TrackerTelemetry (Draft)

Overview

Draft

TrackerTelemetry is draft and subject to change.

This is the structure and behavior of TrackerTelemetry in Extended Telemetry

This message carries tracker operating state.

No GPS lock is required to send this message.

Headline Improvements

• No more RegularType1 + BasicTelemetry message usage required when combined with GpsTelemetry
  • Trackers can now fly unlimited channels, no longer limited to 5
  • More efficient use of bitspace and airtime

Also serves as a sign of life when no GPS lock while also carrying useful telemetry.

Additional Improvements

Data	Notes
Channel	Positive message ownership and fingerprint frequency reference source
Temperature	Improved temperature range from BasicTelemetry
Voltage	Improved voltage range from BasicTelemetry
Window Sequence Number	Improves monitoring reboot and purposeful no-send conditions
GPS Lock Type	Improved GPS Lock State (none, time, 3D)
GPS Location Refinement	Refines GpsTelemetry location resolution beyond 6-char maidenhead grid

Message Structure

The header, as explained in Header Fields, explains the whole message header structure.

The fields below are for when the HdrType indicates a TrackerTelemetry message.

The TrackerTelemetry message makes use of both Uniform and Segmented Field Encoding

Segmented fields are described in more detail below the message definition table.

Message Definition

The structure of the TrackerTelemetry fields

Field	Unit	LowValue	HighValue	StepSize	# Values
Id13	Idx	0	19	1	20
Temp	F	-80	64	[segmented]	28
Voltage	V	2.7	6.06	[segmented]	52
Window	SeqNo	1	6	1	6
GpsLockType	Enum	0	2	1	3
SubLat	Idx	0	33	1	34
SubLng	Idx	0	33	1	34

Field Id13Idx

Id13Idx values

This field serves to identify the channel the sender is configured with.

This allows you to confirm ownership of the message.

A confirmed message:

• Is unambiguously yours
• Serves as an excellent frequency reference for Fingerprint-identifying other messages which aren't confirmed already

This field identifies the channel when combined with:

• band
• id13
  • Channel Map columns have id13 values for a given channel
  • This field is the vertical index offset top-down within that ChannelMap column

Example for Id13Idx

Consider you are searching for messages on channel 483:

• Say the received message is:
  • band = 20m
  • id13 = Q4
  • Id13Idx = 3
• So at Id13Idx=3 (0-based indexing), index down vertically from id13=Q4 to find channel 483.

Because the message is stamped with channel-identifying information, you can consider this message confirmed yours.

Field TempF

A segmented field, so variable resolution within the range of values.

TempF segments

Range	Resolution	Description
-80 - 40 F	5 F	Main operating range
40 - 64 F	8 F	Higher-temperature region

Field VoltageV

A segmented field, so variable resolution within the range of values.

VoltageV segments

Range	Resolution	Description
2.7 - 3.1 V	0.08 V	Low-voltage region
3.1 - 5.26 V	0.06 V	Main operating range
5.26 - 6.06 V	0.08 V	High-voltage region

Field WindowSeqNo

WindowSeqNo values

Supports insight into:

• Reboot behavior (eg reset to 1 unexpectedly) and
• Purposeful no-send conditions (not sending in every 10-minute slot)
  • eg no GPS lock
  • eg power saving

Usage:

• This is a sequence of numbers from 1 through 6
• The first window sent is 1
• Each subsequent window transmitted in by the tracker increments this number by 1
• When the number exceeds the range wrap around to 1

Field GpsLockTypeEnum

GpsLockTypeEnum values

Distinguish between 3 states:

• 0 = No Lock
• 1 = Time Lock
• 2 = 3D Location Lock

Field SubLatIdx and SubLngIdx

SubLatIdx and SubLngIdx values

These values refine location within GpsTelemetry via:

• 34 latitude bins (cell height = 180 / 127 / 34 degrees)
• 34 longitude bins (cell width = 360 / 254 / 34 degrees)

Scheme	Cell Size	Lat Worst Error	Lng Worst Error	Worst-case Diagonal Error
6-char Maidenhead	5.75 mi × 2.88 mi	1.44 mi	2.88 mi	3.21 mi
127×254 + 34×34	2.88 mi × 2.88 mi	1.44 mi	1.44 mi	2.03 mi

Decoding these values depends on having GpsTelemetry location data available as the reference.

When this message can be sent

Send under numerous conditions

Suggested behavior is to be sent along with the GpsTelemetry message as part of a 2-message pair within a window.

It can be sent any number of times in any Extended Telemetry slot.