"W, 15d 7'10.61"N)
Lower Left (-6527893.000,-6455000.000) ( 45d19'18.07"W, 16d55'59.58"N)
Upper Right ( 6809607.000, 6882500.000) (135d18'18.09"E, 13d58'41.21"N)
Lower Right ( 6809607.000,-6455000.000) ( 46d31'52.83"E, 15d43'36.08"N)
Center ( 140857.000, 213750.000) (146d36'57.28"E, 87d38'39.46"N)
Band 1 Block=512x512 Type=Float32, ColorInterp=Gray
  Min=0.000 Max=100.000
  Minimum=0.000, Maximum=100.000, Mean=89.065, StdDev=23.340
  NoData Value=0
  Overviews: 2134x2134, 1067x1067, 534x534, 267x267, 134x134, 67x67
Metadata:
    STATISTICS_MAXIMUM=100
    STATISTICS_MEAN=89.065134675115
    STATISTICS_MINIMUM=0.0002532234066166
    STATISTICS_STDDEV=23.340079762818

PANGAEA

A downscaled, compressed version of this example file can be downloaded here.

$ gdalinfo PANID893351_processed_EPSG4326_2016-11-15.tif

Driver: GTiff/GeoTIFF
Files: PANID893351_processed_EPSG4326_2016-11-15.tif
Size is 2409, 2385
Coordinate System is:
GEOGCRS["WGS 84",
    ENSEMBLE["World Geodetic System 1984 ensemble",
        MEMBER["World Geodetic System 1984 (Transit)"],
        MEMBER["World Geodetic System 1984 (G730)"],
        MEMBER["World Geodetic System 1984 (G873)"],
        MEMBER["World Geodetic System 1984 (G1150)"],
        MEMBER["World Geodetic System 1984 (G1674)"],
        MEMBER["World Geodetic System 1984 (G1762)"],
        MEMBER["World Geodetic System 1984 (G2139)"],
        ELLIPSOID["WGS 84",6378137,298.257223563,
            LENGTHUNIT["metre",1]],
        ENSEMBLEACCURACY[2.0]],
    PRIMEM["Greenwich",0,
        ANGLEUNIT["degree",0.0174532925199433]],
    CS[ellipsoidal,2],
        AXIS["geodetic latitude (Lat)",north,
            ORDER[1],
            ANGLEUNIT["degree",0.0174532925199433]],
        AXIS["geodetic longitude (Lon)",east,
            ORDER[2],
            ANGLEUNIT["degree",0.0174532925199433]],
    USAGE[
        SCOPE["Horizontal component of 3D system."],
        AREA["World."],
        BBOX[-90,-180,90,180]],
    ID["EPSG",4326]]
Data axis to CRS axis mapping: 2,1
Origin = (10.269998659999999,-24.201642489999998)
Pixel Size = (0.001350000000000,-0.001350000000000)
Metadata:
  ACCESS_RIGHTS=unrestricted
  AREA_OR_POINT=Area
  BSH_ID=20160057
  CALL_SIGN=DBBH
  CAMPAIGN_END=2016-12-11
  CAMPAIGN_END_LOCATION=Cape Town, South Africa
  CAMPAIGN_START=2016-11-15
  CAMPAIGN_START_LOCATION=Walvis Bay, Namibia
  CURATION_LEVEL=Basic curation
  DATE_TIME_END=2016-12-11 00:00:00
  DATE_TIME_START=2016-11-15 00:00:00
  DEPTH_TYPE=ELEVATION, Bathymetric
  DEVICE=Kongsberg EM 122 multibeam echosounder
  EVENT_NAME=M132-track
  EXPEDITION_NAME=M132
  LICENSE=CC-BY-3.0
  METHOD=multi-beam echosounders
  PARAMETER_NAME=ELEVATION
  PARAMETER_UNIT=m
  PLATFORM=Meteor
  PLATFORM_TYPE=research vessel
  PROCESSING_LEVEL=PANGAEA data processing level 3
  PROJECT_LABEL=AtlantOS
  SOURCE=https://doi.org/10.1594/PANGAEA.893351
Image Structure Metadata:
  INTERLEAVE=BAND
Corner Coordinates:
Upper Left  (  10.2699987, -24.2016425) ( 10d16'12.00"E, 24d12' 5.91"S)
Lower Left  (  10.2699987, -27.4213925) ( 10d16'12.00"E, 27d25'17.01"S)
Upper Right (  13.5221487, -24.2016425) ( 13d31'19.74"E, 24d12' 5.91"S)
Lower Right (  13.5221487, -27.4213925) ( 13d31'19.74"E, 27d25'17.01"S)
Center      (  11.8960737, -25.8115175) ( 11d53'45.87"E, 25d48'41.46"S)
Band 1 Block=512x512 Type=Int16, ColorInterp=Gray
  Min=-4672.000 Max=-760.000
  Minimum=-4672.000, Maximum=-760.000, Mean=-3556.275, StdDev=866.767
  NoData Value=32767
  Overviews: 1205x1193, 603x597, 302x299, 151x150, 76x75, 38x38, 19x19, 10x10, 5x5, 3x3, 2x2, 1x1
  Metadata:
    STATISTICS_MAXIMUM=-760
    STATISTICS_MEAN=-3556.2751387796
    STATISTICS_MINIMUM=-4672
    STATISTICS_STDDEV=866.7670126475
    STATISTICS_VALID_PERCENT=14.12

Dataset Homogeneity

A Dataset

can either be a single image, or consist of multiple images.
can show a topographic expansion of a parameter at a specific time period.
can show a topographic expansion of a parameter over a period of time (time series).

A homogeneous data structure is essential for smooth processing and clean rendering of the dataset. A dataset must therefore have the following properties:

File naming must be consistent.
Metadata keys and values must be consistent.
Pixel data type range must be consistent (e.g. Int16, Float32, ...).
NoData value must be proper set and consistent (in both pixel values and metadata entries).

File Naming

Data files follow the naming pattern <basename>_<timestamp>_EPSG<code>.sdi.tif and the Exchange Folder Specifications.

Naming Patterns explained:

<basename> can be everything not conflicting with EPSG<code> and/or <timestamp>.
<timestamp> is used to read the date on which the data was observed or recorded, or for which the data was modelled.
- Currently only date (and not time) is supported.
- Needs to be identical with date of DATE_TIME/DATE_TIME_START in GeoTIFF metadata.
- One of the following date formats are supported (for all files in one dataset):
  - YYYYMMDD
  - YYYY-MM-DD
  - YYYY_MM_DD
EPSG<code> is mandatory to allow multiple projections in one folder.

Example

bash

./path/to/data
|-- global/
|   |-- your_data_1_20210101_EPSG4326.sdi.tif
|   `-- your_data_2_20210101_EPSG4326.sdi.tif
|-- north/
|   |-- your_data_1_20210101_EPSG3995.sdi.tif
|   `-- your_data_2_20210101_EPSG3995.sdi.tif
`-- south/
    |-- your_data_1_20210101_EPSG3031.sdi.tif
    `-- your_data_2_20210101_EPSG3031.sdi.tif

Example Use Cases

Guides

Specs

O2A GeoTIFF (`.sdi.tif`)

Basics

Optimisations

Metadata vocabulary

Examples

REGISTRY item

PANGAEA

Dataset Homogeneity

File Naming

Example

O2A GeoTIFF (.sdi.tif) ​

Basics ​

Optimisations ​

Metadata vocabulary ​

Examples ​

REGISTRY item ​

PANGAEA ​

Dataset Homogeneity ​

File Naming ​

Example ​

O2A GeoTIFF (`.sdi.tif`)

Basics

Optimisations

Metadata vocabulary

Examples

REGISTRY item

PANGAEA

Dataset Homogeneity

File Naming

Example