From 24062d0417c82a85783475477cd6b040c9268a8f Mon Sep 17 00:00:00 2001
From: Dan Paulat <dpaulat@gmail.com>
Date: Sun, 25 Feb 2024 01:55:54 -0600
Subject: [PATCH] Add VIL-specific data level conversions

---
 .../wsr88d/rpg/product_description_block.hpp  |  5 +--
 .../wsr88d/rpg/product_description_block.cpp  | 31 +++++++++++++++++--
 2 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/wxdata/include/scwx/wsr88d/rpg/product_description_block.hpp b/wxdata/include/scwx/wsr88d/rpg/product_description_block.hpp
index c67ccbf2..d7973026 100644
--- a/wxdata/include/scwx/wsr88d/rpg/product_description_block.hpp
+++ b/wxdata/include/scwx/wsr88d/rpg/product_description_block.hpp
@@ -66,8 +66,9 @@ public:
    std::optional<DataLevelCode> data_level_code(std::uint8_t level) const;
    std::optional<float>         data_value(std::uint8_t level) const;
 
-   float log_offset() const;
-   float log_scale() const;
+   std::uint16_t log_start() const;
+   float         log_offset() const;
+   float         log_scale() const;
 
    units::angle::degrees<double> elevation() const;
 
diff --git a/wxdata/source/scwx/wsr88d/rpg/product_description_block.cpp b/wxdata/source/scwx/wsr88d/rpg/product_description_block.cpp
index 90385e88..f09a32b4 100644
--- a/wxdata/source/scwx/wsr88d/rpg/product_description_block.cpp
+++ b/wxdata/source/scwx/wsr88d/rpg/product_description_block.cpp
@@ -4,6 +4,7 @@
 
 #include <array>
 #include <istream>
+#include <numbers>
 #include <set>
 #include <string>
 
@@ -591,6 +592,20 @@ uint16_t ProductDescriptionBlock::number_of_levels() const
    return numberOfLevels;
 }
 
+std::uint16_t ProductDescriptionBlock::log_start() const
+{
+   std::uint16_t logStart = std::numeric_limits<std::uint16_t>::max();
+
+   switch (p->productCode_)
+   {
+   case 134:
+      logStart = p->halfword(33);
+      break;
+   }
+
+   return logStart;
+}
+
 float ProductDescriptionBlock::log_offset() const
 {
    float logOffset = 0.0f;
@@ -598,7 +613,7 @@ float ProductDescriptionBlock::log_offset() const
    switch (p->productCode_)
    {
    case 134:
-      logOffset = util ::DecodeFloat16(p->halfword(35));
+      logOffset = util::DecodeFloat16(p->halfword(35));
       break;
    }
 
@@ -612,7 +627,7 @@ float ProductDescriptionBlock::log_scale() const
    switch (p->productCode_)
    {
    case 134:
-      logScale = util ::DecodeFloat16(p->halfword(34));
+      logScale = util::DecodeFloat16(p->halfword(34));
       break;
    }
 
@@ -1007,6 +1022,18 @@ ProductDescriptionBlock::data_value(std::uint8_t level) const
          f = (level - dataOffset) / dataScale;
          break;
 
+      case 134:
+         if (level < log_start())
+         {
+            f = (level - dataOffset) / dataScale;
+         }
+         else
+         {
+            f = static_cast<float>(std::pow<double>(
+               std::numbers::e, (level - log_offset()) / log_scale()));
+         }
+         break;
+
       default:
          f = level * dataScale + dataOffset;
          break;