Introduction

Actinia is a REST service to process geographical data that can be managed by the GRASS GIS software system. The software is designed to expose a GRASS GIS database and many GRASS GIS [1] processing tool as REST service [2]. Hence, access to GRASS resources like raster maps, space-time raster datasets, processing and analysis modules are available via URL. In addition Actinia allows the processing of cloud based data, for example all Landsat 4-8 scenes as well as all Sentinel2A scenes in an ephemeral databases. The computational results of ephemeral processing are available via object storage as GeoTIFF files.

The actinia service consists of the actinia core that provides the basic but sophisticated processing service and actinia plugins that provide problem specific services like Sentinel 2A and Landsat NDVI computation, spatio-temporal statistical analysis and many more.

To use actinia the user must have an understanding of the GRASS GIS concept [7] of location, mapsets, raster maps, space-time datasets and modules. The URLs that provide access to the GRASS database reflect these concepts. Hence, the location, the mapset, the required raster map are part of the URL to access the service.

What is REST?

The Representational state transfer (REST) [2] is an architectural style based on HTTP [5] that uses GET [6], DELETE [6], POST [6] and PUT [6] methods to manipulate and receive resource with stateless operations.

While GET requests can be send easily from a browser, POST, PUT or DELETE request can not. To access the full potential of actinia you will need a HTTP client, that talks all HTTP communication methods.

Examples

Data management

Landsat and Sentinel2A NDVI computation

This API call will compute the NDVI of the top of athmosphere (TOAR) corrected Landsat4 scene LC80440342016259LGN00:

NDVI computation of Sentinel2A scene S2A_MSIL1C_20170212T104141_N0204_R008_T31TGJ_20170212T104138:

The results of the asynchronous computations are available as GeoTIFF file in a cloud storage for download.

Footnotes

[1]https://grass.osgeo.org/
[2](1, 2) https://en.wikipedia.org/wiki/Representational_State_Transfer
[3]https://en.wikipedia.org/wiki/CURL
[4]https://www.getpostman.com/apps
[5]https://en.wikipedia.org/wiki/Hypertext_Transfer_Protocol
[6](1, 2, 3, 4) https://en.wikipedia.org/wiki/Hypertext_Transfer_Protocol#Request_methods
[7]https://grass.osgeo.org/grass72/manuals/helptext.html#2.-background:-grass-gis-location-structure