15. Property, plant and equipment:


	Land and		Leasehold						Furniture		Computer
	buildings		improvements		Equipment		Satellites		and fixtures		hardware		Total
Cost
Balance as at December 31, 2015	$	191.0	$	31.7	$	232.2	$	—	$	7.4	$	43.9	$	506.2
Additions		3.0		15.2		15.3		—		1.9		6.2		41.6
Disposals		—		(0.2)		(0.6)		—		(0.1)		(1.8)		(2.7)
Foreign currency translation		0.4		0.5		0.7		—		0.2		0.9		2.7
Balance as at December 31, 2016		194.4		47.2		247.6		—		9.4		49.2		547.8
Acquired from business combination (note 9)		0.5		42.0		35.0		577.9		1.2		39.2		695.8
Additions		2.3		15.7		24.9		6.3		0.3		8.8		58.3
Disposals		—		(0.1)		(0.3)		—		—		(1.7)		(2.1)
Foreign currency translation		1.0		1.0		1.4		—		0.3		2.8		6.5
Balance as at December 31, 2017	$	198.2	$	105.8	$	308.6	$	584.2	$	11.2	$	98.3	$	1,306.3
Accumulated depreciation
Balance as at December 31, 2015	$	11.1	$	17.2	$	89.0	$	—	$	5.1	$	32.5	$	154.9
Depreciation expense		4.0		3.2		21.8		—		0.7		4.3		34.0
Disposals		—		(0.2)		(0.5)		—		(0.1)		(1.8)		(2.6)
Foreign currency translation		0.1		0.2		0.4		—		0.1		0.7		1.5
Balance as at December 31, 2016		15.2		20.4		110.7		—		5.8		35.7		187.8
Depreciation expense		4.3		4.2		22.9		21.8		0.8		7.1		61.1
Disposals		—		(0.1)		(0.2)		—		—		(1.7)		(2.0)
Foreign currency translation		0.3		0.7		1.4		—		0.2		1.9		4.5
Balance as at December 31, 2017	$	19.8	$	25.2	$	134.8	$	21.8	$	6.8	$	43.0	$	251.4
Net book value
December 31, 2017	$	178.4	$	80.6	$	173.8	$	562.4	$	4.4	$	55.3	$	1,054.9
December 31, 2016	$	179.2	$	26.8	$	136.9	$	—	$	3.6	$	13.5	$	360.0

Property, plant and equipment includes $119.6 million (December 31, 2016 - $43.6 million) of expenditures for property under construction.

The net book value of assets under finance leases are as follows:


	December 31,		December 31,
	2017		2016
Computer hardware	$	5.2	$	4.6
Furniture and fixtures		7.2		0.1
	$	12.4	$	4.7

Satellite constellation

At December 31, 2017, the Company operated a constellation of five in-orbit and fully commissioned satellites and had one satellite constellation under construction. The satellites were acquired in the DigitalGlobe acquisition (note 9) and were initially recognized at fair value as of the acquisition date of October 5, 2017 using a replacement cost approach. The net book value of each satellite is as follows:


			Satellites
	Satellites		under
As at December 31, 2017	in-orbit		construction		Total
Cost	$	569.0	$	15.2	$	584.2
Accumulated depreciation		(21.8)		—		(21.8)
Net book value	$	547.2	$	15.2	$	562.4