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add: TPoint_MakeCoords: create a sequence of coordinates based on arrays of coordinates
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‎src/main/java/examples/N15_TPoint_MakeCoords.java‎

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package examples;
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import jnr.ffi.Pointer;
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import jnr.ffi.Memory;
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import jnr.ffi.Runtime;
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import types.temporal.TInterpolation;
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import java.time.OffsetDateTime;
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import static functions.functions.*;
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/**
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* Demonstrates creating temporal point sequences from coordinate arrays.
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*
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* Alternative Construction Method:
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* Instead of creating TPoint from individual instants, this approach uses
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* arrays of coordinates (x[], y[], z[], timestamps[]) to build sequences directly.
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*
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* This could be useful when data comes from:
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* - GPS logs (CSV with separate x, y, time columns)
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* - Sensor arrays (parallel data streams)
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* - Scientific instruments (time-series measurements)
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*
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* The program demonstrates three variants:
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* 1. 3D Point (x, y, z) - Projected coordinates (SRID 5676 - UTM 46N)
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* 2. 2D Point (x, y) - Projected coordinates (SRID 5676)
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* 3. 2D Point (x, y) - Geographic coordinates (SRID 4326 - WGS84)
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*
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* Function: tpointseq_make_coords(x[], y[], z[], times[], count, srid, ...)
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*/
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public class N15_TPoint_MakeCoords {
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// PostgreSQL epoch: 2000-01-01 00:00:00 UTC
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private static final long POSTGRES_EPOCH_MICROSECONDS = 946684800000000L;
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/**
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* Parse timestamp string to Unix timestamp (seconds since 1970-01-01)
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*
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* tpointseq_make_coords() expects Unix timestamps in seconds
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*/
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private static long parseTimestamp(String timeStr) {
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// Parse string to OffsetDateTime
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OffsetDateTime odt = pg_timestamptz_in(timeStr, -1);
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// Convert to Java Instant
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java.time.Instant instant = odt.toInstant();
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// Return Unix epoch SECONDS (not microseconds, no PostgreSQL epoch adjustment)
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return instant.getEpochSecond();
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}
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/**
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* SECTION 1: 3D Point Sequence (Projected Coordinates)
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* Creates a 3D temporal point sequence with elevation (z coordinate)
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*/
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private static void demonstrate3DProjected() {
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System.out.println("\n" + "=".repeat(60));
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System.out.println("SECTION 1: 3D Point Sequence (Projected - UTM 46N)");
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System.out.println("=".repeat(60));
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// Coordinate arrays (UTM coordinates in meters)
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double[] xcoords = {691875.63, 691876.45, 691875.82, 691876.91};
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double[] ycoords = {6176943.21, 6176944.65, 6176943.54, 6176944.98};
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double[] zcoords = {10.5, 12.3, 11.8, 13.2}; // Elevation in meters
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// Time array
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String[] timeStrs = {
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"2000-01-01 00:00:00",
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"2000-01-02 00:00:00",
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"2000-01-03 00:00:00",
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"2000-01-04 00:00:00"
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};
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int count = 4;
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System.out.println("\nInput Data:");
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System.out.println("┌─ COORDINATE ARRAYS ──────────────────────");
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for (int i = 0; i < count; i++) {
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System.out.printf("│ Point %d: x=%.2f, y=%.2f, z=%.2f @ %s\n",
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i + 1, xcoords[i], ycoords[i], zcoords[i], timeStrs[i]);
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}
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System.out.println("└──────────────────────────────────────────");
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Runtime runtime = Runtime.getSystemRuntime();
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// Allocate native memory for coordinate arrays
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Pointer xPtr = Memory.allocate(runtime, Double.BYTES * count);
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Pointer yPtr = Memory.allocate(runtime, Double.BYTES * count);
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Pointer zPtr = Memory.allocate(runtime, Double.BYTES * count);
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// Copy Java arrays to native memory
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for (int i = 0; i < count; i++) {
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xPtr.putDouble(i * Double.BYTES, xcoords[i]);
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yPtr.putDouble(i * Double.BYTES, ycoords[i]);
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zPtr.putDouble(i * Double.BYTES, zcoords[i]);
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}
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// Allocate native memory for timestamps array
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Pointer timesPtr = Memory.allocate(runtime, Long.BYTES * count);
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// Convert and store timestamps
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for (int i = 0; i < count; i++) {
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long timestamp = parseTimestamp(timeStrs[i]);
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timesPtr.putLong(i * Long.BYTES, timestamp);
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}
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// Create 3D sequence from coordinate arrays
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Pointer seq = tpointseq_make_coords(
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xPtr, // Pointer to X coordinates
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yPtr, // Pointer to Y coordinates
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zPtr, // Pointer to Z coordinates (elevation)
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timesPtr, // Pointer to timestamps
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count, // Number of points
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5676, // SRID (UTM Zone 46N)
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false, // Not geodetic (projected)
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true, // Lower bound inclusive
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true, // Upper bound inclusive
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TInterpolation.LINEAR.getValue(), // Interpolation: 1 = Linear
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true // Normalize
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);
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// Output as EWKT
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String ewkt = tspatial_as_ewkt(seq, 2);
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System.out.println("\n┌─ RESULT (3D SEQUENCE) ───────────────────");
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System.out.println("│ EWKT:");
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System.out.println("│ " + ewkt);
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System.out.println("│");
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System.out.println("│ Interpretation:");
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System.out.println("│ - SRID 5676 = UTM Zone 46N (projected)");
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System.out.println("│ - 3D points with elevation (Z coordinate)");
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System.out.println("│ - Linear interpolation between points");
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System.out.println("└──────────────────────────────────────────");
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}
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/**
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* SECTION 2: 2D Point Sequence (Projected Coordinates)
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* Creates a 2D temporal point sequence without elevation
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*/
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private static void demonstrate2DProjected() {
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System.out.println("\n" + "=".repeat(60));
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System.out.println("SECTION 2: 2D Point Sequence (Projected - UTM 46N)");
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System.out.println("=".repeat(60));
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// Coordinate arrays (same as 3D, but no Z)
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double[] xcoords = {691875.63, 691876.45, 691875.82, 691876.91};
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double[] ycoords = {6176943.21, 6176944.65, 6176943.54, 6176944.98};
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// Time array
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String[] timeStrs = {
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"2000-01-01 00:00:00",
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"2000-01-02 00:00:00",
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"2000-01-03 00:00:00",
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"2000-01-04 00:00:00"
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};
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int count = 4;
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System.out.println("\nInput Data:");
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System.out.println("┌─ COORDINATE ARRAYS ──────────────────────");
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for (int i = 0; i < count; i++) {
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System.out.printf("│ Point %d: x=%.2f, y=%.2f @ %s\n",
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i + 1, xcoords[i], ycoords[i], timeStrs[i]);
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}
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System.out.println("└──────────────────────────────────────────");
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Runtime runtime = Runtime.getSystemRuntime();
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// Allocate native memory for coordinate arrays
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Pointer xPtr = Memory.allocate(runtime, Double.BYTES * count);
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Pointer yPtr = Memory.allocate(runtime, Double.BYTES * count);
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// Copy Java arrays to native memory
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for (int i = 0; i < count; i++) {
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xPtr.putDouble(i * Double.BYTES, xcoords[i]);
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yPtr.putDouble(i * Double.BYTES, ycoords[i]);
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}
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// Allocate native memory for timestamps array
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Pointer timesPtr = Memory.allocate(runtime, Long.BYTES * count);
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// Convert and store timestamps
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for (int i = 0; i < count; i++) {
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long timestamp = parseTimestamp(timeStrs[i]);
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timesPtr.putLong(i * Long.BYTES, timestamp);
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}
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// Create 2D sequence from coordinate arrays
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// Pass null for zPtr to create 2D points
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Pointer seq = tpointseq_make_coords(
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xPtr, // Pointer to X coordinates
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yPtr, // Pointer to Y coordinates
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null, // No Z coordinates (2D)
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timesPtr, // Pointer to timestamps
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count, // Number of points
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5676, // SRID (UTM Zone 46N)
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false, // Not geodetic (projected)
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true, // Lower bound inclusive
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true, // Upper bound inclusive
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TInterpolation.LINEAR.getValue(), // Interpolation: 1 = Linear
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true // Normalize
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);
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// Output as EWKT
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String ewkt = tspatial_as_ewkt(seq, 2);
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System.out.println("\n┌─ RESULT (2D SEQUENCE) ───────────────────");
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System.out.println("│ EWKT:");
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System.out.println("│ " + ewkt);
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System.out.println("│");
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System.out.println("│ Interpretation:");
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System.out.println("│ - SRID 5676 = UTM Zone 46N (projected)");
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System.out.println("│ - 2D points (no elevation)");
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System.out.println("│ - Same coordinates as 3D, but Z omitted");
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System.out.println("└──────────────────────────────────────────");
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}
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/**
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* SECTION 3: 2D Point Sequence (Geographic Coordinates)
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* Creates a geographic temporal point sequence (latitude/longitude)
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*/
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private static void demonstrate2DGeographic() {
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System.out.println("\n" + "=".repeat(60));
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System.out.println("SECTION 3: 2D Point Sequence (Geographic - WGS84)");
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System.out.println("=".repeat(60));
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// Geographic coordinates (longitude, latitude)
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double[] xcoords = {2.349014, 2.349156, 2.349089, 2.349201}; // Longitude
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double[] ycoords = {48.852968, 48.853142, 48.853034, 48.853215}; // Latitude
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// Time array
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String[] timeStrs = {
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"2000-01-01 00:00:00",
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"2000-01-02 00:00:00",
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"2000-01-03 00:00:00",
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"2000-01-04 00:00:00"
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};
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int count = 4;
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System.out.println("\nInput Data (Paris, France):");
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System.out.println("┌─ COORDINATE ARRAYS ──────────────────────");
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for (int i = 0; i < count; i++) {
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System.out.printf("│ Point %d: lon=%.6f, lat=%.6f @ %s\n",
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i + 1, xcoords[i], ycoords[i], timeStrs[i]);
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}
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System.out.println("└──────────────────────────────────────────");
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Runtime runtime = Runtime.getSystemRuntime();
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// Allocate native memory for coordinate arrays
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Pointer xPtr = Memory.allocate(runtime, Double.BYTES * count);
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Pointer yPtr = Memory.allocate(runtime, Double.BYTES * count);
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// Copy Java arrays to native memory
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for (int i = 0; i < count; i++) {
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xPtr.putDouble(i * Double.BYTES, xcoords[i]);
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yPtr.putDouble(i * Double.BYTES, ycoords[i]);
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}
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// Allocate native memory for timestamps array
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Pointer timesPtr = Memory.allocate(runtime, Long.BYTES * count);
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// Convert and store timestamps
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for (int i = 0; i < count; i++) {
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long timestamp = parseTimestamp(timeStrs[i]);
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timesPtr.putLong(i * Long.BYTES, timestamp);
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}
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// Create geographic sequence from coordinate arrays
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Pointer seq = tpointseq_make_coords(
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xPtr, // Longitude
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yPtr, // Latitude
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null, // No Z coordinates
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timesPtr, // Pointer to timestamps
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count, // Number of points
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4326, // SRID (WGS84 - standard GPS coordinates)
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true, // Geodetic (geographic)
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true, // Lower bound inclusive
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true, // Upper bound inclusive
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TInterpolation.LINEAR.getValue(), // Interpolation: 1 = Linear
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true // Normalize
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);
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// Output as EWKT
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String ewkt = tspatial_as_ewkt(seq, 6); // 6 decimals for geographic
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System.out.println("\n┌─ RESULT (GEOGRAPHIC SEQUENCE) ───────────");
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System.out.println("│ EWKT:");
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System.out.println("│ " + ewkt);
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System.out.println("│");
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System.out.println("│ Interpretation:");
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System.out.println("│ - SRID 4326 = WGS84 (standard GPS)");
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System.out.println("│ - Geographic coordinates (lon/lat)");
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System.out.println("│ - Geodetic = true (distances on sphere)");
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System.out.println("│ - Location: Near Eiffel Tower, Paris");
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System.out.println("└──────────────────────────────────────────");
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}
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/**
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* Explain the coordinate arrays approach
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*/
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private static void explainCoordinateArrays() {
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System.out.println("\n╔═══════════════════════════════════════════════════════════╗");
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System.out.println("║ COORDINATE ARRAYS CONSTRUCTION EXPLAINED ║");
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System.out.println("╚═══════════════════════════════════════════════════════════╝");
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System.out.println();
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System.out.println("Two Ways to Create Temporal Point Sequences:");
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System.out.println("───────────────────────────────────────────");
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System.out.println();
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System.out.println("┌─ METHOD 1: From Instants (Traditional) ──────────────────");
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System.out.println("│");
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System.out.println("│ TInstant inst1 = new TInstant(\"POINT(1 2)@2000-01-01\");");
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System.out.println("│ TInstant inst2 = new TInstant(\"POINT(2 3)@2000-01-02\");");
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System.out.println("│ TInstant inst3 = new TInstant(\"POINT(3 4)@2000-01-03\");");
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System.out.println("│");
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System.out.println("│ TSequence seq = new TSequence(instants, 3, ...);");
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System.out.println("│");
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System.out.println("│ Use when: Data comes as complete WKT strings");
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System.out.println("│");
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System.out.println("└──────────────────────────────────────────────────────────");
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System.out.println();
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System.out.println("┌─ METHOD 2: From Coordinate Arrays (This Program) ────────");
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System.out.println("│");
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System.out.println("│ // Java arrays");
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System.out.println("│ double[] x = {1, 2, 3};");
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System.out.println("│ double[] y = {2, 3, 4};");
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System.out.println("│");
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System.out.println("│ // Allocate native memory and copy");
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System.out.println("│ Pointer xPtr = Memory.allocate(runtime, Double.BYTES * 3);");
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System.out.println("│ for (int i = 0; i < 3; i++)");
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System.out.println("│ xPtr.putDouble(i * Double.BYTES, x[i]);");
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System.out.println("│");
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System.out.println("│ // Same for y and timestamps...");
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System.out.println("│");
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System.out.println("│ Pointer seq = tpointseq_make_coords(xPtr, yPtr, null,");
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System.out.println("│ timesPtr, 3, ...);");
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System.out.println("│");
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System.out.println("│ Use when: Data comes as separate coordinate columns");
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System.out.println("│");
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System.out.println("└──────────────────────────────────────────────────────────");
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System.out.println();
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System.out.println("When to Use Coordinate Arrays:");
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System.out.println("──────────────────────────────");
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System.out.println("✓ Sensor data: Separate streams for each dimension");
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System.out.println("✓ Database exports: Tabular format");
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System.out.println();
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System.out.println("Example CSV Data:");
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System.out.println("────────────────");
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System.out.println("timestamp,longitude,latitude,elevation");
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System.out.println("2000-01-01 00:00:00,2.349,48.853,10.5");
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System.out.println("2000-01-02 00:00:00,2.350,48.854,12.3");
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System.out.println("2000-01-03 00:00:00,2.351,48.855,11.8");
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System.out.println();
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System.out.println("→ Perfect for tpointseq_make_coords()!");
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System.out.println();
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System.out.println();
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}
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public static void main(String[] args) {
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// Initialize MEOS
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meos_initialize();
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meos_initialize_timezone("UTC");
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try {
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System.out.println("\n" + "=".repeat(60));
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System.out.println("Temporal Point Construction from Coordinate Arrays");
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System.out.println("=".repeat(60));
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// Explain the approach
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explainCoordinateArrays();
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// Run all demonstrations
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demonstrate3DProjected();
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demonstrate2DProjected();
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demonstrate2DGeographic();
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System.out.println("\n" + "=".repeat(60));
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System.out.println("DEMONSTRATION COMPLETED!");
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System.out.println("=".repeat(60));
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System.out.println();
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System.out.println("Key Takeaways:");
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System.out.println("──────────────");
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System.out.println("1. Use coordinate arrays when data is in tabular format");
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System.out.println("2. 3D points include elevation (z coordinate)");
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System.out.println("3. Geographic (4326) vs Projected (5676) coordinates");
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System.out.println("4. More efficient than creating individual instants");
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System.out.println();
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} catch (Exception e) {
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System.err.println("Error: " + e.getMessage());
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e.printStackTrace();
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} finally {
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// Finalize MEOS
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meos_finalize();
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}
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}
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}

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