diff --git a/src/pymap3d/eci.py b/src/pymap3d/eci.py
index 1ee83e1..75d8111 100644
--- a/src/pymap3d/eci.py
+++ b/src/pymap3d/eci.py
@@ -4,7 +4,7 @@
 
 from datetime import datetime
 
-from numpy import array, atleast_1d, column_stack, cos, empty, sin
+import numpy as np
 
 try:
     import astropy.units as u
@@ -52,16 +52,19 @@ def eci2ecef(x, y, z, time: datetime) -> tuple:
         y_ecef = itrs.y.value
         z_ecef = itrs.z.value
     except NameError:
-        x = atleast_1d(x)
-        y = atleast_1d(y)
-        z = atleast_1d(z)
-        gst = atleast_1d(greenwichsrt(juliandate(time)))
-        assert x.shape == y.shape == z.shape, f"shape mismatch: x: ${x.shape}  y: {y.shape}  z: {z.shape}"
-        if gst.size > 1:
-            assert x.size == gst.size, f"shape mismatch: x: {x.shape}  gst: {gst.shape}"
-
-        eci = column_stack((x.ravel(), y.ravel(), z.ravel()))
-        ecef = empty((x.size, 3))
+        x = np.atleast_1d(x)
+        y = np.atleast_1d(y)
+        z = np.atleast_1d(z)
+        gst = np.atleast_1d(greenwichsrt(juliandate(time)))
+        assert (
+            x.shape == y.shape == z.shape
+        ), f"shape mismatch: x: ${x.shape}  y: {y.shape}  z: {z.shape}"
+        if gst.size == 1 and x.size != 1:
+            gst = np.broadcast_to(gst, x.shape)
+        assert x.size == gst.size, f"shape mismatch: x: {x.shape}  gst: {gst.shape}"
+
+        eci = np.column_stack((x.ravel(), y.ravel(), z.ravel()))
+        ecef = np.empty((x.size, 3))
         for i in range(eci.shape[0]):
             ecef[i, :] = R3(gst[i]) @ eci[i, :].T
 
@@ -109,15 +112,15 @@ def ecef2eci(x, y, z, time: datetime) -> tuple:
         y_eci = eci.y.value
         z_eci = eci.z.value
     except NameError:
-        x = atleast_1d(x)
-        y = atleast_1d(y)
-        z = atleast_1d(z)
-        gst = atleast_1d(greenwichsrt(juliandate(time)))
+        x = np.atleast_1d(x)
+        y = np.atleast_1d(y)
+        z = np.atleast_1d(z)
+        gst = np.atleast_1d(greenwichsrt(juliandate(time)))
         assert x.shape == y.shape == z.shape
         assert x.size == gst.size
 
-        ecef = column_stack((x.ravel(), y.ravel(), z.ravel()))
-        eci = empty((x.size, 3))
+        ecef = np.column_stack((x.ravel(), y.ravel(), z.ravel()))
+        eci = np.empty((x.size, 3))
         for i in range(x.size):
             eci[i, :] = R3(gst[i]).T @ ecef[i, :]
 
@@ -130,4 +133,4 @@ def ecef2eci(x, y, z, time: datetime) -> tuple:
 
 def R3(x: float):
     """Rotation matrix for ECI"""
-    return array([[cos(x), sin(x), 0], [-sin(x), cos(x), 0], [0, 0, 1]])
+    return np.array([[np.cos(x), np.sin(x), 0], [-np.sin(x), np.cos(x), 0], [0, 0, 1]])