feat(io/gpr): GPR 几何-通道横偏解析与采样深度换算

新增 geopro::io::gpr 两个纯 C++17 几何函数:
- parseChannelXOffsets: 解析 .ord 末列==1 的有效通道横向偏移
- depthOfSample: 按物理把采样序号换算为深度米(samples<=1 防除零)

含失败先行的单测,GprGeometry.cpp 接入 geopro_io_gpr,
test 接入 geopro_tests。

src/io/gpr/CMakeLists.txt

@@ -1,4 +1,4 @@
-add_library(geopro_io_gpr STATIC IprHeader.cpp IprbReader.cpp)
+add_library(geopro_io_gpr STATIC IprHeader.cpp IprbReader.cpp GprGeometry.cpp)
 target_include_directories(geopro_io_gpr PUBLIC ${CMAKE_SOURCE_DIR}/src)
 target_compile_features(geopro_io_gpr PUBLIC cxx_std_17)
 

src/io/gpr/GprGeometry.cpp

@@ -0,0 +1,33 @@
+#include "io/gpr/GprGeometry.hpp"
+
+#include <sstream>
+#include <string>
+#include <vector>
+
+namespace geopro::io::gpr {
+
+std::vector<double> parseChannelXOffsets(const std::string& ordText) {
+  std::vector<double> offsets;
+  std::istringstream lines(ordText);
+  std::string line;
+  while (std::getline(lines, line)) {
+    std::istringstream tok(line);
+    std::vector<std::string> cols;
+    std::string col;
+    while (tok >> col) cols.push_back(col);
+    if (cols.size() < 4) continue;       // 空行/列数不足，跳过
+    if (cols.back() != "1") continue;    // 末列==1 才是有效通道
+    offsets.push_back(std::stod(cols[1]));
+  }
+  return offsets;
+}
+
+double depthOfSample(int s, const IprHeader& h) {
+  if (h.samples <= 1) return 0.0;  // 防除零
+  const double timeNs = static_cast<double>(s) * h.timeWindowNs /
+                        static_cast<double>(h.samples - 1);
+  const double timeSec = timeNs * 1e-9;
+  return h.soilVelocity * timeSec / 2.0;
+}
+
+}  // namespace geopro::io::gpr

src/io/gpr/GprGeometry.hpp

@@ -0,0 +1,20 @@
+#ifndef GEOPRO_IO_GPR_GPRGEOMETRY_HPP
+#define GEOPRO_IO_GPR_GPRGEOMETRY_HPP
+
+#include <string>
+#include <vector>
+
+#include "io/gpr/IprHeader.hpp"
+
+namespace geopro::io::gpr {
+
+// 解析 .ord 文本，返回末列==1 的有效通道的横向偏移(第 2 列)，按文件顺序。
+std::vector<double> parseChannelXOffsets(const std::string& ordText);
+
+// 采样序号 s → 深度(米)。depth = soilVelocity[m/s] * (s * timeWindowNs/(samples-1) * 1e-9) / 2。
+// samples<=1 时返回 0 防除零。
+double depthOfSample(int s, const IprHeader& h);
+
+}  // namespace geopro::io::gpr
+
+#endif  // GEOPRO_IO_GPR_GPRGEOMETRY_HPP

tests/CMakeLists.txt

@@ -171,6 +171,7 @@ target_link_libraries(geopro_tests PRIVATE geopro_controller Qt6::Test)
 # io/gpr 层：.iprh 头解析 + .iprb B-scan 读取（纯 C++17，零 Qt/VTK）。
 target_sources(geopro_tests PRIVATE io/gpr/test_ipr_header.cpp)
 target_sources(geopro_tests PRIVATE io/gpr/test_iprb_reader.cpp)
+target_sources(geopro_tests PRIVATE io/gpr/test_gpr_geometry.cpp)
 target_link_libraries(geopro_tests PRIVATE geopro_io_gpr)
 
 add_subdirectory(spike)   # spike S3: banded contour 渲染验证

tests/io/gpr/test_gpr_geometry.cpp

@@ -0,0 +1,21 @@
+#include "io/gpr/GprGeometry.hpp"
+#include "io/gpr/IprHeader.hpp"
+#include <gtest/gtest.h>
+using namespace geopro::io::gpr;
+
+TEST(GprGeometry, ParsesActiveChannelOffsets) {
+  const std::string ord = "0 -0.686000 -1.5 1\n1 -0.581000 -1.5 1\n14 0 -1.5 0\n";
+  auto xs = parseChannelXOffsets(ord);
+  ASSERT_EQ(xs.size(), 2u);  // 仅 2 个有效(末列=1)
+  EXPECT_NEAR(xs[0], -0.686, 1e-6);
+  EXPECT_NEAR(xs[1], -0.581, 1e-6);
+}
+
+TEST(GprGeometry, DepthOfLastSampleMatchesPhysics) {
+  IprHeader h{};
+  h.samples = 821;
+  h.timeWindowNs = 160.352;
+  h.soilVelocity = 1e8;  // m/s
+  EXPECT_NEAR(depthOfSample(820, h), 8.0, 0.05);  // ~8m
+  EXPECT_NEAR(depthOfSample(0, h), 0.0, 1e-9);
+}