Buffer

View inJavaKotlin
View on GitHub
Sample viewer app

Create a buffer around a map point and display the results as a Graphic.

Image of Buffer

Use case

Creating buffers is a core concept in GIS proximity analysis that allows you to visualize and locate geographic features contained within a polygon. For example, suppose you wanted to visualize areas of your city where alcohol sales are prohibited because they are within 500 meters of a school. The first step in this proximity analysis would be to generate 500 meter buffer polygons around all schools in the city. Any such businesses you find inside one of the resulting polygons are violating the law.

How to use the sample

Tap on the map. A planar and a geodesic buffer will be created at the tap location using the distance (miles) specified in the text box. Continue tapping to create additional buffers. Notice that buffers closer to the equator appear similar in size. As you move north or south from the equator, however, the geodesic polygons become much larger. Geodesic polygons are in fact a better representation of the true shape and size of the buffer. Tap Clear to remove all buffers and start again.

How it works

  1. The map Point for a tap on the display is captured.
  2. The static method GeometryEngine.buffer is called to create a planar buffer polygon from the map location and distance.
  3. Another static method, GeometryEngine.bufferGeodetic is called to create a geodesic buffer polygon using the same inputs.
  4. The polygon results (and tap location) are displayed in the map view with different symbols in order to highlight the difference between the buffer techniques due to the spatial reference used in the planar calculation.

Relevant API

  • GeometryEngine.buffer
  • GeometryEngine.bufferGeodetic
  • GraphicsOverlay

Additional information

Buffers can be generated as either planar (flat - coordinate space of the map's spatial reference) or geodesic (technique that considers the curved shape of the Earth's surface, which is generally a more accurate representation). In general, distortion in the map increases as you move away from the standard parallels of the spatial reference's projection. This map is in Web Mercator so areas near the equator are the most accurate. As you move the buffer location north or south from that line, you'll see a greater difference in the polygon size and shape. Planar operations are generally faster, but performance improvement may only be noticeable for large operations (buffering a great number or complex geometry).

For more information about using buffer analysis, see the topic How Buffer (Analysis) works in the ArcGIS Pro documentation.

Tags

analysis, buffer, euclidean, geodesic, geometry, planar

Sample Code

MainActivity.kt
                                                                                                                                                                                            
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
/* Copyright 2020 Esri
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

package com.esri.arcgisruntime.sample.buffer

import android.graphics.Color
import android.os.Bundle
import android.view.MotionEvent
import android.widget.Button
import android.widget.EditText
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity

import com.esri.arcgisruntime.ArcGISRuntimeEnvironment
import com.esri.arcgisruntime.geometry.GeodeticCurveType
import com.esri.arcgisruntime.geometry.GeometryEngine
import com.esri.arcgisruntime.geometry.LinearUnit
import com.esri.arcgisruntime.geometry.LinearUnitId
import com.esri.arcgisruntime.mapping.ArcGISMap
import com.esri.arcgisruntime.mapping.BasemapStyle
import com.esri.arcgisruntime.mapping.view.DefaultMapViewOnTouchListener
import com.esri.arcgisruntime.mapping.view.Graphic
import com.esri.arcgisruntime.mapping.view.GraphicsOverlay
import com.esri.arcgisruntime.mapping.view.MapView
import com.esri.arcgisruntime.sample.buffer.databinding.ActivityMainBinding
import com.esri.arcgisruntime.symbology.SimpleFillSymbol
import com.esri.arcgisruntime.symbology.SimpleLineSymbol
import com.esri.arcgisruntime.symbology.SimpleMarkerSymbol
import com.esri.arcgisruntime.symbology.SimpleRenderer
import kotlin.math.roundToInt

class MainActivity : AppCompatActivity() {

  private val activityMainBinding by lazy {
    ActivityMainBinding.inflate(layoutInflater)
  }

  private val mapView: MapView by lazy {
    activityMainBinding.mapView
  }

  private val bufferInput: EditText by lazy {
    activityMainBinding.bufferInput
  }

  private val clearButton: Button by lazy {
    activityMainBinding.clearButton
  }

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(activityMainBinding.root)

    // authentication with an API key or named user is required to access basemaps and other
    // location services
    ArcGISRuntimeEnvironment.setApiKey(BuildConfig.API_KEY)

    // create a map with a topographic basemap
    mapView.map = ArcGISMap(BasemapStyle.ARCGIS_TOPOGRAPHIC)

    // create a fill symbol for geodesic buffer polygons
    val geodesicOutlineSymbol = SimpleLineSymbol(SimpleLineSymbol.Style.SOLID, Color.BLACK, 2F)
    val geodesicBufferFillSymbol = SimpleFillSymbol(
      SimpleFillSymbol.Style.SOLID, Color.GREEN,
      geodesicOutlineSymbol
    )

    // create a graphics overlay to display geodesic polygons and set its renderer
    val geodesicGraphicsOverlay = GraphicsOverlay().apply {
      renderer = SimpleRenderer(geodesicBufferFillSymbol)
      opacity = 0.5f
    }

    // create a fill symbol for planar buffer polygons
    val planarOutlineSymbol = SimpleLineSymbol(SimpleLineSymbol.Style.SOLID, Color.BLACK, 2F)
    val planarBufferFillSymbol = SimpleFillSymbol(
      SimpleFillSymbol.Style.SOLID, Color.RED,
      planarOutlineSymbol
    )

    // create a graphics overlay to display planar polygons and set its renderer
    val planarGraphicsOverlay = GraphicsOverlay().apply {
      renderer = SimpleRenderer(planarBufferFillSymbol)
      opacity = 0.5f
    }

    // create a marker symbol for tap locations
    val tapSymbol = SimpleMarkerSymbol(SimpleMarkerSymbol.Style.CROSS, Color.WHITE, 14F)

    // create a graphics overlay to display tap locations for buffers and set its renderer
    val tapLocationsOverlay = GraphicsOverlay().apply {
      renderer = SimpleRenderer(tapSymbol)
    }

    // add overlays to the mapView
    mapView.graphicsOverlays.addAll(
      listOf(
        geodesicGraphicsOverlay,
        planarGraphicsOverlay,
        tapLocationsOverlay
      )
    )

    // create a buffer around the clicked location
    mapView.onTouchListener =
      object : DefaultMapViewOnTouchListener(applicationContext, mapView) {
        override fun onSingleTapConfirmed(motionEvent: MotionEvent): Boolean {

          // get the point that was clicked and convert it to a point in the map
          val screenPoint = android.graphics.Point(
            motionEvent.x.roundToInt(),
            motionEvent.y.roundToInt()
          )
          val mapPoint = mapView.screenToLocation(screenPoint)

          // only draw a buffer if a value was entered
          if (bufferInput.text.toString().isNotEmpty()) {
            // get the buffer distance (miles) entered in the text box
            val bufferInMiles = bufferInput.text.toString().toDouble()

            // convert the input distance to meters, 1609.34 meters in one mile
            val bufferInMeters = bufferInMiles * 1609.34

            // create a planar buffer graphic around the input location at the specified distance
            val bufferGeometryPlanar = GeometryEngine.buffer(mapPoint, bufferInMeters)
            val planarBufferGraphic = Graphic(bufferGeometryPlanar)

            // create a geodesic buffer graphic using the same location and distance
            val bufferGeometryGeodesic = GeometryEngine.bufferGeodetic(
              mapPoint, bufferInMeters,
              LinearUnit(LinearUnitId.METERS), Double.NaN, GeodeticCurveType.GEODESIC
            )
            val geodesicBufferGraphic = Graphic(bufferGeometryGeodesic)

            // create a graphic for the user tap location
            val locationGraphic = Graphic(mapPoint)

            // add the buffer polygons and tap location graphics to the appropriate graphic overlays
            planarGraphicsOverlay.graphics.add(planarBufferGraphic)
            geodesicGraphicsOverlay.graphics.add(geodesicBufferGraphic)
            tapLocationsOverlay.graphics.add(locationGraphic)
          } else {
            Toast.makeText(
              this@MainActivity,
              "Please enter a buffer distance first.",
              Toast.LENGTH_LONG
            ).show()
          }
          return true
        }
      }

    // clear the graphics from the graphics overlays
    clearButton.setOnClickListener {
      planarGraphicsOverlay.graphics.clear()
      geodesicGraphicsOverlay.graphics.clear()
      tapLocationsOverlay.graphics.clear()
    }
  }

  override fun onResume() {
    super.onResume()
    mapView.resume()
  }

  override fun onPause() {
    mapView.pause()
    super.onPause()
  }

  override fun onDestroy() {
    mapView.dispose()
    super.onDestroy()
  }
}

Your browser is no longer supported. Please upgrade your browser for the best experience. See our browser deprecation post for more details.