Type safe angles and distances

demo/maps/src/jvmMain/kotlin/AngleConversion.kt

@@ -1,4 +0,0 @@
-import kotlin.math.PI
-
-fun Double.toDegrees() = this * 180 / PI
-

demo/maps/src/jvmMain/kotlin/Main.kt

@@ -23,7 +23,7 @@ import kotlin.math.PI
 import kotlin.random.Random
 
 private fun GeodeticMapCoordinates.toShortString(): String =
-    "${(latitude * 180.0 / PI).toString().take(6)}:${(longitude * 180.0 / PI).toString().take(6)}"
+    "${(latitude.degrees.value).toString().take(6)}:${(longitude.degrees.value).toString().take(6)}"
 
 
 @Composable
@@ -50,7 +50,7 @@ fun App() {
 
 
         val pointOne = 55.568548 to 37.568604
-        var pointTwo by remember { mutableStateOf(55.929444 to 37.518434) }
+        var pointTwo: Pair<Double, Double> by remember { mutableStateOf(55.929444 to 37.518434) }
         val pointThree = 60.929444 to 37.518434
         MapView(
             mapTileProvider = mapTileProvider,
@@ -59,11 +59,11 @@ fun App() {
                 inferViewBoxFromFeatures = true,
                 onViewChange = { centerCoordinates = focus },
                 onDrag = { start, end ->
-                    if (start.focus.latitude.toDegrees() in (pointTwo.first - 0.05)..(pointTwo.first + 0.05) &&
+                    if (start.focus.latitude.degrees.value in (pointTwo.first - 0.05)..(pointTwo.first + 0.05) &&
-                        start.focus.longitude.toDegrees() in (pointTwo.second - 0.05)..(pointTwo.second + 0.05)
+                        start.focus.longitude.degrees.value in (pointTwo.second - 0.05)..(pointTwo.second + 0.05)
                     ) {
-                        pointTwo = pointTwo.first + (end.focus.latitude - start.focus.latitude).toDegrees() to
+                        pointTwo = pointTwo.first + (end.focus.latitude - start.focus.latitude).degrees.value to
-                                pointTwo.second + (end.focus.longitude - start.focus.longitude).toDegrees()
+                                pointTwo.second + (end.focus.longitude - start.focus.longitude).degrees.value
                         false// returning false, because when we are dragging circle we don't want to drag map
                     } else true
                 }

maps-kt-compose/src/commonMain/kotlin/center/sciprog/maps/compose/MapFeature.kt

@@ -12,15 +12,15 @@ import androidx.compose.ui.unit.DpSize
 import androidx.compose.ui.unit.IntSize
 import androidx.compose.ui.unit.dp
 import center.sciprog.maps.coordinates.GeodeticMapCoordinates
-import center.sciprog.maps.coordinates.GmcBox
+import center.sciprog.maps.coordinates.GmcRectangle
 import center.sciprog.maps.coordinates.wrapAll
 
 public interface MapFeature {
     public val zoomRange: IntRange
-    public fun getBoundingBox(zoom: Int): GmcBox?
+    public fun getBoundingBox(zoom: Int): GmcRectangle?
 }
 
-public fun Iterable<MapFeature>.computeBoundingBox(zoom: Int): GmcBox? =
+public fun Iterable<MapFeature>.computeBoundingBox(zoom: Int): GmcRectangle? =
     mapNotNull { it.getBoundingBox(zoom) }.wrapAll()
 
 internal fun Pair<Double, Double>.toCoordinates() = GeodeticMapCoordinates.ofDegrees(first, second)
@@ -35,7 +35,7 @@ public class MapFeatureSelector(
 ) : MapFeature {
     override val zoomRange: IntRange get() = defaultZoomRange
 
-    override fun getBoundingBox(zoom: Int): GmcBox? = selector(zoom).getBoundingBox(zoom)
+    override fun getBoundingBox(zoom: Int): GmcRectangle? = selector(zoom).getBoundingBox(zoom)
 }
 
 public class MapDrawFeature(
@@ -43,9 +43,9 @@ public class MapDrawFeature(
     override val zoomRange: IntRange = defaultZoomRange,
     public val drawFeature: DrawScope.() -> Unit,
 ) : MapFeature {
-    override fun getBoundingBox(zoom: Int): GmcBox {
+    override fun getBoundingBox(zoom: Int): GmcRectangle {
         //TODO add box computation
-        return GmcBox(position, position)
+        return GmcRectangle(position, position)
     }
 }
 
@@ -56,8 +56,8 @@ public class MapPointsFeature(
     public val color: Color = Color.Red,
     public val pointMode: PointMode = PointMode.Points
 ) : MapFeature {
-    override fun getBoundingBox(zoom: Int): GmcBox {
+    override fun getBoundingBox(zoom: Int): GmcRectangle {
-        return GmcBox(points.first(), points.last())
+        return GmcRectangle(points.first(), points.last())
     }
 }
 
@@ -67,7 +67,7 @@ public class MapCircleFeature(
     public val size: Float = 5f,
     public val color: Color = Color.Red,
 ) : MapFeature {
-    override fun getBoundingBox(zoom: Int): GmcBox = GmcBox(center, center)
+    override fun getBoundingBox(zoom: Int): GmcRectangle = GmcRectangle(center, center)
 }
 
 public class MapRectangleFeature(
@@ -76,7 +76,7 @@ public class MapRectangleFeature(
     public val size: DpSize = DpSize(5.dp, 5.dp),
     public val color: Color = Color.Red,
 ) : MapFeature {
-    override fun getBoundingBox(zoom: Int): GmcBox = GmcBox(center, center)
+    override fun getBoundingBox(zoom: Int): GmcRectangle = GmcRectangle(center, center)
 }
 
 public class MapLineFeature(
@@ -85,17 +85,17 @@ public class MapLineFeature(
     override val zoomRange: IntRange = defaultZoomRange,
     public val color: Color = Color.Red,
 ) : MapFeature {
-    override fun getBoundingBox(zoom: Int): GmcBox = GmcBox(a, b)
+    override fun getBoundingBox(zoom: Int): GmcRectangle = GmcRectangle(a, b)
 }
 
 public class MapArcFeature(
-    public val oval: GmcBox,
+    public val oval: GmcRectangle,
     public val startAngle: Float,
     public val endAngle: Float,
     override val zoomRange: IntRange = defaultZoomRange,
     public val color: Color = Color.Red,
 ) : MapFeature {
-    override fun getBoundingBox(zoom: Int): GmcBox = oval
+    override fun getBoundingBox(zoom: Int): GmcRectangle = oval
 }
 
 public class MapBitmapImageFeature(
@@ -104,7 +104,7 @@ public class MapBitmapImageFeature(
     public val size: IntSize = IntSize(15, 15),
     override val zoomRange: IntRange = defaultZoomRange,
 ) : MapFeature {
-    override fun getBoundingBox(zoom: Int): GmcBox = GmcBox(position, position)
+    override fun getBoundingBox(zoom: Int): GmcRectangle = GmcRectangle(position, position)
 }
 
 public class MapVectorImageFeature(
@@ -113,7 +113,7 @@ public class MapVectorImageFeature(
     public val size: DpSize,
     override val zoomRange: IntRange = defaultZoomRange,
 ) : MapFeature {
-    override fun getBoundingBox(zoom: Int): GmcBox = GmcBox(position, position)
+    override fun getBoundingBox(zoom: Int): GmcRectangle = GmcRectangle(position, position)
 }
 
 @Composable
@@ -131,5 +131,5 @@ public class MapFeatureGroup(
     public val children: Map<FeatureId, MapFeature>,
     override val zoomRange: IntRange = defaultZoomRange,
 ) : MapFeature {
-    override fun getBoundingBox(zoom: Int): GmcBox? = children.values.mapNotNull { it.getBoundingBox(zoom) }.wrapAll()
+    override fun getBoundingBox(zoom: Int): GmcRectangle? = children.values.mapNotNull { it.getBoundingBox(zoom) }.wrapAll()
 }

maps-kt-compose/src/commonMain/kotlin/center/sciprog/maps/compose/MapFeatureBuilder.kt

@@ -11,7 +11,7 @@ import androidx.compose.ui.unit.DpSize
 import androidx.compose.ui.unit.dp
 import center.sciprog.maps.coordinates.Distance
 import center.sciprog.maps.coordinates.GeodeticMapCoordinates
-import center.sciprog.maps.coordinates.GmcBox
+import center.sciprog.maps.coordinates.GmcRectangle
 
 public typealias FeatureId = String
 
@@ -87,7 +87,7 @@ public fun MapFeatureBuilder.line(
 )
 
 public fun MapFeatureBuilder.arc(
-    oval: GmcBox,
+    oval: GmcRectangle,
     startAngle: Number,
     endAngle: Number,
     zoomRange: IntRange = defaultZoomRange,
@@ -109,7 +109,7 @@ public fun MapFeatureBuilder.arc(
 ): FeatureId = addFeature(
     id,
     MapArcFeature(
-        GmcBox.withCenter(center.toCoordinates(), radius, radius),
+        GmcRectangle.square(center.toCoordinates(), radius, radius),
         startAngle.toFloat(),
         endAngle.toFloat(),
         zoomRange,

maps-kt-compose/src/commonMain/kotlin/center/sciprog/maps/compose/MapView.kt

@@ -21,9 +21,9 @@ public data class MapViewConfig(
     val onClick: MapViewPoint.() -> Unit = {},
     val onDrag: (start: MapViewPoint, end: MapViewPoint) -> Boolean = { _, _ -> true },
     val onViewChange: MapViewPoint.() -> Unit = {},
-    val onSelect: (GmcBox) -> Unit = {},
+    val onSelect: (GmcRectangle) -> Unit = {},
     val zoomOnSelect: Boolean = true,
-    val resetViewPoint: Boolean = false
+    val resetViewPoint: Boolean = false,
 )
 
 @Composable
@@ -55,20 +55,21 @@ public fun MapView(
     )
 }
 
-internal fun GmcBox.computeViewPoint(mapTileProvider: MapTileProvider): (canvasSize: DpSize) -> MapViewPoint = { canvasSize ->
+internal fun GmcRectangle.computeViewPoint(mapTileProvider: MapTileProvider): (canvasSize: DpSize) -> MapViewPoint =
-    val zoom = log2(
+    { canvasSize ->
-        min(
+        val zoom = log2(
-            canvasSize.width.value / width,
+            min(
-            canvasSize.height.value / height
+                canvasSize.width.value / longitudeDelta.radians.value,
-        ) * PI / mapTileProvider.tileSize
+                canvasSize.height.value / latitudeDelta.radians.value
-    )
+            ) * PI / mapTileProvider.tileSize
-    MapViewPoint(center, zoom)
+        )
-}
+        MapViewPoint(center, zoom)
+    }
 
 @Composable
 public fun MapView(
     mapTileProvider: MapTileProvider,
-    box: GmcBox,
+    box: GmcRectangle,
     features: Map<FeatureId, MapFeature> = emptyMap(),
     config: MapViewConfig = MapViewConfig(),
     modifier: Modifier = Modifier.fillMaxSize(),

maps-kt-compose/src/jvmMain/kotlin/center/sciprog/maps/compose/MapTextFeature.kt

@@ -2,7 +2,7 @@ package center.sciprog.maps.compose
 
 import androidx.compose.ui.graphics.Color
 import center.sciprog.maps.coordinates.GeodeticMapCoordinates
-import center.sciprog.maps.coordinates.GmcBox
+import center.sciprog.maps.coordinates.GmcRectangle
 import org.jetbrains.skia.Font
 
 
@@ -13,7 +13,7 @@ public class MapTextFeature(
     public val color: Color,
     public val fontConfig: Font.() -> Unit,
 ) : MapFeature {
-    override fun getBoundingBox(zoom: Int): GmcBox = GmcBox(position, position)
+    override fun getBoundingBox(zoom: Int): GmcRectangle = GmcRectangle(position, position)
 }
 
 public fun MapFeatureBuilder.text(

maps-kt-compose/src/jvmMain/kotlin/center/sciprog/maps/compose/MapViewJvm.kt

@@ -30,12 +30,12 @@ private fun Color.toPaint(): Paint = Paint().apply {
 private fun IntRange.intersect(other: IntRange) = max(first, other.first)..min(last, other.last)
 
 internal fun MapViewPoint.move(deltaX: Double, deltaY: Double): MapViewPoint {
-    val newCoordinates = GeodeticMapCoordinates.ofRadians(
+    val newCoordinates = GeodeticMapCoordinates(
-        (focus.latitude + deltaY / scaleFactor).coerceIn(
+        (focus.latitude + (deltaY / scaleFactor).radians).coerceIn(
             -MercatorProjection.MAXIMUM_LATITUDE,
             MercatorProjection.MAXIMUM_LATITUDE
         ),
-        focus.longitude + deltaX / scaleFactor
+        focus.longitude + (deltaX / scaleFactor).radians
     )
     return MapViewPoint(newCoordinates, zoom)
 }
@@ -69,8 +69,8 @@ public actual fun MapView(
             features.values.computeBoundingBox(1)?.let { box ->
                 val zoom = log2(
                     min(
-                        canvasSize.width.value / box.width,
+                        canvasSize.width.value / box.longitudeDelta.radians.value,
-                        canvasSize.height.value / box.height
+                        canvasSize.height.value / box.latitudeDelta.radians.value
                     ) * PI / mapTileProvider.tileSize
                 )
                 MapViewPoint(box.center, zoom)
@@ -127,7 +127,7 @@ public actual fun MapView(
                             }
                             selectRect?.let { rect ->
                                 //Use selection override if it is defined
-                                val gmcBox = GmcBox(
+                                val gmcBox = GmcRectangle(
                                     rect.topLeft.toDpOffset().toGeodetic(),
                                     rect.bottomRight.toDpOffset().toGeodetic()
                                 )
@@ -146,8 +146,10 @@ public actual fun MapView(
                             config.onClick(MapViewPoint(dpPos.toGeodetic(), viewPoint.zoom))
                             drag(change.id) { dragChange ->
                                 val dragAmount = dragChange.position - dragChange.previousPosition
-                                val dpStart =
+                                val dpStart = DpOffset(
-                                    DpOffset(dragChange.previousPosition.x.toDp(), dragChange.previousPosition.y.toDp())
+                                    dragChange.previousPosition.x.toDp(),
+                                    dragChange.previousPosition.y.toDp()
+                                )
                                 val dpEnd = DpOffset(dragChange.position.x.toDp(), dragChange.position.y.toDp())
                                 if (!config.onDrag(
                                         MapViewPoint(dpStart.toGeodetic(), viewPoint.zoom),
@@ -232,6 +234,7 @@ public actual fun MapView(
                     feature.size,
                     center = feature.center.toOffset()
                 )
+
                 is MapRectangleFeature -> drawRect(
                     feature.color,
                     topLeft = feature.center.toOffset() - Offset(
@@ -240,6 +243,7 @@ public actual fun MapView(
                     ),
                     size = feature.size.toSize()
                 )
+
                 is MapLineFeature -> drawLine(feature.color, feature.a.toOffset(), feature.b.toOffset())
                 is MapArcFeature -> {
                     val topLeft = feature.oval.topLeft.toOffset()
@@ -252,6 +256,7 @@ public actual fun MapView(
                     drawPath(path, color = feature.color, style = Stroke())
 
                 }
+
                 is MapBitmapImageFeature -> drawImage(feature.image, feature.position.toOffset())
                 is MapVectorImageFeature -> {
                     val offset = feature.position.toOffset()
@@ -262,6 +267,7 @@ public actual fun MapView(
                         }
                     }
                 }
+
                 is MapTextFeature -> drawIntoCanvas { canvas ->
                     val offset = feature.position.toOffset()
                     canvas.nativeCanvas.drawString(
@@ -272,17 +278,20 @@ public actual fun MapView(
                         feature.color.toPaint()
                     )
                 }
+
                 is MapDrawFeature -> {
                     val offset = feature.position.toOffset()
                     translate(offset.x, offset.y) {
                         feature.drawFeature(this)
                     }
                 }
+
                 is MapFeatureGroup -> {
                     feature.children.values.forEach {
                         drawFeature(zoom, it)
                     }
                 }
+
                 is MapPointsFeature -> {
                     val points = feature.points.map { it.toOffset() }
                     drawPoints(
@@ -292,6 +301,7 @@ public actual fun MapView(
                         pointMode = feature.pointMode
                     )
                 }
+
                 else -> {
                     logger.error { "Unrecognized feature type: ${feature::class}" }
                 }

maps-kt-core/build.gradle.kts

@@ -15,4 +15,12 @@ kotlin {
     js(IR) {
         browser()
     }
+
+    sourceSets{
+        commonTest{
+            dependencies{
+                implementation(kotlin("test"))
+            }
+        }
+    }
 }

maps-kt-core/src/commonMain/kotlin/center/sciprog/maps/coordinates/Distance.kt

@@ -3,7 +3,9 @@ package center.sciprog.maps.coordinates
 import kotlin.jvm.JvmInline
 
 @JvmInline
-public value class Distance(public val kilometers: Double)
+public value class Distance(public val kilometers: Double) : Comparable<Distance> {
+    override fun compareTo(other: Distance): Int = this.kilometers.compareTo(other.kilometers)
+}
 
 public operator fun Distance.div(other: Distance): Double = kilometers / other.kilometers
 
@@ -13,5 +15,4 @@ public operator fun Distance.minus(other: Distance): Distance = Distance(kilomet
 public operator fun Distance.times(number: Number): Distance = Distance(kilometers * number.toDouble())
 public operator fun Distance.div(number: Number): Distance = Distance(kilometers / number.toDouble())
 
-
 public val Distance.meters: Double get() = kilometers * 1000

maps-kt-core/src/commonMain/kotlin/center/sciprog/maps/coordinates/Ellipsoid.kt

@@ -1,14 +0,0 @@
-package center.sciprog.maps.coordinates
-
-public class Ellipsoid(public val equatorRadius: Distance, public val polarRadius: Distance) {
-    public companion object {
-        public val WGS84: Ellipsoid = Ellipsoid(
-            equatorRadius = Distance(6378.137),
-            polarRadius = Distance(6356.7523142)
-        )
-    }
-}
-
-public val Ellipsoid.f: Double get() = (equatorRadius.kilometers - polarRadius.kilometers) / equatorRadius.kilometers
-
-public val Ellipsoid.inverseF: Double get() = equatorRadius.kilometers / (equatorRadius.kilometers - polarRadius.kilometers)

maps-kt-core/src/commonMain/kotlin/center/sciprog/maps/coordinates/GeoEllipsoid.kt

@@ -0,0 +1,72 @@
+package center.sciprog.maps.coordinates
+
+import center.sciprog.maps.coordinates.GeoEllipsoid.Companion.greatCircleAngleBetween
+import kotlin.math.*
+
+
+public class GeoEllipsoid(public val equatorRadius: Distance, public val polarRadius: Distance) {
+
+    /**
+     * Flattening https://en.wikipedia.org/wiki/Flattening
+     */
+    public val f: Double = (equatorRadius.kilometers - polarRadius.kilometers) / equatorRadius.kilometers
+
+    /**
+     * Inverse flattening
+     */
+    public val inverseF: Double = equatorRadius.kilometers / (equatorRadius.kilometers - polarRadius.kilometers)
+
+    public val eSquared: Double = 2 * f - f * f
+
+    public companion object {
+
+        public val WGS84: GeoEllipsoid = GeoEllipsoid(
+            equatorRadius = Distance(6378.137),
+            polarRadius = Distance(6356.752314245)
+        )
+
+        public val GRS80: GeoEllipsoid = GeoEllipsoid(
+            equatorRadius = Distance(6378.137),
+            polarRadius = Distance(6356.752314140)
+        )
+
+        public val sphere: GeoEllipsoid = GeoEllipsoid(
+            equatorRadius = Distance(6378.137),
+            polarRadius = Distance(6378.137)
+        )
+
+        /**
+         * https://en.wikipedia.org/wiki/Great-circle_distance
+         */
+        public fun greatCircleAngleBetween(r1: GMC, r2: GMC): Radians = acos(
+            sin(r1.latitude) * sin(r2.latitude) + cos(r1.latitude) * cos(r2.latitude) * cos(r1.longitude - r2.longitude)
+        ).radians
+    }
+}
+
+/**
+ * A radius of circle normal to the axis of the ellipsoid at given latitude
+ */
+internal fun GeoEllipsoid.reducedRadius(latitude: Angle): Distance {
+    val reducedLatitudeTan = (1 - f) * tan(latitude)
+    return equatorRadius / sqrt(1.0 + reducedLatitudeTan.pow(2))
+}
+
+
+/**
+ * Compute distance between two map points using giv
+ * https://en.wikipedia.org/wiki/Geographical_distance#Lambert's_formula_for_long_lines
+ */
+public fun GeoEllipsoid.lambertDistanceBetween(r1: GMC, r2: GMC): Distance {
+    val s = greatCircleAngleBetween(r1, r2)
+
+    val b1: Double = (1 - f) * tan(r1.latitude)
+    val b2: Double = (1 - f) * tan(r2.latitude)
+    val p = (b1 + b2) / 2
+    val q = (b2 - b1) / 2
+
+    val x = (s.value - sin(s)) * sin(p).pow(2) * cos(q).pow(2) / cos(s / 2).pow(2)
+    val y = (s.value + sin(s)) * cos(p).pow(2) * sin(q).pow(2) / sin(s / 2).pow(2)
+
+    return equatorRadius * (s.value - f / 2 * (x + y))
+}

maps-kt-core/src/commonMain/kotlin/center/sciprog/maps/coordinates/GeodeticMapCoordinates.kt

@@ -5,10 +5,15 @@ import kotlin.math.PI
 /**
  * Geodetic coordinated
  */
-public class GeodeticMapCoordinates private constructor(
+public class GeodeticMapCoordinates(
-    public val latitude: Double,
+    public val latitude: Angle,
-    public val longitude: Double,
+    longitude: Angle,
-){
+) {
+    public val longitude: Radians = longitude.radians.value.rem(PI / 2).radians
+
+    init {
+        require(latitude.radians.value in (-PI / 2)..(PI / 2)) { "Latitude $latitude is not in (-PI/2)..(PI/2)" }
+    }
 
     override fun equals(other: Any?): Boolean {
         if (this === other) return true
@@ -29,23 +34,24 @@ public class GeodeticMapCoordinates private constructor(
     }
 
     override fun toString(): String {
-        return "GeodeticCoordinates(latitude=${latitude / PI * 180} deg, longitude=${longitude / PI * 180} deg)"
+        return "GMC(latitude=${latitude.degrees.value} deg, longitude=${longitude.degrees.value} deg)"
     }
 
 
     public companion object {
-        public fun ofRadians(latitude: Double, longitude: Double): GeodeticMapCoordinates {
+        public fun ofRadians(latitude: Double, longitude: Double): GeodeticMapCoordinates =
-            require(latitude in (-PI/2)..(PI/2)) { "Latitude $latitude is not in (-PI/2)..(PI/2)" }
+            GeodeticMapCoordinates(latitude.radians, longitude.radians)
-            return GeodeticMapCoordinates(latitude, longitude.rem(PI / 2))
-        }
 
-        public fun ofDegrees(latitude: Double, longitude: Double): GeodeticMapCoordinates {
+        public fun ofDegrees(latitude: Double, longitude: Double): GeodeticMapCoordinates =
-            require(latitude in (-90.0)..(90.0)) { "Latitude $latitude is not in -90..90" }
+            GeodeticMapCoordinates(latitude.degrees.radians, longitude.degrees.radians)
-            return GeodeticMapCoordinates(latitude * PI / 180, (longitude.rem(180) * PI / 180))
-        }
     }
 }
 
+/**
+ * Short name for GeodeticMapCoordinates
+ */
+public typealias GMC = GeodeticMapCoordinates
+
 //public interface GeoToScreenConversion {
 //    public fun getScreenX(gmc: GeodeticMapCoordinates): Double
 //    public fun getScreenY(gmc: GeodeticMapCoordinates): Double

maps-kt-core/src/commonMain/kotlin/center/sciprog/maps/coordinates/GmcBox.kt

@@ -1,77 +0,0 @@
-package center.sciprog.maps.coordinates
-
-import kotlin.math.abs
-import kotlin.math.cos
-import kotlin.math.max
-import kotlin.math.min
-
-public data class GmcBox(
-    public val a: GeodeticMapCoordinates,
-    public val b: GeodeticMapCoordinates,
-) {
-    public companion object {
-        public fun withCenter(
-            center: GeodeticMapCoordinates,
-            width: Distance,
-            height: Distance,
-            ellipsoid: Ellipsoid = Ellipsoid.WGS84,
-        ): GmcBox {
-            val r = ellipsoid.equatorRadius * cos(center.latitude)
-            val a = GeodeticMapCoordinates.ofRadians(
-                center.latitude - height / ellipsoid.polarRadius / 2,
-                center.longitude - width / r / 2
-            )
-            val b = GeodeticMapCoordinates.ofRadians(
-                center.latitude + height / ellipsoid.polarRadius / 2,
-                center.longitude + width / r / 2
-            )
-            return GmcBox(a, b)
-        }
-    }
-}
-
-public val GmcBox.center: GeodeticMapCoordinates
-    get() = GeodeticMapCoordinates.ofRadians(
-        (a.latitude + b.latitude) / 2,
-        (a.longitude + b.longitude) / 2
-    )
-
-/**
- * Minimum longitude
- */
-public val GmcBox.left: Double get() = min(a.longitude, b.longitude)
-
-/**
- * maximum longitude
- */
-public val GmcBox.right: Double get() = max(a.longitude, b.longitude)
-
-/**
- * Maximum latitude
- */
-public val GmcBox.top: Double get() = max(a.latitude, b.latitude)
-
-/**
- * Minimum latitude
- */
-public val GmcBox.bottom: Double get() = min(a.latitude, b.latitude)
-
-//TODO take curvature into account
-public val GmcBox.width: Double get() = abs(a.longitude - b.longitude)
-public val GmcBox.height: Double get() = abs(a.latitude - b.latitude)
-
-public val GmcBox.topLeft: GeodeticMapCoordinates get() = GeodeticMapCoordinates.ofRadians(top, left)
-public val GmcBox.bottomRight: GeodeticMapCoordinates get() = GeodeticMapCoordinates.ofRadians(bottom, right)
-
-/**
- * Compute a minimal bounding box including all given boxes. Return null if collection is empty
- */
-public fun Collection<GmcBox>.wrapAll(): GmcBox? {
-    if (isEmpty()) return null
-    //TODO optimize computation
-    val minLat = minOf { it.bottom }
-    val maxLat = maxOf { it.top }
-    val minLong = minOf { it.left }
-    val maxLong = maxOf { it.right }
-    return GmcBox(GeodeticMapCoordinates.ofRadians(minLat, minLong), GeodeticMapCoordinates.ofRadians(maxLat, maxLong))
-}

maps-kt-core/src/commonMain/kotlin/center/sciprog/maps/coordinates/GmcCurve.kt

@@ -0,0 +1,348 @@
+package center.sciprog.maps.coordinates
+
+import center.sciprog.maps.coordinates.Angle.Companion.pi
+import center.sciprog.maps.coordinates.Angle.Companion.piDiv2
+import center.sciprog.maps.coordinates.Angle.Companion.zero
+import kotlin.math.*
+
+/**
+ * A directed straight (geodetic) segment on a spheroid with given start, direction, end point and distance.
+ * @param forward coordinate of a start point with forward direction
+ * @param backward coordinate of an end point with backward direction
+ */
+public class GmcCurve internal constructor(
+    public val forward: GmcPose,
+    public val backward: GmcPose,
+    public val distance: Distance,
+)
+
+public fun GmcCurve.reversed(): GmcCurve = GmcCurve(backward, forward, distance)
+
+/**
+ * Compute a curve alongside a meridian
+ */
+public fun GeoEllipsoid.meridianCurve(
+    longitude: Angle,
+    fromLatitude: Angle,
+    toLatitude: Angle,
+    step: Radians = 0.015.radians,
+): GmcCurve {
+    require(fromLatitude in (-piDiv2)..(piDiv2)) { "Latitude must be in (-90, 90) degrees range" }
+    require(toLatitude in (-piDiv2)..(piDiv2)) { "Latitude must be in (-90, 90) degrees range" }
+
+    fun smallDistance(from: Radians, to: Radians): Distance = equatorRadius *
+            (1 - eSquared) *
+            (1 - eSquared * sin(from).pow(2)).pow(-1.5) *
+            abs((from - to).value)
+
+    val up = toLatitude > fromLatitude
+
+    val integrateFrom: Radians
+    val integrateTo: Radians
+
+    if (up) {
+        integrateFrom = fromLatitude.radians
+        integrateTo = toLatitude.radians
+    } else {
+        integrateTo = fromLatitude.radians
+        integrateFrom = toLatitude.radians
+    }
+
+    var current = integrateFrom
+    var s = Distance(0.0)
+    while (current < integrateTo) {
+        val next = minOf(current + step, integrateTo)
+        s += smallDistance(current, next)
+        current = next
+    }
+
+    return GmcCurve(
+        forward = GmcPose(GMC(fromLatitude, longitude), if (up) zero else pi),
+        backward = GmcPose(GMC(toLatitude, longitude), if (up) pi else zero),
+        distance = s
+    )
+}
+
+/**
+ * Compute a curve alongside a parallel
+ */
+public fun GeoEllipsoid.parallelCurve(latitude: Angle, fromLongitude: Angle, toLongitude: Angle): GmcCurve {
+    require(latitude in (-piDiv2)..(piDiv2)) { "Latitude must be in (-90, 90) degrees range" }
+    val right = toLongitude > fromLongitude
+    return GmcCurve(
+        forward = GmcPose(GMC(latitude, fromLongitude), if (right) piDiv2.radians else -piDiv2.radians),
+        backward = GmcPose(GMC(latitude, toLongitude), if (right) -piDiv2.radians else piDiv2.radians),
+        distance = reducedRadius(latitude) * abs((fromLongitude - toLongitude).radians.value)
+    )
+}
+
+
+/**
+ * Taken from https://github.com/mgavaghan/geodesy
+ * https://github.com/mgavaghan/geodesy/blob/ab1c6969dc964ff34929911f055b27525909ef3f/src/main/java/org/gavaghan/geodesy/GeodeticCalculator.java#L58
+ *
+ * Calculate the destination and final bearing after traveling a specified
+ * distance, and a specified starting bearing, for an initial location. This
+ * is the solution to the direct geodetic problem.
+ *
+ * @param start starting location
+ * @return solution to the direct geodetic problem
+ */
+public fun GeoEllipsoid.curveInDirection(
+    start: GmcPose,
+    distance: Distance,
+    precision: Double = 1e-6,
+): GmcCurve {
+    val a: Distance = equatorRadius
+    val b: Distance = polarRadius
+    val aSquared: Double = a.kilometers.pow(2)
+    val bSquared: Double = b.kilometers.pow(2)
+    val phi1 = start.latitude
+    val alpha1 = start.bearing
+    val cosAlpha1: Double = cos(alpha1)
+    val sinAlpha1: Double = sin(alpha1)
+    val tanU1: Double = (1.0 - f) * tan(phi1)
+    val cosU1: Double = 1.0 / sqrt(1.0 + tanU1 * tanU1)
+    val sinU1 = tanU1 * cosU1
+
+    // eq. 1
+    val sigma1: Radians = atan2(tanU1, cosAlpha1).radians
+
+    // eq. 2
+    val sinAlpha: Double = cosU1 * sinAlpha1
+    val sin2Alpha = sinAlpha * sinAlpha
+    val cos2Alpha = 1 - sin2Alpha
+    val uSquared = cos2Alpha * (aSquared - bSquared) / bSquared
+
+    // eq. 3
+    val A: Double = 1 + uSquared / 16384 * (4096 + uSquared * (-768 + uSquared * (320 - 175 * uSquared)))
+
+    // eq. 4
+    val B: Double = uSquared / 1024 * (256 + uSquared * (-128 + uSquared * (74 - 47 * uSquared)))
+
+    // iterate until there is a negligible change in sigma
+    val sOverbA: Radians = (distance / b / A).radians
+    var sigma: Radians = sOverbA
+    var sinSigma: Double
+    var prevSigma: Radians = sOverbA
+    var sigmaM2: Radians
+    var cosSigmaM2: Double
+    var cos2SigmaM2: Double
+    while (!prevSigma.value.isNaN()) {
+        // eq. 5
+        sigmaM2 = sigma1 * 2.0 + sigma
+        cosSigmaM2 = cos(sigmaM2)
+        cos2SigmaM2 = cosSigmaM2 * cosSigmaM2
+        sinSigma = sin(sigma)
+//        val cosSigma: Double = cos(sigma)
+
+        // eq. 6
+        val deltaSigma = B * sinSigma *
+                (cosSigmaM2 + B / 4.0 * (cos(sigma) * (-1 + 2 * cos2SigmaM2) -
+                        B / 6.0 * cosSigmaM2 * (-3 + 4 * sinSigma * sinSigma) * (-3 + 4 * cos2SigmaM2)))
+
+        // eq. 7
+        sigma = sOverbA + deltaSigma.radians
+
+        // break after converging to tolerance
+        if (abs((sigma - prevSigma).value) < precision) break
+        prevSigma = sigma
+    }
+    sigmaM2 = sigma1 * 2.0 + sigma
+    cosSigmaM2 = cos(sigmaM2)
+    cos2SigmaM2 = cosSigmaM2 * cosSigmaM2
+    val cosSigma: Double = cos(sigma)
+    sinSigma = sin(sigma)
+
+    // eq. 8
+    val phi2: Radians = atan2(
+        sinU1 * cosSigma + cosU1 * sinSigma * cosAlpha1,
+        (1.0 - f) * sqrt(
+            sin2Alpha + (sinU1 * sinSigma - cosU1 * cosSigma * cosAlpha1).pow(2)
+        )
+    ).radians
+
+    // eq. 9
+    // This fixes the pole crossing defect spotted by Matt Feemster. When a
+    // path passes a pole and essentially crosses a line of latitude twice -
+    // once in each direction - the longitude calculation got messed up.
+    //
+    // Using atan2 instead of atan fixes the defect. The change is in the
+    // next 3 lines.
+    //
+    // double tanLambda = sinSigma * sinAlpha1 / (cosU1 * cosSigma - sinU1 *
+    // sinSigma * cosAlpha1);
+    // double lambda = Math.atan(tanLambda);
+    val lambda: Double = atan2(
+        sinSigma * sinAlpha1,
+        cosU1 * cosSigma - sinU1 * sinSigma * cosAlpha1
+    )
+
+    // eq. 10
+    val C = f / 16 * cos2Alpha * (4 + f * (4 - 3 * cos2Alpha))
+
+    // eq. 11
+    val L = lambda - (1 - C) * f * sinAlpha *
+            (sigma.value + C * sinSigma * (cosSigmaM2 + C * cosSigma * (-1 + 2 * cos2SigmaM2)))
+
+    val endPoint = GMC(phi2, L.radians)
+
+    // eq. 12
+
+    return GmcCurve(
+        start,
+        GmcPose(
+            endPoint,
+            atan2(sinAlpha, -sinU1 * sinSigma + cosU1 * cosSigma * cosAlpha1).radians
+        ),
+        distance
+    )
+}
+
+/**
+ * Taken from https://github.com/mgavaghan/geodesy
+ *
+ * Calculate the geodetic curve between two points on a specified reference
+ * ellipsoid. This is the solution to the inverse geodetic problem.
+ *
+ * @receiver reference ellipsoid to use
+ * @param start starting coordinates
+ * @param end ending coordinates
+ * @return solution to the inverse geodetic problem
+ */
+public fun GeoEllipsoid.curveBetween(start: GMC, end: GMC, precision: Double = 1e-6): GmcCurve {
+    //
+    // All equation numbers refer back to Vincenty's publication:
+    // See http://www.ngs.noaa.gov/PUBS_LIB/inverse.pdf
+    //
+
+    // get constants
+    val a = equatorRadius
+    val b = polarRadius
+
+    // get parameters as radians
+    val phi1 = start.latitude
+    val lambda1 = start.longitude
+    val phi2 = end.latitude
+    val lambda2 = end.longitude
+
+    // calculations
+    val a2 = a.kilometers * a.kilometers
+    val b2 = b.kilometers * b.kilometers
+    val a2b2b2 = (a2 - b2) / b2
+    val omega: Radians = lambda2 - lambda1
+    val tanphi1: Double = tan(phi1)
+    val tanU1 = (1.0 - f) * tanphi1
+    val U1: Double = atan(tanU1)
+    val sinU1: Double = sin(U1)
+    val cosU1: Double = cos(U1)
+    val tanphi2: Double = tan(phi2)
+    val tanU2 = (1.0 - f) * tanphi2
+    val U2: Double = atan(tanU2)
+    val sinU2: Double = sin(U2)
+    val cosU2: Double = cos(U2)
+    val sinU1sinU2 = sinU1 * sinU2
+    val cosU1sinU2 = cosU1 * sinU2
+    val sinU1cosU2 = sinU1 * cosU2
+    val cosU1cosU2 = cosU1 * cosU2
+
+    // eq. 13
+    var lambda = omega
+
+    // intermediates we'll need to compute 's'
+    var A = 0.0
+
+    var sigma = 0.0
+    var deltasigma = 0.0
+    var lambda0: Radians
+    var converged = false
+    for (i in 0..19) {
+        lambda0 = lambda
+        val sinlambda: Double = sin(lambda)
+        val coslambda: Double = cos(lambda)
+
+        // eq. 14
+        val sin2sigma =
+            cosU2 * sinlambda * cosU2 * sinlambda + (cosU1sinU2 - sinU1cosU2 * coslambda) * (cosU1sinU2 - sinU1cosU2 * coslambda)
+        val sinsigma: Double = sqrt(sin2sigma)
+
+        // eq. 15
+        val cossigma = sinU1sinU2 + cosU1cosU2 * coslambda
+
+        // eq. 16
+        sigma = atan2(sinsigma, cossigma)
+
+        // eq. 17 Careful! sin2sigma might be almost 0!
+        val sinalpha = if (sin2sigma == 0.0) 0.0 else cosU1cosU2 * sinlambda / sinsigma
+        val alpha: Double = asin(sinalpha)
+        val cosalpha: Double = cos(alpha)
+        val cos2alpha = cosalpha * cosalpha
+
+        // eq. 18 Careful! cos2alpha might be almost 0!
+        val cos2sigmam = if (cos2alpha == 0.0) 0.0 else cossigma - 2 * sinU1sinU2 / cos2alpha
+        val u2 = cos2alpha * a2b2b2
+        val cos2sigmam2 = cos2sigmam * cos2sigmam
+
+        // eq. 3
+        A = 1.0 + u2 / 16384 * (4096 + u2 * (-768 + u2 * (320 - 175 * u2)))
+
+        // eq. 4
+        val B = u2 / 1024 * (256 + u2 * (-128 + u2 * (74 - 47 * u2)))
+
+        // eq. 6
+        deltasigma =
+            B * sinsigma * (cos2sigmam + B / 4 * (cossigma * (-1 + 2 * cos2sigmam2) - B / 6 * cos2sigmam * (-3 + 4 * sin2sigma) * (-3 + 4 * cos2sigmam2)))
+
+        // eq. 10
+        val C = f / 16 * cos2alpha * (4 + f * (4 - 3 * cos2alpha))
+
+        // eq. 11 (modified)
+        lambda = omega + (
+                (1 - C) * f * sinalpha *
+                        (sigma + C * sinsigma * (cos2sigmam + C * cossigma * (-1 + 2 * cos2sigmam2)))
+                ).radians
+
+        // see how much improvement we got
+        val change: Double = abs((lambda - lambda0) / lambda)
+        if (i > 1 && change < precision) {
+            converged = true
+            break
+        }
+    }
+
+    // eq. 19
+    val s: Distance = b * A * (sigma - deltasigma)
+    val alpha1: Radians
+    val alpha2: Radians
+
+    // didn't converge? must be N/S
+    if (!converged) {
+        if (phi1 > phi2) {
+            alpha1 = pi.radians
+            alpha2 = 0.0.radians
+        } else if (phi1 < phi2) {
+            alpha1 = 0.0.radians
+            alpha2 = pi.radians
+        } else {
+            alpha1 = Double.NaN.radians
+            alpha2 = Double.NaN.radians
+        }
+    } else {
+        // eq. 20
+        alpha1 = atan2(
+            cosU2 * sin(lambda),
+            cosU1sinU2 - sinU1cosU2 * cos(lambda)
+        ).radians
+
+        // eq. 21
+        alpha2 = atan2(
+            cosU1 * sin(lambda),
+            -sinU1cosU2 + cosU1sinU2 * cos(lambda)
+        ).radians + pi
+    }
+    return GmcCurve(
+        GmcPose(start, alpha1),
+        GmcPose(end, alpha2),
+        s
+    )
+}

maps-kt-core/src/commonMain/kotlin/center/sciprog/maps/coordinates/GmcPose.kt

@@ -0,0 +1,12 @@
+package center.sciprog.maps.coordinates
+
+/**
+ * A coordinate-bearing pair
+ */
+public data class GmcPose(val coordinates: GeodeticMapCoordinates, val bearing: Angle) {
+    val latitude: Angle get() = coordinates.latitude
+    val longitude: Angle get() = coordinates.longitude
+}
+
+public fun GmcPose.reversed(): GmcPose = copy(bearing = (bearing + Angle.pi).normalized())
+

maps-kt-core/src/commonMain/kotlin/center/sciprog/maps/coordinates/GmcRectangle.kt

@@ -0,0 +1,82 @@
+package center.sciprog.maps.coordinates
+
+/**
+ * A section of the map between two parallels and two meridians. The figure represents a square in a Mercator projection.
+ * Params are two opposing "corners" of  quasi-square.
+ *
+ * Note that this is a rectangle only on a Mercator projection.
+ */
+public data class GmcRectangle(
+    public val a: GeodeticMapCoordinates,
+    public val b: GeodeticMapCoordinates,
+    public val ellipsoid: GeoEllipsoid = GeoEllipsoid.WGS84,
+) {
+    public companion object {
+
+        /**
+         * A quasi-square section. Note that latitudinal distance could be imprecise for large distances
+         */
+        public fun square(
+            center: GeodeticMapCoordinates,
+            width: Distance,
+            height: Distance,
+            ellipsoid: GeoEllipsoid = GeoEllipsoid.WGS84,
+        ): GmcRectangle {
+            val reducedRadius = ellipsoid.reducedRadius(center.latitude)
+            val a = GeodeticMapCoordinates(
+                center.latitude - (height / ellipsoid.polarRadius / 2).radians,
+                center.longitude - (width / reducedRadius / 2).radians
+            )
+            val b = GeodeticMapCoordinates(
+                center.latitude + (height / ellipsoid.polarRadius / 2).radians,
+                center.longitude + (width / reducedRadius / 2).radians
+            )
+            return GmcRectangle(a, b, ellipsoid)
+        }
+    }
+}
+
+public val GmcRectangle.center: GeodeticMapCoordinates
+    get() = GeodeticMapCoordinates(
+        (a.latitude + b.latitude) / 2,
+        (a.longitude + b.longitude) / 2
+    )
+
+/**
+ * Minimum longitude
+ */
+public val GmcRectangle.left: Angle get() = minOf(a.longitude, b.longitude)
+
+/**
+ * maximum longitude
+ */
+public val GmcRectangle.right: Angle get() = maxOf(a.longitude, b.longitude)
+
+/**
+ * Maximum latitude
+ */
+public val GmcRectangle.top: Angle get() = maxOf(a.latitude, b.latitude)
+
+/**
+ * Minimum latitude
+ */
+public val GmcRectangle.bottom: Angle get() = minOf(a.latitude, b.latitude)
+
+public val GmcRectangle.longitudeDelta: Angle get() = abs(a.longitude - b.longitude)
+public val GmcRectangle.latitudeDelta: Angle get() = abs(a.latitude - b.latitude)
+
+public val GmcRectangle.topLeft: GeodeticMapCoordinates get() = GeodeticMapCoordinates(top, left)
+public val GmcRectangle.bottomRight: GeodeticMapCoordinates get() = GeodeticMapCoordinates(bottom, right)
+
+/**
+ * Compute a minimal bounding box including all given boxes. Return null if collection is empty
+ */
+public fun Collection<GmcRectangle>.wrapAll(): GmcRectangle? {
+    if (isEmpty()) return null
+    //TODO optimize computation
+    val minLat = minOf { it.bottom }
+    val maxLat = maxOf { it.top }
+    val minLong = minOf { it.left }
+    val maxLong = maxOf { it.right }
+    return GmcRectangle(GeodeticMapCoordinates(minLat, minLong), GeodeticMapCoordinates(maxLat, maxLong))
+}

maps-kt-core/src/commonMain/kotlin/center/sciprog/maps/coordinates/MapViewPoint.kt

@@ -13,7 +13,7 @@ public data class MapViewPoint(
 }
 
 public fun MapViewPoint.move(delta: GeodeticMapCoordinates): MapViewPoint {
-    val newCoordinates = GeodeticMapCoordinates.ofRadians(
+    val newCoordinates = GeodeticMapCoordinates(
         (focus.latitude + delta.latitude).coerceIn(
             -MercatorProjection.MAXIMUM_LATITUDE,
             MercatorProjection.MAXIMUM_LATITUDE
@@ -30,7 +30,7 @@ public fun MapViewPoint.zoom(
     copy(zoom = (zoom + zoomDelta).coerceIn(2.0, 18.0))
 } else {
     val difScale = (1 - 2.0.pow(-zoomDelta))
-    val newCenter = GeodeticMapCoordinates.ofRadians(
+    val newCenter = GeodeticMapCoordinates(
         focus.latitude + (invariant.latitude - focus.latitude) * difScale,
         focus.longitude + (invariant.longitude - focus.longitude) * difScale
     )

maps-kt-core/src/commonMain/kotlin/center/sciprog/maps/coordinates/MercatorProjection.kt

@@ -5,9 +5,12 @@
 
 package center.sciprog.maps.coordinates
 
-import kotlin.math.*
+import center.sciprog.maps.coordinates.Angle.Companion.pi
+import kotlin.math.atan
+import kotlin.math.ln
+import kotlin.math.sinh
 
-public data class MercatorCoordinates(val x: Double, val y: Double)
+public data class MercatorCoordinates(val x: Distance, val y: Distance)
 
 /**
  * @param baseLongitude the longitude offset in radians
@@ -15,21 +18,21 @@ public data class MercatorCoordinates(val x: Double, val y: Double)
  * @param correctedRadius optional radius correction to account for ellipsoid model
  */
 public open class MercatorProjection(
-    public val baseLongitude: Double = 0.0,
+    public val baseLongitude: Angle = Angle.zero,
-    protected val radius: Double = DEFAULT_EARTH_RADIUS,
+    protected val radius: Distance = DEFAULT_EARTH_RADIUS,
-    private val correctedRadius: ((GeodeticMapCoordinates) -> Double)? = null,
+    private val correctedRadius: ((GeodeticMapCoordinates) -> Distance)? = null,
 ) {
 
     public fun toGeodetic(mc: MercatorCoordinates): GeodeticMapCoordinates {
         val res = GeodeticMapCoordinates.ofRadians(
             atan(sinh(mc.y / radius)),
-            baseLongitude + mc.x / radius,
+            baseLongitude.radians.value + (mc.x / radius),
         )
         return if (correctedRadius != null) {
             val r = correctedRadius.invoke(res)
             GeodeticMapCoordinates.ofRadians(
                 atan(sinh(mc.y / r)),
-                baseLongitude + mc.x / r,
+                baseLongitude.radians.value + mc.x / r,
             )
         } else {
             res
@@ -41,15 +44,15 @@ public open class MercatorProjection(
      */
     public fun toMercator(gmc: GeodeticMapCoordinates): MercatorCoordinates {
         require(abs(gmc.latitude) <= MAXIMUM_LATITUDE) { "Latitude exceeds the maximum latitude for mercator coordinates" }
-        val r = correctedRadius?.invoke(gmc) ?: radius
+        val r: Distance = correctedRadius?.invoke(gmc) ?: radius
         return MercatorCoordinates(
-            x = r * (gmc.longitude - baseLongitude),
+            x = r * (gmc.longitude - baseLongitude).radians.value,
-            y = r * ln(tan(PI / 4 + gmc.latitude / 2))
+            y = r * ln(tan(pi / 4 + gmc.latitude / 2))
         )
     }
 
-    public companion object : MercatorProjection(0.0, 6378137.0) {
+    public companion object : MercatorProjection(Angle.zero, Distance(6378.137)) {
-        public const val MAXIMUM_LATITUDE: Double = 85.05113
+        public val MAXIMUM_LATITUDE: Angle = 85.05113.degrees
-        public val DEFAULT_EARTH_RADIUS: Double = radius
+        public val DEFAULT_EARTH_RADIUS: Distance = radius
     }
 }

maps-kt-core/src/commonMain/kotlin/center/sciprog/maps/coordinates/WebMercatorProjection.kt

@@ -9,7 +9,7 @@ import kotlin.math.*
 
 public data class WebMercatorCoordinates(val zoom: Int, val x: Double, val y: Double)
 
-public object WebMercatorProjection  {
+public object WebMercatorProjection {
 
     /**
      * Compute radians to projection coordinates ratio for given [zoom] factor
@@ -32,8 +32,8 @@ public object WebMercatorProjection  {
         val scaleFactor = scaleFactor(zoom.toDouble())
         return WebMercatorCoordinates(
             zoom = zoom,
-            x = scaleFactor * (gmc.longitude + PI),
+            x = scaleFactor * (gmc.longitude.radians.value + PI),
-            y = scaleFactor * (PI - ln(tan(PI / 4 + gmc.latitude / 2)))
+            y = scaleFactor * (PI - ln(tan(PI / 4 + gmc.latitude.radians.value / 2)))
         )
     }
 

maps-kt-core/src/commonMain/kotlin/center/sciprog/maps/coordinates/angles.kt

@@ -0,0 +1,92 @@
+/*
+ * Copyright 2018-2021 KMath contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package center.sciprog.maps.coordinates
+
+import kotlin.jvm.JvmInline
+import kotlin.math.PI
+
+// Taken from KMath dev version, to be used directly in the future
+
+
+public sealed interface Angle : Comparable<Angle> {
+    public val radians: Radians
+    public val degrees: Degrees
+
+    public operator fun plus(other: Angle): Angle
+    public operator fun minus(other: Angle): Angle
+
+    public operator fun times(other: Number): Angle
+    public operator fun div(other: Number): Angle
+    public operator fun div(other: Angle): Double
+    public operator fun unaryMinus(): Angle
+
+    public companion object {
+        public val zero: Angle = 0.radians
+        public val pi: Angle = PI.radians
+        public val piTimes2: Angle = (2 * PI).radians
+        public val piDiv2: Angle = (PI / 2).radians
+    }
+}
+
+/**
+ * Type safe radians
+ */
+@JvmInline
+public value class Radians(public val value: Double) : Angle {
+    override val radians: Radians
+        get() = this
+    override val degrees: Degrees
+        get() = Degrees(value * 180 / PI)
+
+    public override fun plus(other: Angle): Radians = Radians(value + other.radians.value)
+    public override fun minus(other: Angle): Radians = Radians(value - other.radians.value)
+
+    public override fun times(other: Number): Radians = Radians(value * other.toDouble())
+    public override fun div(other: Number): Radians = Radians(value / other.toDouble())
+    override fun div(other: Angle): Double = value / other.radians.value
+    public override fun unaryMinus(): Radians = Radians(-value)
+
+    override fun compareTo(other: Angle): Int = value.compareTo(other.radians.value)
+}
+
+public fun sin(angle: Angle): Double = kotlin.math.sin(angle.radians.value)
+public fun cos(angle: Angle): Double = kotlin.math.cos(angle.radians.value)
+public fun tan(angle: Angle): Double = kotlin.math.tan(angle.radians.value)
+
+public val Number.radians: Radians get() = Radians(toDouble())
+
+/**
+ * Type safe degrees
+ */
+@JvmInline
+public value class Degrees(public val value: Double) : Angle {
+    override val radians: Radians
+        get() = Radians(value * PI / 180)
+    override val degrees: Degrees
+        get() = this
+
+    public override fun plus(other: Angle): Degrees = Degrees(value + other.degrees.value)
+    public override fun minus(other: Angle): Degrees = Degrees(value - other.degrees.value)
+
+    public override fun times(other: Number): Degrees = Degrees(value * other.toDouble())
+    public override fun div(other: Number): Degrees = Degrees(value / other.toDouble())
+    override fun div(other: Angle): Double = value / other.degrees.value
+    public override fun unaryMinus(): Degrees = Degrees(-value)
+
+    override fun compareTo(other: Angle): Int = value.compareTo(other.degrees.value)
+}
+
+public val Number.degrees: Degrees get() = Degrees(toDouble())
+
+/**
+ * Normalized angle to (0, 2PI) for radians or (0, 360) for degrees.
+ */
+public fun Angle.normalized(): Angle = when (this) {
+    is Degrees -> (value + 180.0).rem(360.0).degrees
+    is Radians -> (value + PI).rem(PI * 2).radians
+}
+
+public fun abs(angle: Angle): Angle = if (angle < Angle.zero) -angle else angle

maps-kt-core/src/commonTest/kotlin/center/sciprog/maps/coordinates/DistanceTest.kt

@@ -0,0 +1,37 @@
+package center.sciprog.maps.coordinates
+
+import kotlin.test.Ignore
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+internal class DistanceTest {
+    companion object {
+        val moscow = GMC.ofDegrees(55.76058287719673, 37.60358622841869)
+        val spb = GMC.ofDegrees(59.926686023580444, 30.36038109122013)
+    }
+
+    @Test
+    fun ellipsoidParameters() {
+        assertEquals(298.257223563, GeoEllipsoid.WGS84.inverseF, 1e-6)
+    }
+
+    @Test
+    @Ignore
+    fun greatCircleDistance() {
+        assertEquals(
+            expected = 632.035,
+            actual = GeoEllipsoid.greatCircleAngleBetween(moscow, spb).value *
+                    GeoEllipsoid.WGS84.equatorRadius.kilometers,
+            absoluteTolerance = 0.1
+        )
+    }
+
+    @Test
+    fun largeDistance() {
+        val curve = GeoEllipsoid.WGS84.curveBetween(moscow, spb)
+        val distance = curve.distance
+
+        assertEquals(632.035426877, distance.kilometers, 0.1)
+
+    }
+}