Making Maps in the Dark

GIS Contributor


Aerial surveying company Bluesky International is using next generation thermal survey equipment to capture highly accurate measurements of relative heat loss from building and other structures across the UK at night.

The resulting thermal maps provide municipal authorities and other organisations with intelligence with which to address fuel poverty, reduce carbon emissions and improve energy efficiency.

Thermal imagery has even been used by the Police to identify properties used as cannabis factories where high temperatures are used to encourage growth.

Rachel Tidmarsh, Managing Director of Bluesky International, explores the technology that has made this possible and how this and other types of night time mapping are providing benefit.

Thermal sensors

The new thermal sensor has, unlike previous sensors that are based on technology designed for use in a laboratory or industrial plant environment, been specifically designed for challenging operating conditions.

Many traditional systems require continuous cooling of the camera environment and this can lead to variations in results and subsequent issues during post survey analysis over large geographical areas.

The new ‘microbolometer’ thermal camera can perform nearer to the real ambient temperature around the camera making it more suitable for use in aircraft flying at night.

As well as being designed to operate under conditions of rapidly changing ambient temperature the new sensor is also capable of measuring within the optimal spectral range required to assess the emissivity from building roofs.

A spectral range of 1.5-14 µm (1µm = 1 millionth of metre), a temperature range of -40ºC to +120ºC and a camera resolution of 1240 x 480 pixels combined with an advanced navigation and positioning system that allows geo-referencing of the resulting heat loss image to a range of 1 pixel, ensures unrivalled performance in the thermal infrared survey market.

Putting Technology to Work

The latest areas to be surveyed using this technology include the city of Leeds, parts of Lincolnshire, Nottinghamshire and Norfolk. Bassetlaw, a Nottinghamshire based local authority, is planning to use the data to reduce CO2 emissions in the area and educate the public on energy efficiency.

“Living in a safe, warm and well-maintained home is essential to enjoying a good quality of life,” commented Kerri Ellis, Sustainability Officer at Bassetlaw District Council, “and we have introduced a fuel poverty reduction campaign to support this objective.” She continued, “The thermal data will help us accurately identify individual properties at risk of fuel poverty and enable us to proactively target households for tailored advice.”

An image showing in red areas of heat loss in a residential street.

Bassetlaw District Council will overlay the digital thermal map in their GIS combining it with other housing related intelligence such as SAP ratings (Standard Assessment Procedure – a method for measuring the energy rating of residential properties used in the United Kingdom) and Warm Front (a scheme funded by the UK government to provide improvements in domestic heating and insulation) information.

The property specific intelligence will then be used to identify individual properties and streets at risk of fuel poverty, target Council resources efficiently and effectively across a largely rural population and to provide a benchmark for ongoing works.

Other English cities and towns that have commissioned thermal surveys include Birmingham, Hastings, Leicester and Peterborough. Calderdale and Luton meanwhile are examples of local authorities that have published their thermal maps online giving visitors to their websites an instant snapshot of how much heat is escaping through their roof.

Donald Bowler, Luton Borough Council’s Environmental Assessment Manager said, “The thermal images are a very good way of showing residents how much heat they are losing through the roofs of their homes. People can see how heat efficient their property is by its colour and they can compare its heat efficiency to neighbouring houses which may be the same type of building but are more heat efficient due to better roof insulation.”

An image showing in red areas of heat loss on a street map.
Map showing heat loss from homes created by Bluesky International

For those seeking further advice Luton Council works with Cocoon Your Home, a free, not-for-profit, helpline, that provides callers with at least two estimates from reputable professional installers, along with details of any council or government grants for which the resident may be eligible. “People may be worried that they cannot afford the up front costs of insulating their home, but all home owners and private tenants are entitled to discounted loft and cavity wall insulation which means they can start saving money from the day the insulation is installed and will keep saving money for as long as the property is standing,” continued Bowler.

Thermal surveys in warmer climates

Thermal surveys are also playing their part in warmer climates. Recently a thermal mapping project was completed as part of the Municipality of Dubai’s programme of sustainable development.

The resulting thermal map, which identifies contributing factors to the Urban Heat Island (UHI) such as asphalt, building materials and air conditioning vents, is being used to support a range of ‘cool and green’ environmental initiatives.

Covering more than 600 square kilometres of the emirate’s area 30,000 individual photographs were orthorectified and mosaiced into a single, seamless, map accurate image.  A series of analyses were conducted on the data to identify heat sources such as asphalt and building materials, prevalence of open spaces and heating, ventilation and air conditioning (HVAC) units.

Dubai Aerial Thermal Survey

The Dubai Aerial Thermal Survey was conducted on behalf of the Environment Department and Geographic Information Systems (GIS) Department of the Dubai Municipality.

Reported comments from the Director of the GIS Department Mohammed Abdullah Al Zaffin include “There are various reasons for experiencing different temperature levels in different locations. In urban areas, more roads mean more temperature as asphalt does not reflect the solar heat but absorbs it.” The results of the project are now with Environment Department, “Field visits are already being made in some areas and there are plans for more green initiatives to reduce the level of temperature.”

Over the last decade Dubai has been one of the fastest growing construction projects in the world with a growing array of world class sky scrapers and high tech buildings. The UHI effect is caused by a modification of the land surface, mainly through development projects that use materials that retain heat.

A secondary contributor to UHI’s is the waste heat generated by energy usage. UHIs can have far reaching implications for people’s health and quality of life and the issue in Dubai is being addressed strategically and various different levels and may include painting house roofs white and planting more trees.

Maximizing aerial image surveys

As has been evidenced in the traditional aerial survey market there are a number of ways to maximise the efficiency of the data capture element of a project.

An obvious solution is to capture more than one type of data either using the same sensor or through the addition of supplementary equipment. LiDAR (Light Detection and Ranging) and Colour Infrared (CIR) are commonly captured in conjunction with RGB imagery to complement and enhance the resulting photomaps.

So there are additional options available for the night time surveyor. Using specially developed survey equipment the location of street lights, illuminated road signs and other night time sources of light can be mapped at night.

These map accurate images can be used directly in a desktop mapping tool or GIS in exactly the same way as traditional survey images, providing additional intelligence for local authorities and other organisations that are responsible for lighting infrastructure.

A city at night from the air
A city at night from the air (Bluesky International).

Light emission maps will also provide an accurate base for asset inventories, condition assessments and to assist with the identification of units for routine maintenance or fault repair as well as light pollution assessment and energy optimisation for electricity plants. 

Additional applications of the night-time survey images are expected to include measurement of illumination for energy consumption evaluations and additional intelligence to support innovative projects to ‘dim’ or even switch off selected streetlights in an effort to save money and reduce carbon emissions.

Using advanced spatial queries and mapping techniques ‘Nightsky’ maps can also be used to provide an assessment of light pollution helping to reduce unnecessary illumination and focus lighting infrastructure where it is needed most.

More night time mapping applications

Just as the more traditional remote sensing market has exploded, boosted by new technology and applications of existing data, so too will the after dark survey industry.

When the sun goes down it is truly amazing just what can be mapped … habitat mapping of nocturnal animals, geological activity or even antisocial behaviour.

Editorial note: Visit the Bluesky International web site for more information about thermal imagery including white papers and sample data downloads.

The United Kingdom and Ireland at night (Bluesky International).
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