Testing USB GPS receiver

Locations of reference benchmark pillars used in testing

GPS on top of pillar at Brooks

I have an interest in GPS for a long time, and want to have one to enable me to geo-tag my photos taken on a trip. I bought one Canmore GT-750 (L) GPS receiver and data logger the size of a small match box, and tested it against the coordinates of some GPS reference benchmark pillars found along the Trans Canada Highway from Ottawa to Calgary. At Hearst, the GT-750 was put on top of the large Trimble GPS which was already installed on the pillar, at other sites, it was put on the metal plate on the top of the pillar. 


I found that


1. The range of the root mean squares of the differences in latitude is .17 to 2.15 metre,  in longitude is 0.49 to 2.07, and in height is 0.73 to 6.21.


2. Most of the large discrepancies are due to the persistent or systematic differences between the coordinates obtained from the GT-750 against the official data.











The following are the official coordinates of the pillar:



Site ID                                 Latitude                 Longitude         Height(m)
Hearst HRST RACS-GLCORS N49° 40' 02.7692" W83° 30' 39.7364" 229.26
Longlac 963011                         N49° 46' 46.5588" W86° 31' 01.6466" 286.26
Thunder Bay 963001                 N48° 27' 55.7537" W89° 13' 01.9316" 221.28
Winnipeg Pier A 89R001         N49° 51' 15.2912" W97° 28' 41.6968" 212.41
Brandon 95R500                 N49° 53' 09.2927" W99° 54' 41.0582" 373.82
Kendal 90V113                         N50° 20' 18.7147" W103° 36' 45.8817" 653.97
Swift Current  94V051         N50° 14' 57.8709" W107° 46' 09.2674" 798.87
Maple Creek 94V050                 N49° 59' 23.1078" W109° 28' 05.9277" 771.39
Brooks 481655                         N50° 39' 52.8629" W112° 07' 02.5191" 747.69

The following are the means (M) and standard deviation (Std) of the differences in seconds between the GPS readings of latitude (Lat), longitude (Long) and the official data:

Site ID                                M. Lat Std Lat M. Long Std Long

Hearst HRST RACS-GLCORS -0.0137 0.0112 0.0525 0.0222

Longlac 963011                          0.0587 0.0198 0.0959 0.0395

Thunder Bay 963001                  0.0707 0.0177 0.0801 0.0264

Winnipeg Pier A 89R001          0.0369 0.0102 0.0870 0.0025

Brandon 95R500                  0.0402 0.0171 0.0413 0.0262

Kendal 90V113                         -0.0472     0.0094 0.0578 0.0171

Swift Current  94V051         -0.0027 0.0050 0.0142 0.0521

Maple Creek 94V050             -0.0553 0.0074 0.0930 0.0228

Brooks 481655                         -0.0427 0.0155 -0.0078 0.0240

The following are the means (M) and standard deviation (Std) of the differences in metres between the GPS readings of latitude (Lat), longitude (Long), height and the official data:

Site ID                                 M. Lat Std Lat M. Long Std Long M. Height  Std Height

Hearst HRST RACS-GLCORS -0.4232 0.3459 1.0500 0.4438 6.1430    0.8874

Longlac 963011                          1.8130 0.6116 1.9113 0.7878 0.5162    1.1336

Thunder Bay 963001                  2.1840 0.5467 1.6400 0.7455 2.8849    0.7013

Winnipeg Pier A 89R001          1.1400 0.3151 1.5650 0.3190 3.2292    0.5020

Brandon 95R500                  1.2420 0.5282 0.8219 0.3224 0.4703    0.5629

Kendal 90V113                         -1.4580     0.2903 0.8319 0.3371 1.1999    0.3541

Swift Current  94V051         -0.0834 0.1544 0.2805 1.0290 0.7602    0.8847

Maple Creek 94V050          -1.7080 0.2286 2.0450 0.1430 1.7032    0.1846

Brooks 481655                         -1.3190 0.4788 0.1527 0.4699 3.2373    0.8084

The following are the root mean squares (RMS) of the differences in metres between the GPS readings of latitude (Lat), longitude (Long), height and the official data:

Site ID                                 RMS Lat    RMS Long RMS Height

Hearst HRST RACS-GLCORS 0.5466    1.1399         6.2067

Longlac 963011                         1.9134    2.0673         1.2456

Thunder Bay 963001                 2.2514    1.8015         2.9689

Winnipeg Pier A 89R001         1.1827    1.5972         3.2679

Brandon 95R500                 1.3497    0.8829         0.7335

Kendal 90V113                         1.4866    0.8976         1.2511

Swift Current  94V051         0.1755    1.0665         1.1664

Maple Creek 94V050             1.7232    2.0500         1.7132

Brooks 481655                         1.4032    0.4941         3.3367

The following is a plot of the difference of longitude and latitude (seconds) between the GPS readings and the official data at Longlac 963011. The sampling time is 10 seconds.

The following is a plot of the difference of altitude (metres) between the GPS readings and the official data at Longlac 963011. The sampling time is 10 seconds.