Use of Satellites or Drones for Imagery Collection

Introduction 🔗

Today, aerial imagery is available from a variety of sources, including traditional satellites, nano satellites, manned and unmanned aircrafts, balloons, and kites. This imagery can benefit humanitarian organisations in programming implementation, resource planning, community studies, and disaster response. Previously, the process of developing maps from imagery was painstakingly slow and it required a great deal of time from highly technically skilled individuals to patch different formatted images together. This decision making guide aims to take the acquired knowledge from UNICEF’s use of satellites and drones for imagery collection and provide a guide on the different technologies as well as when to use a particular mode over the other.

Decision-making matrix 🔗

The following tables provide a fact sheet on satellite and drone technology. When used together it will enable any technical or administrative decision maker to come to a quick and informed decision on which technology is best for any imagery needs.

Satellite imagery specifications; 🔗

Type	Sensor	Bands	Resolution	Coverage	Frequency
Commercial	Worldview3 (MAXAR)	Multi-spectral (8)	Pan-chromatic 31 cm (pan) 1.24 m (multi spectral)	Global	Revisit time of <1 day collecting up to 680,000 km2 per day
Commercial	Planet scope	R,G,B, NIR	3.7 m	Global	Revisit time < 1 day Collecting for the entire globe everyday
Commercial	ICEEYE	Synthetic Aperture Radar (SAR)	Up to 25cm	Global	20 hours
Commercial	Capella Space	SAR	Up to 30 cm	Global	Maximum hourly
Public	MODIS	Optical 36 bands	250 m	Global	1 day
Public	VIIRS	Optical 21 and DNB (night-time light)	375 m	Global	1 day
Public	ALOS-2 PALSAR	SAR	30 m	Global	14 days
Public	Sentinel	Optical and SAR	10 m	Global	8 days
Public	Landsat	Optical	30 m	Global	16 days

Drone Imagery Specifications 🔗

Turnaround time	Resolution	Coverage	Products
5 to 15 minutes to arrive at a site depending on distance of drone team from area of interest/impact	5cm per px for typical photogrammetric drone, Accuracy: 10m	40 Acres per flight (30 minutes) with typical quadcopter	Drone images and video
25 minutes from arrival at site to deliver initial images of site.	5cm per px, Accuracy: 10m	2,000 Acres per flight (90 minutes) with a typical fixed wing	Drone images and video
2 - 8 hours from demobilization	1cm per px, Accuracy: 2cm XY, 5cm Z		2D orthomosaic, 3D point cloud
3 – 20 hours from demobilization	1cm per px, Accuracy: 2cm XY, 5cm Z		Various types of analysis and CAD drawings

Performance Grid 🔗

Rating	Turnaround time	Resolution/px	Coverage Area	Recommended Mode
1 – 2	3 working days	1.5 m - 10 m+	100 km2 to1,000 km2	Satellite
3 – 4	2 working days	30 cm – 1.5 m	2 km2 to 20 km2	Fixed wing drone
5 – 6	5 hours	20 cm	1 km2	Fixed wing drone
7 – 8	60 minutes	10 cm	0.32 km2	Multi-copter drone
9 – 10	30 minutes	5 cm	0.004 km2 to 0.16 km2	Multi-copter drone