GPS

A GPS sensor that returns coordinates .

A GPS sensor which returns the position either in Blender or Geodetic coordinates.

This sensor always provides perfect data on the levels “raw” and “extended”. To obtain more realistic readings, it is recommended to add modifiers.

  • Noise modifier: Adds random Gaussian noise to the data

coordinates in Blender: x -> east and y -> north

The “heading” is Clockwise (mathematically negative).

Conversion of Geodetic coordinates into ECEF-r, LTP into ECEF-r and vice versa

Conversion of Geodetic coordinates into ECEF-r

To be able to simulate a GPS-sensor P (the Blender origin) must be defined in the properties in Geodetic coordinates (longitude, latitude, altitude). For the transformation [Psas] the coordinates must be in decimal degrees (no North, minutes, etc.). The result is a point x_0 in the ECEF-r coordinates.

Conversion of ECEF-r into LTP[Psas]

For this conversion x_0 is the base. A point x_e is given in the ECEF-r coordinates and the goal is to get x_t (=
x_e in the LTP-coordinates).

../../_images/conversion_coordinates1.png

1. Transform P (Blender origin, geodetic coordinates (stored in the properties)) into x0 (geocentric (ECEF-r) coordinates)

2. Calculate R_{te}[1] with longitude, latitude and altitude; matrix is the rotation part of the transformation

  1. Transform x_e into x_t with x_t = R_{te} * (x_e-x_0)

Conversion of LTP into ECEF-r

Known: P in Geodetic coordinates (→ x_0 in ECEF-r) and x_t in LTP-coordinates

Goal: x_e (= x_t in ECEF-r coordinates)

Based on the transformation described above the transformation is calculated with the transposed matrix R_{te}: x_e = x_0 +
(R_{te})' * x_t [Psas]

Conversion of ECEF-r into Geodetic coordinates

The last transformation is from ECEF-r coordinates into Geodetic coordinates. This transformation is calculated with the Vermeille’s method [FoIz]. The result is the point x_e in “GPS-coordinates” in radians.

Sources

“3.4 Vermeille’s Method(2002)” in “Comparative Analysis of the Performance of Iterative and Non-iterative Solutions to the Cartesian to Geodetic Coordinate Transformation”, Hok Sum Fok and H. Bâki Iz, http://www.lsgi.polyu.edu.hk/staff/zl.li/Vol_5_2/09-baki-3.pdf
“Conversion of Geodetic coordinates to the Local Tangent Plane”, Version 2.01, http://psas.pdx.edu/CoordinateSystem/Latitude_to_LocalTangent.pdf

Configuration parameters for gps

You can set these properties in your scripts with <component>.properties(<property1>=..., <property2>=...).

  • longitude (double, default: 0.0)

    longitude in degree [-180°,180°] or [0°,360°] of the Blender origin

  • latitude (double, default: 0.0)

    latitude in degree [-90°,90°] of the Blender origin

  • altitude (double, default: 0.0)

    altitude in m a.s.l. of the Blender origin

Available functional levels

Functional levels are predefined abstraction or realism levels for the sensor.

Services for GPS

  • get_local_data() (blocking)

    Returns the current data stored in the sensor.

    • Return value

      a dictionary of the current sensor’s data

  • get_configurations() (blocking)

    Returns the configurations of a component (parsed from the properties).

    • Return value

      a dictionary of the current component’s configurations

  • get_properties() (blocking)

    Returns the properties of a component.

    • Return value

      a dictionary of the current component’s properties

Examples

The following examples show how to use this component in a Builder script:

from morse.builder import *

robot = ATRV()

# creates a new instance of the sensor
gps = GPS()

# place your component at the correct location
gps.translate(<x>, <y>, <z>)
gps.rotate(<rx>, <ry>, <rz>)

# select a specific abstraction level (cf below), or skip it to use default level
gps.level(<level>)

robot.append(gps)

# define one or several communication interface, like 'socket'
gps.add_interface(<interface>)

env = Environment('empty')

Other sources of examples

(This page has been auto-generated from MORSE module morse.sensors.gps.)