Unit 30 - PyWPS LST region zonesΒΆ

The last (fourth) version of the process will return for input region and dates, LST zones in vector format (GML), see line 17. Zones are defined on line 83 by r.recode. Raster classes are convert to vector by r.to.vect on line 96. Finally vector classes are exported into GML format on line 102 by v.out.ogr.

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import os

from pywps import Process, LiteralInput, LiteralOutput, ComplexInput, Format, ComplexOutput

__author__ = 'Martin Landa'

class ModisV4(Process):
    def __init__(self):
        inputs = [ComplexInput('region', 'Input vector region',
                               supported_formats=[
                                   Format('text/xml'), # requires QGIS WPS client
                                   Format('application/xml')]),
                  LiteralInput('start', 'Start date (eg. 2017-03-01)',
                               data_type='string'),
                  LiteralInput('end', 'End date (eg. 2017-04-01)',
                               data_type='string')]
        outputs = [ComplexOutput('zones', 'Output LST zones',
                                supported_formats=[Format('application/gml+xml')])
        ]

        super(ModisV4, self).__init__(
            self._handler,
            identifier='modis-v4',
            version='0.4',
            title="Modis process (v4)",
            abstract='The process uses the GRASS GIS to compute LST ' \
            'statistics for given period in 2017 for Germany',
            profile='',
            inputs=inputs,
            outputs=outputs,
            store_supported=True,
            status_supported=True,
            grass_location="/opt/grassdata/germany-modis"
        )

    def check_date(self, date_str):
        from datetime import datetime

        d = datetime.strptime(date_str, '%Y-%m-%d')
        if d.year != 2017:
            raise Exception("Only year 2017 allowed")

    def _handler(self, request, response):
        from subprocess import PIPE
        
        import grass.script as gs
        from grass.pygrass.modules import Module
        from grass.exceptions import CalledModuleError
        
        start = request.inputs['start'][0].data
        end = request.inputs['end'][0].data
        self.check_date(start)
        self.check_date(end)

        output = 'modis_{}'.format(os.getpid())
        
        # be silent
        os.environ['GRASS_VERBOSE'] = '0'

        Module('v.import',
               input=request.inputs['region'][0].file,
               output='poly')
        Module('g.region', vector='poly', align='c_001')
        Module('r.mask', vector='poly')
        try:
            Module('t.rast.series',
                   input='modis_c@PERMANENT',
                   output=output,
                   method='average',
                   where="start_time > '{start}' and start_time < '{end}'".format(
                       start=start, end=end
            ))
        except CalledModuleError:
            raise Exception('Unable to compute statistics')

        ret = Module('r.univar',
                     flags='ge',
                     map=output,
                     stdout_=PIPE
        )
        stats = gs.parse_key_val(ret.outputs.stdout)
        
        Module("r.recode",
               input = output,
               output = output + '_zones',
               rules = "-",
               stdin_ = """{min}:{first}:1
{first}:{median}:2
{median}:{third}:3
        {third}:{max}:4""".format(
            min=stats['min'], first=stats['first_quartile'],
            median=stats['median'], third=stats['third_quartile'],
            max=stats['max'])
        )

        Module("r.to.vect",
               flags = 'sv',
               input = output + '_zones',
               output = output + '_zones',
               type = "area")
        
        Module('v.out.ogr',
               input=output + '_zones',
               output='zones.gml',
               format='GML')

        response.outputs['zones'].file = 'zones.gml'

        return response

Sample process to download: modis_v4.py

Do not forget to import process as done in Unit 27 and restart demo PyWPS server.

Execute process:

http://localhost:5000/wps?request=Execute&service=WPS&identifier=modis-v4&version=1.0.0&datainputs=start=2017-03-01;end=2017-04-01;region=@xlink:href=http://localhost:5000/static/data/jena_boundary.gpkg

Compare with (output return as reference):

http://localhost:5000/wps?request=Execute&service=WPS&identifier=modis-v4&version=1.0.0&datainputs=start=2017-03-01;end=2017-04-01;region=@xlink:href=http://localhost:5000/static/data/jena_boundary.gpkg&responsedocument=zones=@asReference=true

../_images/qgis-result.png

Fig. 119 Example of WPS process consumption in QGIS using WPS client plugin.

It is the end (of the workshop), enjoy GRASS GIS, PyWPS (and your real life)! :-)