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Introduction

The primary purpose of this Lab experiment is to perform single-point positioning using satellite broadcast ephemeris data and receiver observations for a given epoch. The Least-Square Method has been used for estimating the receiver's coordinate and the receiver's clock offset.

The receiver's initial position is X0 = -2694685.473, Y0 = -4293642.366, Z0 = 3857878.924 (WGS 84 XYZ in meters), and the initial clock offset of the receiver is zero.

Instruction

The usage of the source code:

  1. Download the zip file and uncompressed.
  2. Set the current folder of Matlab to spp folder.
  3. Type *main* in command line windows.
The Frame of Codes
  1. readrcv.m: Read the rcvr.dat file and store the data in rcv struct.
  2. readeph.m: Read the eph.dat file and store the data in Eph_broadcast struct.
  3. eph2satxyz.m: Convert the orbit parameters to ECEF coordinate (The earth rotation has been considered, and the relativity effect also be considered).
  4. XYZ2BLH.m
  5. XYZ2NEU.m
  6. main.m: Using the Least-Square method to calculate the receiver's coordinate and clock offset.

Results

The ECEF position and the clock offset of satellites.

svid X (m) Y (m) Z (m) Clock offset (s)
5 -8855545.4737 -22060115.1685 -11922133.1713 0.00018907
6 -8087233.0607 -16945956.5996 18816198.5368 -8.3932e-08
17 -21277119.8022 -7467119.5023 14287505.0468 -0.0002049
30 -17713900.9391 -19797464.3067 19213.2028 -1.0041e-05
10 9027646.532 -12319233.163 21737387.4107 3.3248e-05
23 -19452319.1118 -16750376.9085 -6918519.6344 1.036e-05
22 -13649531.2661 8229504.3157 21122957.8349 0.00022268
26 6162910.1746 -25286774.5207 -3541191.2494 0.00028099

The iteration of this LS problem.

Iterations Position X,Y,Z changed (m) Receiver clock changed (s) Updated position ECEF (m)
1 dx = -5737.933 (m)
dy = 1099.090 (m)
dz = -2610.774 (m)		 dtr = 0.001733 (s) X = -2700423.406332
Y = -4292543.276071
Z = 3855268.150447
2 dx = -0.130 (m)
dy = -0.100 (m)
dz = 0.105 (m)		 dtr = -0.000000 (s) X = -2700423.536456
Y = -4292543.375690
Z = 3855268.255359
3 dx = -0.000 (m)
dy = 0.000 (m)
dz = 0.000 (m)		 dtr = 0.000000 (s) X = -2700423.536456
Y = -4292543.375690
Z = 3855268.255359

Reference

  1. ARINC Research Corporation. (2000). GPS Interface Control Document ICD-GPS-200 (IRN-200C-004): Navstar GPS Space Segment and Aviation User Interfaces.