Passive Control Networks

Networks of passive control points were established by geodetic agencies in federal and provincial governments over the past 100 years. As proximity to a monument was critical for access to the reference frame using terrestrial methods, several hundreds of thousands of monuments were established across Canada (Table 3).  The federal primary horizontal and vertical networks accounted for about half of these control points. More recently, 3D control points of the CBN and HPN networks were established to better serve users equipped with GPS. The federal CBN and provincial HPN network points were nominally spaced every 200 and 50 km. Since the early 1990’s, a few tens of thousands of 3D control points have been established by CGRSC agencies and occupied with GPS at least once.  Of these, a subset of about 160 CBN monuments have been re-observed periodically, nominally at 5 year intervals.

Table 3. Number of passive control points.

Agency   3D Horizontal Vertical
  CBN HPN HSN Federal Provincial Federal Provincial Federal
AB 21 1,160   14,000 27,500 9,800 *
BC 16 975   17,000 35,000 11,000  
MB 13 244 6,500 4,600 6,500 5,600 3,400
NB 6 135   300 26,000 3,700  
NL 6 4,200 7,000 3,600
NS 5 925   400 23,000 4,200 *
ON 33 220 10,300 44,000 125,000 15,000
PEI 2 21   100 4,746 1,100  
QC 30 1,700 21,300 12,000 36,000 14,000 10,000
SK 20 220 7,700 9,000 7,600 15,000
NT 10 10,000 1,900
YT 1 3,200 1,900

*Heights are published with the horizontal coordinates. No control points published with height information only.