Time-series sampling

Sampling of a STRDS with vector points

The actinia REST API provides an API call to sample a space-time raster dataset (STRDS) at coordinate points. The coordinates must be specified in JSON and must use the same coordinate reference system as the project that contains the STRDS.

We will use the Unix shell and curl to access the REST API. First open a shell of choice (we use bash here) and setup the login information, the IP address and the port on which the actinia service is running, so you can simply change the IP and port if your server uses a different address:

export ACTINIA_URL=https://actinia.mundialis.de/latest
export AUTH='-u demouser:gu3st!pa55w0rd'
# other user credentials can be provided in the same way

The following example shows the synchronous API call that samples the STRDS temperature_mean_1950_2013_yearly_celsius at three different coordinates.

 JSON='{"points":[["a", "-5.095406", "38.840583"],
                  ["b", "9.9681980", "51.666166"],
                  ["c", "24.859647", "52.699099"]]}'

 curl ${AUTH} -X POST "${ACTINIA_URL}/projects/ECAD/mapsets/PERMANENT/strds/temperature_mean_1950_2013_yearly_celsius/sampling_sync" -H  "accept: application/json" -H  "content-type: application/json" -d "$JSON"

The result of the sampling is a list of time stamped values, that are located in the process_results section of the JSON response:

 {
   "accept_datetime": "2018-05-30 10:33:23.640702",
   "accept_timestamp": 1527676403.6407006,
   "api_info": {
     "endpoint": "syncephemeralstrdssamplingresource",
     "method": "POST",
     "path": "/api/v3/projects/ECAD/mapsets/PERMANENT/strds/temperature_mean_1950_2013_yearly_celsius/sampling_sync",
     "request_url": "http://actinia.mundialis.de/api/v3/projects/ECAD/mapsets/PERMANENT/strds/temperature_mean_1950_2013_yearly_celsius/sampling_sync"
   },
   "datetime": "2018-05-30 10:33:24.503297",
   "http_code": 200,
   "message": "Processing successfully finished",
   "process_chain_list": [
     {
       "1": {
         "inputs": {
           "column": "id text, x double precision, y double precision",
           "format": "point",
           "input": "/actinia/workspace/temp_db/gisdbase_1977514d0cc1415bac3a1722aa4f6e1e/.tmp/tmprpjtds__",
           "x": 2,
           "y": 3
         },
         "module": "v.in.ascii",
         "outputs": {
           "output": {
             "name": "input_points"
           }
         }
       },
       "2": {
         "flags": "rn",
         "inputs": {
           "column": "id",
           "points": "input_points",
           "strds": "temperature_mean_1950_2013_yearly_celsius@PERMANENT"
         },
         "module": "t.rast.sample",
         "outputs": {
           "output": {
             "name": "/actinia/workspace/temp_db/gisdbase_1977514d0cc1415bac3a1722aa4f6e1e/.tmp/tmpfsiu1fn1"
           }
         },
         "overwrite": true,
         "verbose": true
       }
     }
   ],
   "process_log": [
     {
       "executable": "v.in.ascii",
       "parameter": [
         "input=/actinia/workspace/temp_db/gisdbase_1977514d0cc1415bac3a1722aa4f6e1e/.tmp/tmprpjtds__",
         "format=point",
         "column=id text, x double precision, y double precision",
         "x=2",
         "y=3",
         "output=input_points"
       ],
       "return_code": 0,
       "run_time": 0.051050662994384766,
       "stderr": [
         "Scanning input for column types...",
         "Number of columns: 3",
         "Number of rows: 3",
         "Importing points...",
         "0..33..66..100",
         "Populating table...",
         "Building topology for vector map <input_points@mapset_1977514d0cc1415bac3a1722aa4f6e1e>...",
         "Registering primitives...",
         "",
         ""
       ],
       "stdout": ""
     },
     {
       "executable": "t.rast.sample",
       "parameter": [
         "strds=temperature_mean_1950_2013_yearly_celsius@PERMANENT",
         "points=input_points",
         "column=id",
         "output=/actinia/workspace/temp_db/gisdbase_1977514d0cc1415bac3a1722aa4f6e1e/.tmp/tmpfsiu1fn1",
         "-rn",
         "--o",
         "--v"
       ],
       "return_code": 0,
       "run_time": 0.7098870277404785,
       "stderr": ["..."],
       "stdout": ""
     }
   ],
   "process_results": [
     [
       "start_time",
       "end_time",
       "a",
       "b",
       "c"
     ],
     [
       "1950-01-01 00:00:00",
       "1951-01-01 00:00:00",
       "16.41218887608807",
       "8.178182155657963",
       "7.176576932923706"
     ],
     [
       "..."
     ],
     [
       "2012-01-01 00:00:00",
       "2013-01-01 00:00:00",
       "16.55121792732666",
       "8.837787912495367",
       "7.872688635520949"
     ]
   ],
   "progress": {
     "num_of_steps": 2,
     "step": 2
   },
   "resource_id": "resource_id-ff89db3c-1cae-44e1-adb5-35ce1ab994bc",
   "status": "finished",
   "time_delta": 0.8626308441162109,
   "timestamp": 1527676404.5032735,
   "urls": {
     "resources": [],
     "status": "http://actinia.mundialis.de/api/v3/resources/demouser/resource_id-ff89db3c-1cae-44e1-adb5-35ce1ab994bc"
   },
   "user_id": "demouser"
 }