Web Time Series Service - Specification

About

Web Time Series Service (WTSS) is a lightweight web service for handling time series data from remote sensing imagery. Given a location and a time interval you can retrieve the according time series as a JSON array of numbers.

In WTSS a coverage is a three dimensional array associate to spatial and temporal reference systems.

WTSS is based on three operations:

list_coverages: returns the list of all available coverages in the service.
describe_coverage: returns the metadata of a given coverage.
time_series: query the database for the list of values for a given location and time interval.

There are free and open source implementations based on this specification:

wtss-server: is a WTSS web server implemented in Python.
wtss.py: is a client API for Python.
wtss: is a client API for R.

Repository Organization

api: WTSS Specification using OpenAPI 3.0.
jsonschemas: JSON Schema for WTSS responses.

Overview of Service Operations

`list_coverages`

The list_coverages operation can be used as follow:

http://myserver/wtss/list_coverages

It will return a JSON document such as:

{
    "coverages": [ "mod09q1", "mod13q1" ]
}

`describe_coverage`

If you need the metadata of a given coverage you can use the describe_coverage operation as follow:

http://myserver/wtss/describe_coverage?name=mod13q1

The result of describe_coverage operation is a JSON document such as:

{
    "name": "mod13q1",
    "description": "Surface Reflectance 8-Day L3 Global 250m",
    "detail": "https://lpdaac.usgs.gov/dataset_discovery/modis/modis_products_table/mod09q1",
    "dimensions": {
        "x": {
            "name": "col_id",
            "min_idx": 0,
            "max_idx": 172799
        },
        "y": {
            "name": "row_id",
            "min_idx": 0,
            "max_idx": 86399
        },
        "t": {
            "name": "time_id",
            "min_idx": 0,
            "max_idx": 3
        }
    },
    "attributes": [{
        "name": "red",
        "description": "250m Surface Reflectance Band 1 (620–670 nm)",
        "datatype": "int16",
        "valid_range": {
            "min": -100,
            "max": 16000
        },
        "scale_factor": 0.0001,
        "missing_value": -28672
    }, {
        "name": "nir",
        "description": "250m Surface Reflectance Band 2 (841–876 nm)",
        "datatype": "int16",
        "valid_range": {
            "min": -100,
            "max": 16000
        },
        "scale_factor": 0.0001,
        "missing_value": -28672
    }, {
        "name": "quality",
        "description": "250m Reflectance Band Quality",
        "datatype": "uint16",
        "valid_range": {
            "min": 0,
            "max": 32767
        },
        "scale_factor": 1,
        "missing_value": 65535
    }],
    "spatial_extent": {
        "xmin": -180.0,
        "ymin": -90.0,
        "xmax": 180.0,
        "ymax": 90.0
    },
    "spatial_resolution": {
        "x": 0.00208334,
        "y": 0.00208334
    },
    "crs": {
        "proj4": "+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs",
        "wkt": "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\",0.01745329251994328,AUTHORITY[\"EPSG\",\"9122\"]],AUTHORITY[\"EPSG\",\"4326\"]]"
    },
    "timeline": [ "2000-02-18", "2000-03-05", "2000-03-21" ]
}

`time_series`

You can retrieve the time series for a given location through the time_series:

http://myserver/wtss/time_series?coverage=mod13q1&attributes=red,nir&longitude=-54.0&latitude=-5.0&start_date=2000-02-18&end_date=2000-03-21

The result of time_series is a JSON document such as:

{
    "result": {
        "attributes":  [
            {
                "attribute": "red",
                "values": [ 1243, 2222, 722 ]
            },
            {
                "attribute": "nir",
                "values": [ 3040, 3621, 1949 ]
            }
        ],
        "timeline": [ "2000-02-18", "2000-03-05", "2000-03-21" ],
        "coordinates": {
            "longitude": -53.998273633285685,
            "latitude": -5.001041666214564,
            "col": 60579,
            "row": 45600
        }

    },
    "query": {
        "coverage": "mod13q1",
        "attributes": [ "red", "nir" ],
        "longitude": -54,
        "latitude": -5,
        "start_date": "2000-02-18",
        "end_date": "2000-03-21"
    }
}

Building the Documentation

Requirements

The build system for the REST API documentation relies on the Node.js run-time environment:

Node.js (Version 8+).

ReDoc: generates HTML reference documentation from an OpenAPI specification file.

Build

If you have Node.js installed, please, execute the following command to install the ReDoc dependency:

$ npm install

After that, generate the documentation:

$ npm run build

The above command will create a folder named dist with the bundled file index.html. You may open it in your web browser or may serve it with an HTTP Server.

For Python developers, you can serve the HTMl with:

python3.7 -m http.server 8080 --directory dist

License

Web Time Series Service is free software; you can redistribute it and/or modify it under the terms of the MIT License; see LICENSE file for more details.