Fix issue 876 (#891)

* Change return type from `auto` to `Eigen`  in "edge_method_cost_func.cpp"

* Use "round" in calculating the number of angles for Linspace

Author: rad-eng-59

cxx/isce3/antenna/EdgeMethodCostFunc.cpp

@@ -137,9 +137,8 @@ std::tuple<double, double, bool, int> rollAngleOffsetFromEdge(
                 "Near-range look angle shall be smaller than "
                 "far one by at least one prec!");
 
-    const auto ang_size =
-            static_cast<int>((look_ang_far - look_ang_near) / look_ang_prec) +
-            1;
+    const auto ang_size = static_cast<int>(
+            std::round((look_ang_far - look_ang_near) / look_ang_prec) + 1);
     auto look_ang = isce3::core::Linspace<double>::from_interval(
             look_ang_near, look_ang_far, ang_size);
 

cxx/isce3/antenna/ElNullAnalyses.cpp

@@ -90,8 +90,8 @@ tuple_ant genAntennaPairCoefs(
     auto el_space = std::min(*el_res_max, el_ang_step);
     auto el_start = idx_peak_left * el_ang_step + el_ang_start;
     auto el_stop = idx_peak_right * el_ang_step + el_ang_start;
-    auto num_idx =
-            static_cast<Eigen::Index>((el_stop - el_start) / el_space + 1);
+    auto num_idx = static_cast<Eigen::Index>(
+            std::round((el_stop - el_start) / el_space) + 1);
 
     Eigen::ArrayXd el_vec =
             Eigen::ArrayXd::LinSpaced(num_idx, el_start, el_stop);

tests/cxx/isce3/antenna/edge_method_cost_func.cpp

@@ -44,7 +44,7 @@ struct EdgeMethodCostFuncTest : public ::testing::Test {
             // add roll offset (perturbed)
             auto lka_ant_rad = lka_edge_rad + roll * md2r;
             // add a gain offset
-            auto gain_ant = polyvals(pf_ref, lka_ant_rad) + gain_ofs;
+            Eigen::ArrayXd gain_ant = polyvals(pf_ref, lka_ant_rad) + gain_ofs;
             pf_ant_vec.push_back(
                     isce3::math::polyfitObj(lka_edge_rad, gain_ant, 3, false));
         }
@@ -105,9 +105,9 @@ struct EdgeMethodCostFuncTest : public ::testing::Test {
     const double max_lka_edge_deg {34.0};
     const double prec_lka_edge_deg {1e-3};
     const int num_lka_edge {
-            static_cast<int>(
-                    (max_lka_edge_deg - min_lka_edge_deg) / prec_lka_edge_deg) +
-            1};
+            static_cast<int>(std::round((max_lka_edge_deg - min_lka_edge_deg) /
+                                        prec_lka_edge_deg) +
+                             1)};
 
     // gain offset in (dB) between relative EL power patterns extracted from
     // antenna and echo. the roll offset estimation is insensitive to this gain
@@ -125,8 +125,8 @@ struct EdgeMethodCostFuncTest : public ::testing::Test {
     // Build a 6-order polyminals of a relative antenna gain from gain (dB)
     // versus look angles (rad) to be used as a reference for building both
     // antenna and echo data
-    // These points are extracted from a realitic EL power pattern of ALOS1 beam
-    // #7.
+    // These points are extracted from a realistic EL power pattern of ALOS1
+    // beam #7.
     std::vector<double> gain {
             -2.2, -1.2, -0.55, -0.2, 0.0, -0.2, -0.5, -1.0, -2.0};
     std::vector<double> lka_deg {