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add mgrs test for different precisions
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normalize pointcoordinates (there were some issues with longitudes on the dateline)
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@jillesvangurp
jillesvangurp committed Oct 23, 2024
1 parent 7d74ea6 commit 1ccb29a
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Showing 4 changed files with 55 additions and 27 deletions.
22 changes: 7 additions & 15 deletions src/commonMain/kotlin/com/jillesvangurp/geo/mgrs.kt
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Original file line number Diff line number Diff line change
@@ -1,7 +1,6 @@
package com.jillesvangurp.geo

import com.jillesvangurp.geojson.PointCoordinates
import kotlin.math.abs
import kotlin.math.floor

/*
Expand Down Expand Up @@ -30,7 +29,7 @@ import kotlin.math.floor
* MGRS precision for the easting and northing.
* [MgrsCoordinate] stores everything in meter precision but can format with any of these precisions.
*/
enum class MgrsPrecision(val divisor: Int, val digits: Int) {
enum class MgrsPrecision(val meters: Int, val digits: Int) {
TEN_KM(10000,1),
ONE_KM(1000,2),
HUNDRED_M(100,3),
Expand Down Expand Up @@ -64,17 +63,17 @@ data class MgrsCoordinate(
* USNG is the human-readable version of MGRS which includes spaces.
*/
fun usng(precision: MgrsPrecision = MgrsPrecision.ONE_M): String {
val eastingStr = (easting / precision.divisor).toString().padStart(precision.digits, '0')
val northingStr = (northing / precision.divisor).toString().padStart(precision.digits, '0')
val eastingStr = (easting / precision.meters).toString().padStart(precision.digits, '0')
val northingStr = (northing / precision.meters).toString().padStart(precision.digits, '0')
return "$longitudeZone$latitudeZoneLetter $firstLetter$secondLetter $eastingStr $northingStr"
}

/**
* MGRS is the compact format without spaces.
*/
fun mgrs(precision: MgrsPrecision = MgrsPrecision.ONE_M): String {
val eastingStr = (easting / precision.divisor).toString().padStart(precision.digits, '0')
val northingStr = (northing / precision.divisor).toString().padStart(precision.digits, '0')
val eastingStr = (easting / precision.meters).toString().padStart(precision.digits, '0')
val northingStr = (northing / precision.meters).toString().padStart(precision.digits, '0')
return "$longitudeZone$latitudeZoneLetter$firstLetter$secondLetter$eastingStr$northingStr"
}
}
Expand Down Expand Up @@ -248,20 +247,13 @@ fun String.parseMgrs(): MgrsCoordinate? {
} else {
val mid = numbers.length / 2
val precision = MgrsPrecision.entries[mid - 1]
val easting = numbers.substring(0, mid).toInt() * precision.divisor
val northing = numbers.substring(mid).toInt() * precision.divisor
val easting = numbers.substring(0, mid).toInt() * precision.meters
val northing = numbers.substring(mid).toInt() * precision.meters
MgrsCoordinate(longitudeZone, latitudeZoneLetter, firstLetter, secondLetter, easting, northing)
}
}
}

private fun roundMGRS(value: Double): Long {
val ival = floor(value).toLong()
val fraction = value - ival
// double fraction = modf (value, &ivalue);
return if (fraction > 0.5 || fraction == 0.5 && ival % 2L == 1L) ival + 1 else ival
}

data class UpsConstant(
val latitudeZoneLetter: Char,
val chars: List<Char>,
Expand Down
29 changes: 19 additions & 10 deletions src/commonMain/kotlin/com/jillesvangurp/geo/utm.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@ import com.jillesvangurp.geo.GeoGeometry.Companion.toRadians
import com.jillesvangurp.geojson.PointCoordinates
import com.jillesvangurp.geojson.latitude
import com.jillesvangurp.geojson.longitude
import com.jillesvangurp.geojson.normalize
import kotlin.math.*

/**
Expand Down Expand Up @@ -110,7 +111,7 @@ data class UtmCoordinate(
}
}

val UtmCoordinate.isUps get() = latitudeZoneLetter in listOf('A','B', 'Y', 'Z')
val UtmCoordinate.isUps get() = latitudeZoneLetter in listOf('A', 'B', 'Y', 'Z')
val UtmCoordinate.isUtm get() = !isUps

val UtmCoordinate.isSouth get() = latitudeZoneLetter < 'N'
Expand Down Expand Up @@ -218,7 +219,7 @@ private fun getLongitudeZone(latLong: PointCoordinates): Int {
// UPS longitude zones
val longitude = latLong.longitude
return if (isNorthPolar(latLong) || isSouthPolar(latLong)) {
if (longitude < 0.0) {
if (longitude < 0.0) {
30
} else {
31
Expand All @@ -227,30 +228,35 @@ private fun getLongitudeZone(latLong: PointCoordinates): Int {
val latitudeZone: Char = getLatitudeZoneLetter(latLong)
when {
latitudeZone == 'X' && longitude > 0.0 && longitude < 42.0 -> {
// X latitude exceptions
// X latitude exceptions
when {
longitude < 9.0 -> {
31
}

longitude < 21.0 -> {
33
}

longitude < 33.0 -> {
35
}

else -> {
37
}
}
}

latitudeZone == 'V' && longitude > 0.0 && longitude < 12.0 -> {
// V latitude exceptions
// V latitude exceptions
if (longitude < 3.0) {
31
} else {
32
}
}

else -> {
((longitude + 180) / 6).toInt() + 1
}
Expand Down Expand Up @@ -293,16 +299,16 @@ private fun getCentralMeridian(longitudeZone: Int, latitudeZone: Char): Double {
/**
* Converts to UTM or UPS and selects the coordinate system based on the latitude.
*/
fun PointCoordinates.toUtmOrUps() : UtmCoordinate {
fun PointCoordinates.toUtmOrUps(): UtmCoordinate {
return if (latitude < UTM_SOUTHERN_LIMIT || latitude > UTM_NORTHERN_LIMIT) {
toUpsCoordinate()
} else {
toUtmCoordinate()
}
}

fun UtmCoordinate.toPointCoordinates() : PointCoordinates {
return if(isUps) upsToPointCoordinates() else utmToPointCoordinates()
fun UtmCoordinate.toPointCoordinates(): PointCoordinates {
return if (isUps) upsToPointCoordinates() else utmToPointCoordinates()
}

fun PointCoordinates.toUtmCoordinate(): UtmCoordinate {
Expand Down Expand Up @@ -472,7 +478,10 @@ fun UtmCoordinate.utmToPointCoordinates(): PointCoordinates {
* (61.0 + 662.0 * tan2Phi + 1320.0 * tan4Phi + 720.0 * tan6Phi))
val latitude = phi - dE2 * t10 + dE4 * t11 - dE6 * t12 + dE8 * t13
val longitude = (lambda0 + dE * t14 - dE3 * t15 + dE5 * t16 - dE7 * t17)
return doubleArrayOf(fromRadians(longitude), fromRadians(latitude))
return doubleArrayOf(
fromRadians(longitude),
fromRadians(latitude)
).normalize()
}

/**
Expand All @@ -487,7 +496,7 @@ fun UtmCoordinate.utmToPointCoordinates(): PointCoordinates {
* - I've found and fixed several bugs in the UTM implementation where I did have access to those
*/
fun PointCoordinates.toUpsCoordinate(): UtmCoordinate {
if (latitude >= UTM_SOUTHERN_LIMIT && latitude <= UTM_NORTHERN_LIMIT) {
if (latitude in UTM_SOUTHERN_LIMIT..UTM_NORTHERN_LIMIT) {
error("$latitude is outside UPS supported latitude range of [-90 - $UTM_SOUTHERN_LIMIT] or [$UTM_NORTHERN_LIMIT - 90]. You should use UTM")
}

Expand Down Expand Up @@ -572,7 +581,7 @@ fun UtmCoordinate.upsToPointCoordinates(): PointCoordinates {
} else {
-phi
}
return doubleArrayOf(fromRadians(longitude), fromRadians(latitude))
return doubleArrayOf(fromRadians(longitude), fromRadians(latitude)).normalize()
}


Expand Down
23 changes: 23 additions & 0 deletions src/commonMain/kotlin/com/jillesvangurp/geojson/geojson.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -79,6 +79,29 @@ val PointCoordinates.longitude: Double
get() = this[0]
val PointCoordinates.x get() = longitude

fun PointCoordinates.normalize(): PointCoordinates {
return if (longitude < -180.0 || longitude > 180.0 || latitude < -90.0 || latitude > 90.0) {
doubleArrayOf(
// Longitude normalization
((longitude + 180.0) % 360.0 + 360.0) % 360.0 - 180.0,
// Latitude normalization with modulo to account for multiple rotations (edge case)
when (val lat = ((latitude + 90.0) % 360.0 + 360.0) % 360.0 - 90.0) {
in 90.0..180.0 -> {
180.0 - lat
}
in -180.0..-90.0 -> {
-180.0 - lat
}
else -> {
lat
}
}
)
} else {
this
}
}

enum class CompassDirection(val letter: Char) { East('E'), West('W'), South('S'), North('N') }

typealias Degree = Double
Expand Down
8 changes: 6 additions & 2 deletions src/commonTest/kotlin/com/jillesvangurp/geogeometry/UTMTest.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -166,10 +166,14 @@ class UTMTest {
convertedBack.distanceTo(p) shouldBeLessThan 1.0
}
}

val toMgrs = toUTM.toMgrs()
withClue("${p.latitude},${p.longitude} $toMgrs") {
toMgrs.toString().parseMgrs()!!.toPointCoordinate().distanceTo(p) shouldBeLessThan 2.0
MgrsPrecision.entries.forEach {precision ->
withClue(precision) {
toMgrs.usng(precision).parseMgrs()!!.toPointCoordinate().distanceTo(p) shouldBeLessThan 2.0 * precision.meters
}
}
}

val newUtm = toMgrs.toUtm()
Expand Down

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