Verify and document FRFcoord multiple point input support

VERIFICATION_FRF_MULTIPLE_POINTS.md

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+# FRFcoord Multiple Point Input Support - Verification
+
+## Issue Summary
+
+**Original Issue**: "Currently `FRFcoord` is limited to single point inputs thereby requiring looping outside of this function."
+
+**Agent Instructions**: "I think this was solved with most recent update to Transformer class in pyproj. confirm or fix"
+
+## Verification Results
+
+### ✅ CONFIRMED: `FRFcoord` Already Supports Multiple Input Points
+
+The `FRFcoord` function and all related coordinate transformation functions in `murgtools.utils.geoprocess` **already support multiple input points** without requiring any code changes.
+
+This functionality is enabled by pyproj version 3.0+, which provides native array handling in the `Transformer` class.
+
+## Key Findings
+
+### Supported Input Types
+
+1. **Single Point** (original functionality)
+   - Input: `FRFcoord(566.93, 515.11)`
+   - Output: Scalar/float values
+
+2. **NumPy Arrays** (enhanced functionality)
+   - Input: `FRFcoord(np.array([100, 200, 300]), np.array([100, 200, 300]))`
+   - Output: NumPy arrays of same shape
+
+3. **Python Lists** (automatic conversion)
+   - Input: `FRFcoord([100, 200, 300], [100, 200, 300])`
+   - Output: NumPy arrays (lists automatically converted)
+
+### Supported Coordinate Systems
+
+All coordinate systems support array inputs:
+- **FRF Local Coordinates** (xFRF, yFRF)
+- **NC State Plane** (EPSG:3358)
+- **Lat/Lon** (WGS84, EPSG:4326)
+- **UTM** (Zone 18S)
+
+### Functions Supporting Arrays
+
+All transformation functions support array inputs:
+- `FRFcoord(p1, p2, coordType)` - Universal converter
+- `FRF2ncsp(xFRF, yFRF)` - FRF to State Plane
+- `ncsp2FRF(spE, spN)` - State Plane to FRF
+- `ncsp2LatLon(spE, spN)` - State Plane to Lat/Lon
+- `LatLon2ncsp(lon, lat)` - Lat/Lon to State Plane
+- `LatLon2utm(lat, lon)` - Lat/Lon to UTM
+- `utm2LatLon(utmE, utmN, zn, zl)` - UTM to Lat/Lon
+- `utm2ncsp(utmE, utmN, zn, zl)` - UTM to State Plane
+- `ncsp2utm(easting, northing)` - State Plane to UTM
+
+## Usage Examples
+
+### Example 1: Converting Multiple FRF Points
+
+```python
+import numpy as np
+from murgtools.utils import geoprocess as gp
+
+# Define multiple points in FRF coordinates
+x_frf = np.array([100.0, 200.0, 300.0, 566.93])
+y_frf = np.array([100.0, 200.0, 300.0, 515.11])
+
+# Convert all points at once (no loop needed!)
+result = gp.FRFcoord(x_frf, y_frf)
+
+# Access converted coordinates
+print(f"State Plane Easting: {result['StateplaneE']}")
+print(f"State Plane Northing: {result['StateplaneN']}")
+print(f"Latitude: {result['Lat']}")
+print(f"Longitude: {result['Lon']}")
+print(f"UTM Easting: {result['utmE']}")
+print(f"UTM Northing: {result['utmN']}")
+```
+
+### Example 2: Converting Multiple Lat/Lon Points
+
+```python
+import numpy as np
+from murgtools.utils import geoprocess as gp
+
+# Define multiple points in Lat/Lon
+lon = np.array([-75.75, -75.74, -75.73])
+lat = np.array([36.17, 36.18, 36.19])
+
+# Convert all at once
+result = gp.FRFcoord(lon, lat)
+
+# Get FRF coordinates for all points
+xFRF = result['xFRF']
+yFRF = result['yFRF']
+```
+
+### Example 3: Using Lists Instead of Arrays
+
+```python
+from murgtools.utils import geoprocess as gp
+
+# Python lists work too!
+x_list = [100.0, 200.0, 300.0]
+y_list = [100.0, 200.0, 300.0]
+
+result = gp.FRFcoord(x_list, y_list)
+# Output is automatically converted to numpy arrays
+```
+
+## Test Results
+
+All 32 existing tests pass, including:
+- Single point conversions
+- Array conversions
+- List conversions
+- Round-trip conversions (FRF → SP → LL → SP → FRF)
+- All coordinate system combinations
+
+```bash
+pytest tests/test_geoprocess.py -v
+# Result: 32 passed, 1 warning in 1.57s
+```
+
+## Technical Details
+
+### How It Works
+
+1. **pyproj Transformer**: Version 3.0+ of pyproj includes native support for array transformations
+2. **FRFcoord Logic**: The function automatically detects array inputs using `np.size(p1) > 1`
+3. **Consistent Behavior**: Uses `.all()` for array comparisons when detecting coordinate types
+4. **Pass-through**: Arrays are passed through all transformation functions without modification
+
+### Implementation in Code
+
+The key code in `FRFcoord` (lines 321-344 of geoprocess.py):
+
+```python
+# convert list to array if needed
+if isinstance(p1, list):
+    p1 = np.asarray(p1)
+if isinstance(p2, list):
+    p2 = np.asarray(p2)
+
+# now run checks to see what version of input we have!
+if np.size(p1) > 1:
+    LL1 = (np.floor(np.absolute(p1)) == 75).all()
+    LL2 = (np.floor(p2) == 36).all()
+    SP1 = (p1 > 800000).all()
+    SP2 = (p2 > 200000).all()
+    # ... etc
+```
+
+The pyproj Transformer handles arrays natively (lines 195-200):
+
+```python
+transformer = pyproj.Transformer.from_crs(
+    f"epsg:{EPSG}",
+    "epsg:4326",
+    always_xy=True
+)
+lon, lat = transformer.transform(spE, spN)  # Works with arrays!
+```
+
+## Conclusion
+
+✅ **No code changes required** - the functionality already exists and is fully tested.
+
+The issue has been resolved by the update to pyproj 3.0+, which provides native array handling in the `Transformer` class. The `FRFcoord` function and all related coordinate transformation functions properly leverage this capability.
+
+Users can now convert multiple points without external loops, significantly improving performance and code simplicity.
+
+## Dependencies
+
+- **pyproj >= 3.0.0** (current: 3.7.2)
+- **numpy >= 1.20.1**
+
+These are already specified in `requirements.txt`.

examples/demo_multiple_point_conversion.py

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+#!/usr/bin/env python3
+"""
+Demo: FRFcoord Multiple Point Input Support
+
+This example demonstrates that FRFcoord and related coordinate transformation
+functions in murgtools already support multiple input points without requiring
+external loops.
+
+This capability is provided by pyproj >= 3.0.0, which has native array support
+in the Transformer class.
+"""
+
+import numpy as np
+from murgtools.utils import geoprocess as gp
+
+
+def demo_single_point():
+    """Demonstrate single point conversion (original functionality)."""
+    print("=" * 70)
+    print("DEMO 1: Single Point Conversion")
+    print("=" * 70)
+
+    # Single point in FRF coordinates
+    x = 566.93
+    y = 515.11
+
+    print(f"\nInput: FRF coordinates")
+    print(f"  xFRF = {x} m")
+    print(f"  yFRF = {y} m")
+
+    result = gp.FRFcoord(x, y)
+
+    print(f"\nOutput: All coordinate systems")
+    print(f"  State Plane E: {result['StateplaneE']:.2f} m")
+    print(f"  State Plane N: {result['StateplaneN']:.2f} m")
+    print(f"  Latitude:      {result['Lat']:.6f}°")
+    print(f"  Longitude:     {result['Lon']:.6f}°")
+    if isinstance(result['utmE'], np.ndarray):
+        print(f"  UTM E:         {result['utmE'][0]:.2f} m")
+        print(f"  UTM N:         {result['utmN'][0]:.2f} m")
+    else:
+        print(f"  UTM E:         {result['utmE']:.2f} m")
+        print(f"  UTM N:         {result['utmN']:.2f} m")
+    print()
+
+
+def demo_array_input():
+    """Demonstrate array input conversion (enhanced functionality)."""
+    print("=" * 70)
+    print("DEMO 2: Multiple Points - Array Input (No Loop Needed!)")
+    print("=" * 70)
+
+    # Multiple points in FRF coordinates
+    x_array = np.array([0.0, 100.0, 200.0, 300.0, 566.93])
+    y_array = np.array([0.0, 100.0, 200.0, 300.0, 515.11])
+
+    print(f"\nInput: {len(x_array)} points as numpy arrays")
+    print(f"  xFRF = {x_array}")
+    print(f"  yFRF = {y_array}")
+
+    result = gp.FRFcoord(x_array, y_array)
+
+    print(f"\nOutput: All {len(x_array)} points converted simultaneously")
+    print(f"  State Plane E: {result['StateplaneE']}")
+    print(f"  Latitude:      {result['Lat']}")
+    print()
+    print(f"Result types: {type(result['xFRF'])} with shape {result['xFRF'].shape}")
+    print()
+
+
+def demo_different_coordinate_systems():
+    """Demonstrate array conversion for different input coordinate systems."""
+    print("=" * 70)
+    print("DEMO 3: Different Input Coordinate Systems (All Support Arrays)")
+    print("=" * 70)
+
+    # Test with Lat/Lon
+    print("\n3a. Lat/Lon Input:")
+    lon = np.array([-75.75, -75.74, -75.73])
+    lat = np.array([36.17, 36.18, 36.19])
+    result = gp.FRFcoord(lon, lat)
+    print(f"  Input:  {len(lon)} Lat/Lon points")
+    print(f"  Output: xFRF = {result['xFRF'][:3]}")
+
+    # Test with State Plane
+    print("\n3b. State Plane Input:")
+    sp_e = np.array([902000.0, 902100.0, 902200.0])
+    sp_n = np.array([274000.0, 274100.0, 274200.0])
+    result = gp.FRFcoord(sp_e, sp_n)
+    print(f"  Input:  {len(sp_e)} State Plane points")
+    print(f"  Output: xFRF = {result['xFRF']}")
+
+    # Test with Lists (automatically converted)
+    print("\n3c. Python List Input (auto-converted to arrays):")
+    x_list = [100.0, 200.0, 300.0]
+    y_list = [100.0, 200.0, 300.0]
+    result = gp.FRFcoord(x_list, y_list)
+    print(f"  Input:  {len(x_list)} points as Python lists")
+    print(f"  Output: {type(result['xFRF'])} with values {result['xFRF']}")
+    print()
+
+
+def demo_individual_functions():
+    """Demonstrate that individual transformation functions also support arrays."""
+    print("=" * 70)
+    print("DEMO 4: Individual Transformation Functions (All Support Arrays)")
+    print("=" * 70)
+
+    # Test FRF2ncsp
+    print("\n4a. FRF2ncsp (FRF to State Plane):")
+    x = np.array([100.0, 200.0, 300.0])
+    y = np.array([100.0, 200.0, 300.0])
+    result = gp.FRF2ncsp(x, y)
+    print(f"  Input:  {len(x)} FRF points")
+    print(f"  Output: StateplaneE = {result['StateplaneE']}")
+
+    # Test ncsp2LatLon
+    print("\n4b. ncsp2LatLon (State Plane to Lat/Lon):")
+    result = gp.ncsp2LatLon(result['StateplaneE'], result['StateplaneN'])
+    print(f"  Output: Latitude = {result['lat']}")
+
+    # Test LatLon2ncsp
+    print("\n4c. LatLon2ncsp (Lat/Lon to State Plane):")
+    result2 = gp.LatLon2ncsp(result['lon'], result['lat'])
+    print(f"  Output: StateplaneE = {result2['StateplaneE']}")
+
+    print("\n✓ Round-trip conversion successful!")
+    print()
+
+
+def demo_performance_comparison():
+    """Compare performance between loop and array approaches."""
+    print("=" * 70)
+    print("DEMO 5: Performance Comparison")
+    print("=" * 70)
+
+    import time
+
+    # Create test data
+    n = 100
+    x = np.linspace(0, 1000, n)
+    y = np.linspace(0, 1000, n)
+
+    print(f"\nConverting {n} points...")
+
+    # Method 1: Loop (old way)
+    print("\nMethod 1: Loop (OLD - not necessary)")
+    start = time.time()
+    results = []
+    for i in range(n):
+        results.append(gp.FRFcoord(x[i], y[i]))
+    time_loop = time.time() - start
+    print(f"  Time: {time_loop:.4f} seconds")
+
+    # Method 2: Array (new way)
+    print("\nMethod 2: Array (NEW - already supported!)")
+    start = time.time()
+    result = gp.FRFcoord(x, y)
+    time_array = time.time() - start
+    print(f"  Time: {time_array:.4f} seconds")
+
+    # Compare
+    speedup = time_loop / time_array
+    print(f"\n✓ Array input is {speedup:.1f}x faster!")
+    print()
+
+
+def main():
+    """Run all demonstrations."""
+    print("\n")
+    print("╔" + "═" * 68 + "╗")
+    print("║" + " " * 68 + "║")
+    print("║" + "  FRFcoord Multiple Point Input Support - Demo".center(68) + "║")
+    print("║" + " " * 68 + "║")
+    print("╚" + "═" * 68 + "╝")
+    print()
+
+    demo_single_point()
+    demo_array_input()
+    demo_different_coordinate_systems()
+    demo_individual_functions()
+    demo_performance_comparison()
+
+    print("=" * 70)
+    print("SUMMARY")
+    print("=" * 70)
+    print()
+    print("✓ FRFcoord supports single point AND multiple point inputs")
+    print("✓ No external loops needed for batch conversions")
+    print("✓ Array input is significantly faster than looping")
+    print("✓ All coordinate systems supported: FRF, State Plane, Lat/Lon, UTM")
+    print("✓ All transformation functions support arrays")
+    print()
+    print("This functionality is provided by pyproj >= 3.0.0")
+    print("No code changes needed - it already works!")
+    print("=" * 70)
+    print()
+
+
+if __name__ == "__main__":
+    main()