Create a buffer around a map point and display the results as a Graphic.
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
The map Point for a tap on the display is captured.
The static method GeometryEngine.buffer is called to create a planar buffer polygon from the map location and distance.
Another static method, GeometryEngine.bufferGeodetic is called to create a geodesic buffer polygon using the same inputs.
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.
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/* Copyright 2022 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.arcgismaps.sample.createplanarandgeodeticbuffers
import android.os.Bundle
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import androidx.databinding.DataBindingUtil
import androidx.lifecycle.lifecycleScope
import com.arcgismaps.ApiKey
import com.arcgismaps.geometry.GeodeticCurveType
import com.arcgismaps.geometry.GeometryEngine
import com.arcgismaps.geometry.LinearUnit
import com.arcgismaps.geometry.LinearUnitId
import com.arcgismaps.mapping.ArcGISMap
import com.arcgismaps.mapping.BasemapStyle
import com.arcgismaps.mapping.symbology.SimpleFillSymbol
import com.arcgismaps.mapping.symbology.SimpleFillSymbolStyle
import com.arcgismaps.mapping.symbology.SimpleLineSymbol
import com.arcgismaps.mapping.symbology.SimpleLineSymbolStyle
import com.arcgismaps.mapping.symbology.SimpleMarkerSymbol
import com.arcgismaps.mapping.symbology.SimpleMarkerSymbolStyle
import com.arcgismaps.mapping.symbology.SimpleRenderer
import com.arcgismaps.mapping.view.Graphic
import com.arcgismaps.mapping.view.GraphicsOverlay
import com.arcgismaps.ArcGISEnvironment
import com.arcgismaps.Color
import com.esri.arcgismaps.sample.createplanarandgeodeticbuffers.databinding.ActivityMainBinding
import kotlinx.coroutines.launch
classMainActivity : AppCompatActivity() {
overridefunonCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
// authentication with an API key or named user is// required to access basemaps and other location services ArcGISEnvironment.apiKey = ApiKey.create(BuildConfig.API_KEY)
// set up data binding for the activityval activityMainBinding: ActivityMainBinding =
DataBindingUtil.setContentView(this, R.layout.activity_main)
// get the views from the layoutval mapView = activityMainBinding.mapView
val bufferInput = activityMainBinding.bufferInput
val clearButton = activityMainBinding.clearButton
// add mapview to the lifecycle lifecycle.addObserver(mapView)
// create a map with a topographic basemap mapView.map = ArcGISMap(BasemapStyle.ArcGISTopographic)
// create a fill symbol for geodesic buffer polygonsval geodesicOutlineSymbol = SimpleLineSymbol(SimpleLineSymbolStyle.Solid, Color.black, 2F)
val geodesicBufferFillSymbol = SimpleFillSymbol(
SimpleFillSymbolStyle.Solid, Color.green,
geodesicOutlineSymbol
)
// create a graphics overlay to display geodesic polygons and set its rendererval geodesicGraphicsOverlay = GraphicsOverlay().apply {
renderer = SimpleRenderer(geodesicBufferFillSymbol)
opacity = 0.5f }
// create a fill symbol for planar buffer polygonsval planarOutlineSymbol = SimpleLineSymbol(SimpleLineSymbolStyle.Solid, Color.black, 2F)
val planarBufferFillSymbol = SimpleFillSymbol(
SimpleFillSymbolStyle.Solid, Color.red,
planarOutlineSymbol
)
// create a graphics overlay to display planar polygons and set its rendererval planarGraphicsOverlay = GraphicsOverlay().apply {
renderer = SimpleRenderer(planarBufferFillSymbol)
opacity = 0.5f }
// create a marker symbol for tap locationsval tapSymbol = SimpleMarkerSymbol(SimpleMarkerSymbolStyle.Cross, Color.white, 14F)
// create a graphics overlay to display tap locations for buffers and set its rendererval 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 lifecycleScope.launch {
mapView.onSingleTapConfirmed.collect { event ->
// get map point tapped, return if nullval mapPoint = event.mapPoint ?: return@collect// only draw a buffer if a value was enteredif (bufferInput.text.toString().isNotEmpty()) {
// get the buffer distance (miles) entered in the text boxval bufferInMiles = bufferInput.text.toString().toDouble()
// convert the input distance to meters, 1609.34 meters in one mileval bufferInMeters = bufferInMiles * 1609.34// create a planar buffer graphic around the input location at the specified distanceval bufferGeometryPlanar = GeometryEngine.buffer(mapPoint, bufferInMeters)
val planarBufferGraphic = Graphic(bufferGeometryPlanar)
// create a geodesic buffer graphic using the same location and distanceval bufferGeometryGeodesic =
GeometryEngine.bufferGeodetic(
mapPoint, bufferInMeters,
LinearUnit(LinearUnitId.Meters), Double.NaN, GeodeticCurveType.Geodesic
)
val geodesicBufferGraphic = Graphic(bufferGeometryGeodesic)
// create a graphic for the user tap locationval 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()
}
}
}
// clear the graphics from the graphics overlays clearButton.setOnClickListener {
planarGraphicsOverlay.graphics.clear()
geodesicGraphicsOverlay.graphics.clear()
tapLocationsOverlay.graphics.clear()
}
}
}