diff --git a/src/compass/s1_geocode_slc.py b/src/compass/s1_geocode_slc.py
old mode 100755
new mode 100644
diff --git a/tests/prep.py b/tests/prep.py
new file mode 100644
index 00000000..a9d8eaa1
--- /dev/null
+++ b/tests/prep.py
@@ -0,0 +1,210 @@
+import datetime
+import pytest
+from types import SimpleNamespace
+
+import isce3
+import numpy as np
+from osgeo import gdal
+from s1reader.s1_burst_slc import Doppler, Sentinel1BurstSlc
+
+def expected_height_dem(cfg):
+    params = cfg.test_params
+
+    # define geogrid in degrees
+    lon0 = np.degrees(params.lon0) #- params.omega / 2
+    lat0 = np.degrees(params.lat0) #- params.omega / 2
+    omega = np.degrees(params.omega)
+    geo_trans = [lon0, omega, 0.0, lat0, 0.0, omega]
+
+    length = 1
+    width = params.n_samples#+ 1
+
+    # create DEM empty file
+    dem_raster = isce3.io.Raster(params.dem, width, length, 1,
+                                 gdal.GDT_Float32, 'GTiff')
+    dem_raster.set_geotransform(geo_trans)
+    dem_raster.set_epsg(params.epsg)
+    del dem_raster
+
+    # populate empty DEM with expected LLH values
+    data = np.array(cfg.expected_llh[:,2])[np.newaxis, ...]
+    ds = gdal.Open(params.dem, gdal.GA_Update)
+    ds.GetRasterBand(1).WriteArray(data)
+    ds = None
+
+
+def solve_geocentric_lat(slant_range, params):
+    temp = 1 + params.h_sat / params.ellipsoid.a
+    temp1 = slant_range / params.ellipsoid.a
+    temp2 = slant_range / (params.ellipsoid.a + params.h_sat)
+
+    cosang = 0.5 * (temp + (1.0/temp) - temp1 * temp2)
+    angdiff = np.arccos(cosang);
+
+    look_side_int = 1 if params.look_side == isce3.core.LookSide.Left \
+        else -1
+    if (look_side_int * params.omega > 0):
+        x = params.lat0 + angdiff
+    else:
+        x = params.lat0 - angdiff
+
+    return x
+
+
+def compute_orbit(params):
+    # Setup orbit
+    statevecs = []
+    clat = np.cos(params.lat0)
+    slat = np.sin(params.lat0)
+    sat_h = params.ellipsoid.a + params.h_sat
+    for ii in range(params.n_sv):
+        total_delta_t = ii * params.orbit_dt
+        t = params.orbit_start + datetime.timedelta(seconds=total_delta_t)
+
+        lon = params.lon0 + params.omega * total_delta_t
+
+        pos = [sat_h * clat * np.cos(lon),
+               sat_h * clat * np.sin(lon),
+               sat_h * slat]
+
+        vel = [-params.omega * pos[1],
+                params.omega * pos[0],
+                0.0]
+
+        sv = isce3.core.StateVector(isce3.core.DateTime(t), pos, vel)
+        statevecs.append(sv)
+
+    # use list of stateVectors to init and return isce3.core.Orbit
+    time_delta = datetime.timedelta(days=2)
+    ref_epoch = isce3.core.DateTime(params.sensing_start - time_delta)
+
+    return isce3.core.Orbit(statevecs, ref_epoch)
+
+
+def common_params(lat):
+    params = SimpleNamespace()
+    sensing_start = "2017-02-12T01:12:35.0"
+    orbit_start = "2017-02-12T01:12:30.0"
+    fmt = "%Y-%m-%dT%H:%M:%S.%f"
+    params.sensing_start = datetime.datetime.strptime(sensing_start, fmt)
+    params.orbit_start = datetime.datetime.strptime(orbit_start, fmt)
+    params.lon0 = 0.0
+    params.lat0 = np.radians(lat)
+    params.omega = np.radians(0.001)
+    params.n_sv = 10
+    params.n_samples = 20
+    params.h_sat = 700000.0
+    params.slant_range0 = 800000.0
+    params.d_slant_range = 10.0
+    params.az_time0 = 5.0
+    params.d_az_time = 2.0
+    params.orbit_dt = 10.0
+    params.epsg = 4326
+    params.look_side = isce3.core.LookSide.Right
+    params.ellipsoid = isce3.core.make_projection(params.epsg).ellipsoid
+    params.orbit = compute_orbit(params)
+    params.dem = "expected_height_dem.tif"
+    return params
+
+
+def create_burst(params):
+
+    # place holder value
+    dont_matter_for_now = 0
+
+    radar_freq = dont_matter_for_now
+    wavelength = 0.24
+    azimuth_steer_rate = 0.024389943375862838
+    slant_range_time = dont_matter_for_now
+    iw2_mid_range = dont_matter_for_now
+    range_sampling_rate = dont_matter_for_now
+    shape = (1, params.n_samples)
+    az_fm_rate = dont_matter_for_now
+    doppler = Doppler(isce3.core.Poly1d([1]), isce3.core.LUT2d())
+    rng_processing_bandwidth = dont_matter_for_now
+    pol = 'vv'
+    burst_id = 't00_iw1_b000'
+    platform_id = dont_matter_for_now
+    center_pts = ()
+    boundary_pts = []
+    orbit_dir = str(dont_matter_for_now)
+    tiff_path = dont_matter_for_now
+    i_burst = dont_matter_for_now
+    first_valid_sample = dont_matter_for_now
+    last_sample = dont_matter_for_now
+    first_valid_line = dont_matter_for_now
+    last_line = dont_matter_for_now
+    range_window_type = dont_matter_for_now
+    range_window_coeff = dont_matter_for_now
+    i_burst = dont_matter_for_now
+    range_window_type = str(dont_matter_for_now)
+    range_window_coeff = dont_matter_for_now
+    rank = int(dont_matter_for_now)
+    prf_raw_data = dont_matter_for_now
+    range_chirp_ramp_rate = dont_matter_for_now
+
+    burst = Sentinel1BurstSlc(params.sensing_start, radar_freq, wavelength,
+                              azimuth_steer_rate, params.d_az_time,
+                              slant_range_time, params.slant_range0, iw2_mid_range,
+                              range_sampling_rate, params.d_slant_range,
+                              shape, az_fm_rate, doppler,
+                              rng_processing_bandwidth, pol, burst_id,
+                              platform_id, center_pts,
+                              boundary_pts, params.orbit, orbit_dir,
+                              tiff_path, i_burst, first_valid_sample,
+                              last_sample, first_valid_line, last_line,
+                              range_window_type, range_window_coeff,
+                              rank, prf_raw_data, range_chirp_ramp_rate)
+
+    return burst
+
+
+def compute_expected_llh(test_params):
+    i = np.arange(test_params.n_samples)
+    ellipsoid = test_params.ellipsoid
+    az_time = test_params.az_time0 + i * test_params.d_az_time
+    slant_range = test_params.slant_range0 + i * test_params.d_slant_range
+    lon = test_params.lon0 + test_params.omega * az_time
+    c_lon = np.cos(lon)
+    s_lon = np.sin(lon)
+    lat = solve_geocentric_lat(slant_range, test_params)
+    c_lat = np.cos(lat)
+    s_lat = np.sin(lat)
+    xyz_vec = np.vstack([ellipsoid.a * c_lat * c_lon,
+                         ellipsoid.a * c_lat * s_lon,
+                         ellipsoid.a * s_lat])
+    llh = np.array([ellipsoid.xyz_to_lon_lat(xyz_vec[:,i])
+                    for i in range(test_params.n_samples)])
+    return llh
+
+
+def cfg_45_lat():
+    # manually populate namespace identical with attribs expected by s1_*
+    cfg = SimpleNamespace()
+
+    # retrieve test-defining parameters
+    cfg.test_params = common_params(45)
+
+    # compute expected LLH for (1) test comparison (2) DEM population
+    cfg.expected_llh = compute_expected_llh(cfg.test_params)
+
+    # create and set DEM raster
+    expected_height_dem(cfg)
+
+    # set rdr2geo params
+    rdr2geo_params = SimpleNamespace()
+    rdr2geo_params.threshold = 1e-8
+    rdr2geo_params.numiter= 50
+    rdr2geo_params.lines_per_block = 100
+    rdr2geo_params.extraiter = 25
+    rdr2geo_params.compute_mask = True
+    cfg.rdr2geo_params = rdr2geo_params
+
+    # make list with single burst
+    cfg.bursts = [create_burst(cfg.test_params)]
+    cfg.dem = cfg.test_params.dem
+    cfg.gpu_enabled = False
+    cfg.gpu_id = 0
+    cfg.product_path = 'test_out'
+
+    return cfg
diff --git a/tests/test_rdr2geo.py b/tests/test_rdr2geo.py
new file mode 100644
index 00000000..b8ba6bf1
--- /dev/null
+++ b/tests/test_rdr2geo.py
@@ -0,0 +1,35 @@
+#!/usr/bin/env python3
+import pytest
+
+from compass import s1_rdr2geo
+import numpy as np
+from osgeo import gdal
+
+import prep
+
+def get_rdr2geo_output(cfg):
+    burst = cfg.bursts[0]
+    burst_id = burst.burst_id
+    date_str = str(burst.sensing_start.date())
+    topo_path = f'{cfg.product_path}/{burst_id}/{date_str}/topo.vrt'
+    ds = gdal.Open(topo_path)
+    llh = np.vstack([ds.GetRasterBand(i+1).ReadAsArray() for i in range(3)])
+    return llh.transpose()
+
+def test_45_lat_rdr2geo():
+    # set up test configuration for 45 degree latitude
+    cfg = prep.cfg_45_lat()
+
+    # run s1_rdr2geo with configuration from above
+    s1_rdr2geo.run(cfg)
+
+    # retrieve and print rdr2geo output
+    computed_llh = get_rdr2geo_output(cfg)
+    print(computed_llh, computed_llh.shape)
+
+    # print analytical solution
+    print(cfg.expected_llh, cfg.expected_llh.shape)
+
+
+if __name__ == '__main__':
+    test_45_lat_rdr2geo()