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January 25, 2012

High Resolution Digital Aerial Imagery vs High Resolution Satellite Imagery – Part 2

by Aer0metrex_admin
10cm Digital aerial images flown after a flood event in Rochester, Queensland in Jan 2011

(Click here to go to the article “High Resolution Digital Aerial Imagery vs High Resolution Satellite Imagery – Part 1“)

(click images to enlarge)

Location accessibility:

 Aerial Imagery:

The reach of an aerial acquisition company is usually restricted to a specific area or country due to the fact that aircraft are based in a specific location. Remote survey locations attract higher mobilisation and logistical costs. Other countries can impose difficult conditions on aerial survey operations and military clearance has to be obtained for imaging in some countries.

 Satellite Imagery:

The major advantage of earth observation satellites is the possibility to acquire data virtually anywhere on the planet without considering border and logistical restrictions. However the geometry and look angle can be variable depending on where the satellite normally tracks relative to the survey area.

 

Tamanrasset Terra satellite image

Speed and Coverage:

 Aerial Imagery:

With the development of new large-format cameras, it is possible to acquire a large amount of data with a minimum number of runs. The processing time will depend directly on the number of frames but with advances in computing technologies such as cloud computing, processing time is decreasing. Aerial acquisition allows the capture of time-sensitive events as the acquisition team has full control over when the aircraft can fly and allows capture during specific windows of opportunity.

 Satellite Imagery:

High resolution satellites can acquire a large amount of data in a timely manner anywhere in the globe. The images acquired are processed quickly due to their small number. More satellite constellations are being developed to increase coverage, however, to capture a specific area, a delay of one to three days occurs due to the way satellites orbit the earth. Taking into account cloud-cover, it can be difficult to capture time-critical events.

 

10cm Digital aerial images flown after a flood event in Rochester, Queensland in Jan 2011

Cost;

 Aerial Imagery:

The cost of an aerial acquisition survey is not simple as it depends on many variables such as mobilisation cost, resolution, accuracy. This section will be the subject of a new article.

 Satellite Imagery:

Satellite acquisition costs are usually more straightforward to calculate than aerial imagery costs. At the difference of aerial acquisition, the price won’t change depending on the location to be captured. This is why pricing can directly be found on many satellite data providers’ websites. Depending on the tasking emergency an uplift of up to 100% can be added to the cost of acquisition.

 

10cm digital aerial imagery of a Mine pit wall - AEROmetrex


Top 5 Recommendations when choosing between satellite and aerial technology:

  • Data providers are not all equal. Make sure you ask for data samples and accuracy statements before making a decision.
  • Things evolve very quickly in this field and making an informed decision is not easy. Do your homework to find the right data for your application. Think outside of the box; just because you’ve always used one mapping technology does not mean it is still the best solution.
  • Compare apples with apples.
  • Always remember in GIS terms – Junk in – Junk Out.
  • Cost is important but don’t neglect other parameters when the time comes to make your decision. It costs more time and money to fix things later during a project than making sure the right data is selected from the start.

(Click here to go to the article “High Resolution Digital Aerial Imagery vs High Resolution Satellite Imagery – Part 1“)

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