Automatic calculation of a polygon area

cadasta/core/templatetags/filters.py

@@ -44,3 +44,24 @@ def set_parsley_sanitize(field):
     if type(field.field) == CharField:
         field.field.widget.attrs['data-parsley-sanitize'] = '1'
     return field
+
+
+@register.filter(name='format_area_metric_units')
+def set_format_area_metric_units(area):
+    area = float(area)
+    if area < 1000:
+        return format(area, '.2f') + ' m<sup>2</sup>'
+    else:
+        ha = area/10000
+        return format(ha, '.2f') + ' ha'
+
+
+@register.filter(name='format_area_imperial_units')
+def set_format_area_imperial_units(area):
+    area = float(area)
+    area_ft2 = area * 10.764
+    if area_ft2 < 4356:
+        return format(area_ft2, '.2f') + ' ft<sup>2</sup>'
+    else:
+        ac = area * 0.00024711
+        return format(ac, '.2f') + ' ac'

cadasta/core/tests/test_filters.py

@@ -81,3 +81,23 @@ def test_set_parsley_sanitize(self):
         bf = forms.BoundField(form, field, 'name')
         filters.set_parsley_sanitize(bf)
         assert bf.field.widget.attrs == {'data-parsley-sanitize': '1'}
+
+    def test_set_format_area_imperial_units(self):
+        area1 = '10004.494'
+        area2 = '10'
+        expected_value1 = '2.47 ac'
+        expected_value2 = '107.64 ft<sup>2</sup>'
+        imperial_units1 = filters.set_format_area_imperial_units(area1)
+        imperial_units2 = filters.set_format_area_imperial_units(area2)
+        assert imperial_units1 == expected_value1
+        assert imperial_units2 == expected_value2
+
+    def test_set_format_area_metric_units(self):
+        area1 = '10004.494'
+        area2 = '999'
+        expected_value1 = '1.00 ha'
+        expected_value2 = '999.00 m<sup>2</sup>'
+        metric_units1 = filters.set_format_area_metric_units(area1)
+        metric_units2 = filters.set_format_area_metric_units(area2)
+        assert metric_units1 == expected_value1
+        assert metric_units2 == expected_value2

cadasta/organization/download/shape.py

@@ -65,7 +65,7 @@ def write_features(self, ds, filename):
 
         content_type = ContentType.objects.get(app_label='spatial',
                                                model='spatialunit')
-        model_attrs = ('id', 'type')
+        model_attrs = ('id', 'type', 'area')
 
         self.write_items(
             filename, spatial_units, content_type, model_attrs)

cadasta/organization/download/xls.py

@@ -40,7 +40,7 @@ def write_locations(self):
         content_type = ContentType.objects.get(app_label='spatial',
                                                model='spatialunit')
         self.write_items(worksheet, locations, content_type,
-                         ['id', 'geometry.ewkt', 'type'])
+                         ['id', 'geometry.ewkt', 'type', 'area'])
 
     def write_parties(self):
         parties = self.project.parties.all()

cadasta/organization/tests/test_downloads.py

@@ -468,23 +468,26 @@ def test_write_features(self):
             csvreader = csv.reader(csvfile)
             for i, row in enumerate(csvreader):
                 if i == 0:
-                    assert row == ['id', 'type', 'geom_type']
+                    head = ['id', 'type', 'area', 'geom_type']
+                    assert row == head
                 if i == 1:
-                    assert row == [su1.id, su1.type, 'point']
+                    assert row == [su1.id, su1.type, '', 'point']
                 if i == 2:
-                    assert row == [su2.id, su2.type, 'linestring']
+                    assert row == [su2.id, su2.type, '', 'linestring']
                 if i == 3:
-                    assert row == [su3.id, su3.type, 'polygon']
+                    area = format(su3.area, '.2f')
+                    assert row == [su3.id, su3.type, area, 'polygon']
                 if i == 4:
-                    assert row == [su4.id, su4.type, 'multipoint']
+                    assert row == [su4.id, su4.type, '', 'multipoint']
                 if i == 5:
-                    assert row == [su5.id, su5.type, 'multilinestring']
+                    area = su5.area
+                    assert row == [su5.id, su5.type, '', 'multilinestring']
                 if i == 6:
-                    assert row == [su6.id, su6.type, 'multipolygon']
+                    assert row == [su6.id, su6.type, '', 'multipolygon']
                 if i == 7:
-                    assert row == [su7.id, su7.type, 'empty']
+                    assert row == [su7.id, su7.type, '', 'empty']
                 if i == 8:
-                    assert row == [su8.id, su8.type, 'none']
+                    assert row == [su8.id, su8.type, '', 'none']
 
         # remove this so other tests pass
         os.remove(filename)

cadasta/organization/tests/test_views_default_projects.py

@@ -422,7 +422,8 @@ def test_get_archived_project_with_org_admin(self):
         assert response.content == expected
 
     def test_get_with_overview_stats(self):
-        SpatialUnitFactory.create(project=self.project)
+        SpatialUnitFactory.create(project=self.project, geometry='SRID=4326;POLYGON \
+             ((30 10, 20 20, 20 20, 10 20, 30 10))')
         PartyFactory.create(project=self.project)
         ResourceFactory.create(project=self.project)
         ResourceFactory.create(project=self.project, archived=True)
@@ -431,7 +432,8 @@ def test_get_with_overview_stats(self):
         assert response.content == self.render_content(has_content=True,
                                                        num_locations=1,
                                                        num_parties=1,
-                                                       num_resources=1)
+                                                       num_resources=1,
+                                                       total_area=642391915500)
 
     def test_get_with_labels(self):
         file = self.get_file(

cadasta/organization/views/default.py

@@ -423,6 +423,10 @@ def get_context_data(self, **kwargs):
         members = OrderedDict(sorted(m.items(), key=lambda t: t[0]))
 
         num_locations = self.object.spatial_units.count()
+        total_area = self.object.spatial_units.aggregate(
+           Sum('area'))['area__sum']
+        if total_area:
+            context['total_area'] = total_area
         num_parties = self.object.parties.count()
         num_resources = self.object.resource_set.filter(archived=False).count()
         context['has_content'] = (

cadasta/spatial/migrations/0004_area_location_field.py

@@ -0,0 +1,37 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.10.7 on 2017-05-31 21:21
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+from django.contrib.gis.db.models.functions import Area, Transform
+
+
+def calculate_area_field(apps, schema_editor):
+    SpatialUnit = apps.get_model('spatial', 'SpatialUnit')
+    SpatialUnit.objects.exclude(geometry=None).extra(
+        where=["geometrytype(geometry) LIKE 'POLYGON'"]).update(
+        area=Area(Transform('geometry', 3857)))
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('spatial', '0003_custom_location_types'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='historicalspatialunit',
+            name='area',
+            field=models.FloatField(null=True),
+        ),
+        migrations.AddField(
+            model_name='spatialunit',
+            name='area',
+            field=models.FloatField(null=True),
+        ),
+        migrations.RunPython(
+            calculate_area_field,
+            reverse_code=migrations.RunPython.noop
+        ),
+    ]

cadasta/spatial/models.py

@@ -41,6 +41,8 @@ class SpatialUnit(ResourceModelMixin, RandomIDModel):
     # have a textual description of their location.
     geometry = GeometryField(null=True)
 
+    area = models.FloatField(null=True)
+
     # JSON attributes field with management of allowed members.
     attributes = JSONAttributeField(default={})
 
@@ -176,6 +178,14 @@ def check_extent(sender, instance, **kwargs):
         reassign_spatial_geometry(instance)
 
 
+@receiver(models.signals.pre_save, sender=SpatialUnit)
+def calculate_area(sender, instance, **kwargs):
+    geom = instance.geometry
+    from django.contrib.gis.geos.polygon import Polygon
+    if geom and isinstance(geom, Polygon) and geom.valid:
+        instance.area = geom.transform(3857, clone=True).area
+
+
 @fix_model_for_attributes
 @permissioned_model
 class SpatialRelationship(RandomIDModel):

cadasta/spatial/tests/test_models.py

@@ -181,6 +181,15 @@ def test_ui_class_name(self):
         su = SpatialUnitFactory.create()
         assert su.ui_class_name == "Location"
 
+    def test_area(self):
+        su = SpatialUnitFactory.create(geometry='SRID=4326;POLYGON \
+            ((30 10, 20 20, 20 20, 10 20, 30 10))')
+        assert su.area == 642391915473.7279
+
+    def test_area_no_geometry(self):
+        su = SpatialUnitFactory.create()
+        assert su.area is None
+
     def test_get_absolute_url(self):
         su = SpatialUnitFactory.create()
         assert su.get_absolute_url() == (

cadasta/spatial/tests/test_views_default.py

@@ -341,7 +341,8 @@ def setup_models(self):
                 'fname': 'test',
                 'fname_2': 'two',
                 'fname_3': ['one', 'three']
-            })
+            },
+            geometry='SRID=4326;POLYGON ((30 10, 40 40, 20 40, 10 20, 30 10))')
 
     def setup_template_context(self):
         return {
@@ -353,6 +354,7 @@ def setup_template_context(self):
             'is_allowed_add_location': True,
             'is_allowed_edit_location': True,
             'is_allowed_delete_location': True,
+            'area': '7700007175103.63'
         }
 
     def setup_url_kwargs(self):

cadasta/spatial/views/default.py

@@ -116,6 +116,7 @@ def get_context_data(self, *args, **kwargs):
                 pass
 
         location = context['location']
+        context['area'] = location.area
         user = self.request.user
         context['is_allowed_edit_location'] = user.has_perm('spatial.update',
                                                             location)

cadasta/templates/organization/project_dashboard.html

@@ -3,6 +3,7 @@
 {% load i18n %}
 {% load leaflet_tags %}
 {% load staticfiles %}
+{% load filters %}
 
 {% block extra_head %}
 {% leaflet_css plugins="groupedlayercontrol"%}

cadasta/templates/spatial/location_detail.html

@@ -1,6 +1,7 @@
 {% extends "spatial/location_wrapper.html" %}
 {% load i18n %}
 {% load widget_tweaks %}
+{% load filters %}
 
 {% block page_title %}{% trans "Location detail" %} | {% endblock %}
 

cadasta/xforms/tests/test_views_api.py

@@ -299,7 +299,6 @@ def test_point_upload(self):
         data = self._submission(form='submission_missing_semi')
         response = self.request(method='POST', user=self.user, post_data=data,
                                 content_type='multipart/form-data')
-
         geom = SpatialUnit.objects.get(attributes={'name': 'Missing Semi'})
         assert response.status_code == 201
         assert geom.geometry.geom_type == 'Point'