DATUMTRANSFORMATION

Set user-defined datum transformation parameters

Platform:

OEM719, OEM729, OEM7500, OEM7600, OEM7700, OEM7720, PwrPak7, CPT7, CPT7700, SMART7, SMART2

Use this command to add or remove user-defined datum transformations. Each entry converts from one geodetic datum in the GEODETICDATUMS list to another. Generally, “From” is the native service datum for one of the position types, such as ITRF2014 for TerraStar or Veripos, and “To” is a desired output datum. Entries are indexed by the pair “From” “To”.

The OUTPUTDATUM command must be sent for any user-defined transformations to take effect.

The receiver firmware includes a default set of datum transformations. These default transformations cannot be deleted, but can be overwritten with user-defined parameters. A default transformation that has been overwritten can be reverted to the default parameters by deleting the transformation. User-defined transformations will persist a factory reset; all user-defined transformations can be removed by sending FRESET USER_DATUM_TRANSFORMATION (see the FRESET command).

The transformation used by this command is the 7 parameter Helmert transformation:

Where:

X, Y, Z are the coordinates in the input datum

Xs, Ys, Zs are the coordinates in the output datum

Tx, Ty, Tz are the translation parameters corrected for translation rate (metres)

Rx, Ry, Rz are the rotation parameters corrected for rotation rate (radians)

s is the scale difference corrected for scale rate (unitless)

A given parameter P is corrected for rate:

P(t)=P(tr)+ Ṕ̇(tr) (t-tr)

Where:

tr is the reference epoch of the parameters

t is the current epoch

P(tr) is the parameter at the reference epoch

Ṕ̇̇(tr) is the rate of the parameter at the reference epoch

The entry contains the reference epoch, value of each parameter at the reference epoch and rate of each parameter at the reference epoch. Both the user-defined and default transformations are reported by the DATUMTRANSFORMATIONS log.

Message ID: 2297

Abbreviated ASCII Syntax:

DATUMTRANSFORMATION switch from to [epoch [tx [ty [tz [rx [ry [rz [scale [tx_vel [ty_vel [tz_vel [rx_vel [ry_vel [rz_vel [scale_vel]]]]]]]]]]]]]]]

ASCII Examples:

Save a new transformation to NVM:

DATUMTRANSFORMATION save ITRF2008 NAD83(MA11) 1997.0 0.908 -2.0161 -0.5653 28.971 10.42 8.928 1.1 0.0001 0.0001 -0.0018 -0.02 0.105 -0.347 0.08

Delete an existing transformation from NVM:

DATUMTRANSFORMATION delete ITRF2008 NAD83(MA11)

Field

Field Type

ASCII Value

Binary Value

Description

Format

Binary Bytes

Binary Offset

1

Command header

–

–

DATUMTRANSFORMATION header

This field contains the command name for abbreviated ASCII or the message header for ASCII (see page 1) or Binary (see page 1).

–

H

0

2

switch

SAVE

1

Save the datum transformation defined by this command.

Enum

4

H

DELETE

2

Delete the datum transformation.

3

from

 

Name of the From datum in the GEODETICDATUMS log.

Char[32]

Variable

H+4

4

to

 

Name of the To datum in the GEODETICDATUMS log.

Char[32]

Variable

Variable

5

epoch

1900.000 – 3000.000

Reference epoch of the parameters (decimal year)

Examples:

2011.00 = Jan 1, 2011

2011.19 = Mar 11, 2011

Double

8

Variable

6

tx

 

Translations at the reference epoch (metres)

Float

4

Variable

7

ty

 

Float

4

Variable

8

tz

 

Float

4

Variable

9

rx

 

Rotations at the reference epoch (milliarcseconds)

Float

4

Variable

10

ry

 

Float

4

Variable

11

rz

 

Float

4

Variable

12

scale

 

Scale difference at the reference epoch (parts per billion)

Float

4

Variable

13

tx_vel

 

Translation rates (metres/year)

Float

4

Variable

14

ty_vel

 

Float

4

Variable

15

tz_vel

 

Float

4

Variable

16

rx_vel

 

Rotation rates (milliarcsecond/year)

Float

4

Variable

17

ry_vel

 

Float

4

Variable

18

rz_vel

 

Float

4

Variable

19

scale_vel

 

Scale difference rate (parts per billion/year)

Float

4

Variable