Update modified DF389 field descriptions [AP-3747] (#1478)

# Description

@swift-nav/algint-team

Clarify the modified DF389 field descriptions.

# API compatibility

No risks for API compatibility, only updated and rectified field
descriptions.

## API compatibility plan

N/A

# JIRA Reference

https://swift-nav.atlassian.net/browse/AP-3747

Author: reimerix

HOWTO.md

@@ -56,8 +56,9 @@ typedef struct {
   s16 residual;
 
   /**
-   * Modified DF389. class 3 MSB, value 5 LSB. stddev = (3^class * (1 +
-   * value/16) - 1) * 10
+   * Standard deviation encoded using a similar method as RTCM DF389. The upper
+   * 3 bit are the class, the lower 5 bits are the value. Standard deviation
+   * [TECU] = (3^class * (1 + value/16) - 1) * 0.1 [TECU]
    */
   u8 stddev;
 } sbp_stec_residual_t;

README.md

@@ -54,8 +54,9 @@ typedef struct {
   s8 wet;
 
   /**
-   * Modified DF389. class 3 MSB, value 5 LSB. stddev = (3^class * (1 +
-   * value/16) - 1) [mm]
+   * Standard deviation encoded using a similar method as RTCM DF389. The upper
+   * 3 bit are the class, the lower 5 bits are the value. Standard deviation
+   * [mm] = (3^class * (1 + value/16) - 1) [mm]
    */
   u8 stddev;
 } sbp_tropospheric_delay_correction_t;

c/include/libsbp/ssr/STECResidual.h

@@ -256,8 +256,9 @@ data TroposphericDelayCorrection = TroposphericDelayCorrection
   , _troposphericDelayCorrection_wet  :: !Int8
     -- ^ Wet vertical delay. Add 0.252 m to get actual value.
   , _troposphericDelayCorrection_stddev :: !Word8
-    -- ^ Modified DF389. class 3 MSB, value 5 LSB. stddev = (3^class * (1 +
-    -- value/16) - 1)
+    -- ^ Standard deviation encoded using a similar method as RTCM DF389. The
+    -- upper 3 bit are the class, the lower 5 bits are the value. Standard
+    -- deviation [mm] = (3^class * (1 + value/16) - 1)
   } deriving ( Show, Read, Eq )
 
 instance Binary TroposphericDelayCorrection where
@@ -308,8 +309,9 @@ data STECResidual = STECResidual
   , _sTECResidual_residual :: !Int16
     -- ^ STEC residual
   , _sTECResidual_stddev :: !Word8
-    -- ^ Modified DF389. class 3 MSB, value 5 LSB. stddev = (3^class * (1 +
-    -- value/16) - 1) * 10
+    -- ^ Standard deviation encoded using a similar method as RTCM DF389. The
+    -- upper 3 bit are the class, the lower 5 bits are the value. Standard
+    -- deviation [TECU] = (3^class * (1 + value/16) - 1) * 0.1
   } deriving ( Show, Read, Eq )
 
 instance Binary STECResidual where

c/include/libsbp/ssr/TroposphericDelayCorrection.h

@@ -28,7 +28,11 @@ public class STECResidual extends SBPStruct {
     /** STEC residual */
     public int residual;
 
-    /** Modified DF389. class 3 MSB, value 5 LSB. stddev = (3^class * (1 + value/16) - 1) * 10 */
+    /**
+     * Standard deviation encoded using a similar method as RTCM DF389. The upper 3 bit are the
+     * class, the lower 5 bits are the value. Standard deviation [TECU] = (3^class * (1 + value/16)
+     * - 1) * 0.1
+     */
     public int stddev;
 
     public STECResidual() {}

docs/sbp.pdf

@@ -28,7 +28,11 @@ public class TroposphericDelayCorrection extends SBPStruct {
     /** Wet vertical delay. Add 0.252 m to get actual value. */
     public int wet;
 
-    /** Modified DF389. class 3 MSB, value 5 LSB. stddev = (3^class * (1 + value/16) - 1) */
+    /**
+     * Standard deviation encoded using a similar method as RTCM DF389. The upper 3 bit are the
+     * class, the lower 5 bits are the value. Standard deviation [mm] = (3^class * (1 + value/16) -
+     * 1)
+     */
     public int stddev;
 
     public TroposphericDelayCorrection() {}

haskell/src/SwiftNav/SBP/Ssr.hs

@@ -0,0 +1,6 @@
+/*!
+ * The buffer module from node.js, for the browser.
+ *
+ * @author   Feross Aboukhadijeh <[email protected]> <http://feross.org>
+ * @license  MIT
+ */

java/src/com/swiftnav/sbp/ssr/STECResidual.java

@@ -266,8 +266,9 @@ TroposphericDelayCorrectionNoStd.prototype.fieldSpec.push(['wet', 'writeInt8', 1
  * Fields in the SBP payload (`sbp.payload`):
  * @field hydro number (signed 16-bit int, 2 bytes) Hydrostatic vertical delay. Add 2.3 m to get actual value.
  * @field wet number (signed 8-bit int, 1 byte) Wet vertical delay. Add 0.252 m to get actual value.
- * @field stddev number (unsigned 8-bit int, 1 byte) Modified DF389. class 3 MSB, value 5 LSB. stddev = (3^class * (1 + value/16) -
- *   1)
+ * @field stddev number (unsigned 8-bit int, 1 byte) Standard deviation encoded using a similar method as RTCM DF389. The upper 3 bit
+ *   are the class, the lower 5 bits are the value. Standard deviation [mm] =
+ *   (3^class * (1 + value/16) - 1)
  *
  * @param sbp An SBP object with a payload to be decoded.
  */
@@ -329,8 +330,9 @@ STECResidualNoStd.prototype.fieldSpec.push(['residual', 'writeInt16LE', 2]);
  * Fields in the SBP payload (`sbp.payload`):
  * @field sv_id SvId space vehicle identifier
  * @field residual number (signed 16-bit int, 2 bytes) STEC residual
- * @field stddev number (unsigned 8-bit int, 1 byte) Modified DF389. class 3 MSB, value 5 LSB. stddev = (3^class * (1 + value/16) -
- *   1) * 10
+ * @field stddev number (unsigned 8-bit int, 1 byte) Standard deviation encoded using a similar method as RTCM DF389. The upper 3 bit
+ *   are the class, the lower 5 bits are the value. Standard deviation [TECU] =
+ *   (3^class * (1 + value/16) - 1) * 0.1
  *
  * @param sbp An SBP object with a payload to be decoded.
  */