Latest News

Xerra joins NASA PACE early adopter programme

By Xerra News Cat

Xerra senior scientist Dr Moritz Lehmann has been accepted to the NASA PACE early adopter programme, along with scientists from across the globe in order to advance research of global ocean colour, biogeochemistry, and ecology. 

Using data from the PACE mission, Dr Lehmann will be able to determine the extent and duration of harmful algal blooms in Aotearoa’s coastal waters and large lakes, in ways that have previously not been possible. 

These blooms affect both commercial and recreational activities, in addition to harming ecological function and ecosystem health. Monitoring the patterns of harmful algal blooms requires an understanding of dispersion and growth dynamics and species distribution. The identification of potentially toxic versus non-toxic algae is possible with space-borne, high spectral resolution data, like that which will be collected by the PACE satellite sensor.  

Working alongside the University of Waikato and Cawthron Institute, this collaboration aims to establish a research project to support routine monitoring of harmful algal blooms, as well as improve alert systems and inform the design of restoration activities.

Dr Lehman says he’s really excited to be involved in the early adopter programme. “It enables us as New Zealand scientists to communicate with NASA on how and why we are using their data. The programme also provides a forum for collaboration with the international scientific community to determine how PACE data can be used for improved monitoring and alert systems to protect the health and livelihoods of New Zealanders.” 

About PACE 

PACE is NASA’s Plankton, Aerosol, Cloud, ocean Ecosystem mission, currently in the design phase of mission development. It is scheduled to launch in 2022, extending and improving NASA’s over 20-year record of satellite observations of global ocean biology, aerosols (tiny particles suspended in the atmosphere), and clouds.

PACE will advance the assessment of ocean health by measuring the distribution of phytoplankton, tiny plants and algae that sustain the marine food web. It will also continue systematic records of key atmospheric variables associated with air quality and Earth’s climate.

PACE’s Ocean Colour Instrument will be the most advanced for observing ocean colour in NASA’s history. Observing chlorophyll from space has a long heritage – the first ocean colour satellite, NASA’s Coastal Zone Color Scanner (CZCS) was launched in 1978. 

PACE represents a leap forward because it will view a very broad spectrum from 350 to 885 nanometer (nm) wavelengths at 5 nm intervals – making it hyperspectral. The range that PACE’s instruments will observe includes the UV (350-400 nm), visible (400-700 nm), and near-infrared (700-885 nm), as well as several shortwave infrared bands. Thus, the OCI will provide an unprecedented view of the ocean without the “blind spots” of previous sensors.

For more information on the PACE science mission, please visit the NASA PACE website, where the above text has been sourced from.

Sunsetting Xerra Gateway

By Xerra News Cat

From 10 July 2020 Xerra Gateway will no longer be available for accessing current and archived Sentinel satellite data from the Copernicus Programme.

Xerra Gateway was a pilot in order to determine if there was sufficient demand for Sentinel products in New Zealand. Unfortunately, the uptake for the pilot wasn’t sufficient to continue this as a stand-alone product.

For continued access to Sentinel data, we recommend visiting Geoscience Australia’s Sentinel Australasia Regional Access data portal.

Xerra still offers a variety of commercial satellite imagery and products from Airbus, Maxar and Planet. We also provide training on how best to utilise EO data in your workflow. 

It’s been our pleasure to offer Xerra Gateway, albeit for a limited time, to our local community of remote sensing specialists and enthusiasts. We appreciate both your interest and use of the service, and any feedback you may have given us to help improve the site—thank you.

Beneath the smoke of bushfires

By Xerra News Cat

By using satellite imagery collected in the infrared part of the spectrum scientists can often trace the fire-fronts in bushfires, despite the thick layers of smoke blanketing the area. That is, in the infrared we can see through the smoke, which can help determine how and where the fires are burning. We expect this is what many of our Australian colleagues are doing at this moment as support to emergency services.

The images supplied here were collected by the European Sentinel-2A satellite on a pass over New South Wales, Australia on January 3rd, and processed by our scientists here at Xerra.

The image below is a ‘normal’ colour mix for the region around Jervis Bay, Nowra and Ulladulla, south of Sydney on the NSW coast. That is, this image is similar to what an astronaut might see (and photograph using a regular camera) from the Space Station.

Sentinel-2A satellite image of part of the NSW coast obtained on January 3rd with a ‘normal’ colour mix of the red, green and blue bands of the visible spectrum. In this image, the smoke obscures the fire-fronts that lie below.

By using an image obtained by the same satellite but at a wavelength of 2.2 microns (in the short-wave infrared [SWIR] part of the electromagnetic spectrum), one sees something quite different, as below.

A SWIR image of the same region as in the preceding image, scaled from black (low intensity) to yellow/orange (high intensity). In the SWIR the sensor ‘sees’ through the clouds and smoke, and detects the radiation being emitted by the active fires.

Clouds obscure our ability to see the actual fires in the visible part of the spectrum, so that all we see is reflected sunlight. Whereas in the infrared, we can not only see through the clouds but also we can see the electromagnetic radiation being emitted by the active fires.

*Data or imagery, such as the Sentinel images above are freely available from Xerra Gateway, for the use of researchers and others in New Zealand.

A new source of Sentinel imagery—Xerra Gateway

By Xerra News Cat

Today marks the launch Xerra Gateway, our New Zealand satellite data repository. Check it out here:

Improving access to Earth observation and satellite data, and developing products and services that deliver insights from this data, helps support evidence-informed decision and policy-making throughout the regions, and has an important role to play in the growth of New Zealand’s space economy.

Xerra Gateway is built in partnership with Geoscience Australia and the European Union’s Copernicus Programme. The site provides local scientists, researchers, and remote sensing and GIS specialists with easy access to Sentinel satellite imagery of New Zealand.

Our have spent time re-designing the user interface, improving both the search and download processes. Although the site is tailored to those in the science and remote sensing communities, the new interface ensures the public and citizen scientists can easily search the comprehensive archive of satellite images over Aotearoa.

The site also boasts faster download speeds, in comparison to other Sentinel data hubs. Dr Moritz Lehmann, our Senior Scientist at Xerra, has used the site regularly throughout its beta phase.

“Xerra Gateway is my first stop when looking for data from Copernicus’s Sentinel satellites,” says Dr Lehmann. “The interface is easy to understand and I like that the large browse images provide an immediate impression of the suitability of the images. One real advantage is that data from Xerra Gateway downloads way faster than from the Copernicus Hub hosted in Europe.”

Dr Lehmann is using the Sentinel images he downloads to monitor New Zealand’s lakes for water colour and the presence of cyanobacteria. This work is vital in helping councils increase the coverage and frequency of lake health monitoring in their region. Currently only 3% of Aotearoa’s lakes are regularly monitored for water quality. We want to help make every environmental monitoring dollar stretch further, and expand water quality monitoring to every lake in New Zealand.

Other applications for Sentinel satellite imagery can include sustainable forest management (deforestation detection, forest type classification and biomass estimation), mapping the colour of the Earth’s surface, measuring wave height, recording ocean and land surface temperatures, and climate monitoring.

Anyone can access the satellite data archive by visiting and creating a free login. From there it is easy to search and download images from the past years, months and days.  Xerra Gateway is regularly updated with new imagery of New Zealand, often within six hours of the Sentinel satellite overpasses.

Welcome to Dave Moskovitz

By Xerra News Cat

We’d like to welcome Dave Moskovitz to the Xerra Board of Directors. Dave started the role in early October and joins the Chair of the Board, Stephen Davies Howard, Maria King, Dr Ian Boddy and Melanie Templeton.

Dave brings a wealth of experience in the startup and entrepreneurial space to the Board, with a background in helping Kiwi entrepreneurs turn their ideas into a reality and enter into the overseas market. Recently Dave has been involved with a number of startups in and beyond the STEM (science, technology, engineering and maths) space. These startups use big data, AI, and visualisation to bring about a better society, while at the same time delivering the strong commercial outcomes that are necessary to create a sustainable business and investment returns. He says, “Helping these Kiwi businesses develop offshore markets has been a key part of this.”

When asked why he chose to apply for the Xerra Board of Directors role, Dave replied, “Xerra’s focus on using Earth observation data to bring about better sustainability for New Zealand and the planet seemed like a natural fit for my vision of the world we could be living in.”

We’re delighted to have Dave on board and look forward to working with him as we drive towards a sustainable future for both our organisation and New Zealand.

Finally, the Spark Needed to Ignite Innovation in Central Otago

By Xerra News Cat

Xerra is the very first company in the country to get commercial access to Spark’s new 5G network. Spark approached Xerra specifically because of the connectivity challenges that have plagued the Earth Observation Institute as it’s tried to establish itself in the Big Data space from its headquarters in Alexandra—a city that until now hasn’t had access to broadband fibre.

“This is a game-changer for us,” says Xerra CEO, Steve Cotter. Since day one, Xerra has explored a variety of options in hopes of securing the connectivity that in-house researchers and engineers require to do their work. Every avenue turned out to be a dead-end until Steve got the phone call from Spark. “We work with large data sets and it could take us four hours to download one image. Now, we can do it in four minutes,” he says. While Xerra is the first to be switched “on” to the 5G network, other Alexandra businesses and organisations will soon follow.

5G and fibre are exactly the kinds of technology, Cotter says, that will enhance the region’s ability to attract people who want to live and work in Central Otago. Until now, many have faced more limited employment choices because of the challenges of getting access to the necessary connectivity. For Xerra, that’s included not just its employees, but also their employees’ partners and spouses who need jobs too, before being able to make the commitment to move. This advancement will open the door to new remote working options, if they can’t find work locally.

Cotter points out that high-speed wireless broadband delivered by 5G and fibre is “the technological spark that’s needed to lay the groundwork for success if you want to achieve grand visions.”

Spark’s rollout of 5G in Alexandra kicks off a regional plan bringing 5G wireless broadband services to 5 other communities by Christmas.

“This is the kind of connectivity required to run a world-class science research institute in regional New Zealand. For us, it means people can enjoy a Central Otago lifestyle but also pursue a rewarding scientific career. And it’s the key to growing greater prosperity in the regions.”

The 5G announcement is also concurrent with the final fibre installations in Alexandra, which is a significant milestone for both Xerra and the local community.

Xerra successful in two joint MBIE Endeavour Fund bids: Forest flows & 3D change detection

By Xerra News Cat

Xerra has secured a couple of slices of a $241 million dollar pie—funding to support what the government refers to as “excellent research proposals that will provide the highest impacts”. Both bids are collaborative efforts spearheaded by partner agencies. They are among 71 projects awarded funding in an announcement on Tuesday, 17 September by Research, Science and Innovation Minister Megan Woods.

One proposal that got the green light is a $1M Smart Ideas project to help develop new 3D-change maps of New Zealand. Xerra’s Principal Scientist, Dr Dave Kelbe, will be supporting the University of Otago, along with GNS Science, Land Information New Zealand and Meridian Energy. The project will produce what Dr Pascal Sirguey of the University of Otago, and the Principal Investigator for the project calls, “unique, previously unavailable, land surface data.” He points out that this will place New Zealand “at the forefront of 3D-change detection”.

Being able to see topographic variations in our environment over time with unprecedented detail and sub-metre accuracy will allow environmental managers to make more informed decisions about managing natural resources in a safe, sustainable, and efficient way.

The other proposal that Xerra will be supporting is the Forest Flows project, a $13.7M Research Programme led by Scion, which also brings together the Universities of Auckland and Waikato, NIWA and international institutions. Its aim is to figure out exactly how planted forests impact our water.

In light of the One Billion Trees Programme and the government’s newly released National Policy Statement for Freshwater Management, this programme will develop a fast and accurate way to measure how much water is used by, evaporates from or flows through planted forests, leading to better management of our natural resources.

Xerra’s scientists will provide remote sensing measurements and data science expertise to help develop 3D spatial water quantity and quality models. These will help maximise New Zealand’s water supply, improve our water quality and ensure regional water security. Data generated will also help protect primary sector productivity, providing critical information to the timber industry.

Xerra CEO Steve Cotter says both projects are squarely in line with Xerra’s mission to provide insights that are a catalyst for change, adding that they also “reflect the high value we place on science collaboration with other institutions.” He adds that it’s a testament to the hard work of the newly appointed Xerra team, to see success with multiple joint Endeavour Fund proposals.

“I’m looking forward to seeing these new collaborative projects deliver the positive impact that we know space-based data and artificial intelligence can achieve.”

For additional information contact:
021 136 7702

Dr Pascal Sirguey
University of Otago

Calibrating satellite imagery using ground-based data collection

By Xerra News Cat

Satellite imagery is revolutionising how we see our world in manifold ways. Looking down from orbit has a drawback, however, as the intervening atmosphere, even when cloudless, adds some scattered sunlight for which allowances must be made.

At Xerra, in collaboration with the University of Waikato, NASA and the European Space Agency (ESA), we are gathering data in Aotearoa New Zealand that help the development of methods to remove the effect of the atmosphere. This is part of a global project to improve calibration and exploitation of satellite imagery for environmental monitoring and a range of agricultural and commercial applications.

Sensors onboard the Landsat 8 (NASA/US Geological Survey) and Sentinel-2 and Sentinel-3 satellites (ESA and the European Commission) detect sunlight reflected by the ground. This imagery can be analysed to derive important characteristics of the ground cover, such as the extent of forests and logging operations, the health of crops, the built-up area in development zones, and algal blooms in lakes, rivers and oceans.

However, the data collected by the satellites is not enough to get a full picture. Satellite operators and data providers require information collected at ground level to calibrate and validate the data collected from space. This is called ‘ground-truthing’.

How does the atmosphere impact satellite data collection?

The radiation detected from a satellite contains a large atmospheric signal – sunlight scattered by the air between the orbiting satellite and the ground (just as the sky looks bright and blue to us as we look upwards). Correction for this atmospheric scatter is required if scientists are to be able to identify the precise characteristics of the ground and water below.

Absorption and scattering by air molecules, and particles such as dust and aerosols, change the intensity and the spectral shape (colour) of light received by a satellite. These processes have to be accounted for if the satellite imagery is to be used for deriving information about the target areas below.

Correcting for atmospheric effects over inland and coastal waters is particularly challenging for various reasons, including the relatively low reflectivity of water (it looks darker than land when viewed from high above), stray-light effects from land areas adjacent to the water bodies, and also scattering of light by particles in the water which can mimic aerosol scattering.

So-called atmospheric correction is an active area of research globally, and several approaches are being developed by different teams. Some of these methods, which are applied to Sentinel-2 and Landsat 8 imagery, are formally validated and compared by an international collaborative initiative led jointly by ESA and NASA (ACIX II: the Second Atmospheric Correction Inter-comparison Exercise).

Dr Moritz Lehmann (Xerra and the University of Waikato) is participating in ACIX II by providing ground validation data from New Zealand lakes. Our nation’s remote location in the southern hemisphere provides a rare opportunity for data collection in a vastly under-sampled part of the world. Moreover, our country’s diverse environment (in terms of geology, topography, soil types, and anthropogenic pressures) produces a plethora of lake types and atmospheric conditions, which provides a useful challenge for generating globally-applicable methods for atmospheric correction.

The data Moritz has provided includes lake-surface spectral measurements of reflected sunlight (i.e., the same quantity measured by satellites but without the confusing influence of the atmosphere). This ground-truth data represents the ‘gold standard’. If the atmospherically-corrected satellite imagery matches the ground-truthing data we know that the correction method used is accurate.

Collecting ground-truth data

The trick to collecting the best ground-truth data is to be on a lake under a cloudless sky on the same day as a satellite passes over to take an image. Landsat 8 has a 16-day revisit period, and the two Sentinel-2 satellites return every five days on the same orbital path, meaning fieldwork can be planned ahead of time, in theory… the weather is the real wildcard in New Zealand.

Moritz and his team have so far collected two years of data from almost 100 lakes (Figure 1). For at least 20 lakes, the satellite orbits and weather conditions aligned to produce data suitable for ground-truthing (Figure 2).

Current international research

The information from New Zealand lakes has been combined with similar datasets from international collaborators. Developers of the atmospheric corrections methods receive only the geographic coordinates and the times of sampling from this pool of data. They will then be asked to estimate spectral reflectance at ground level from Landsat 8 and Sentinel 2 imagery.

Once the results are in, the atmospheric correction methods will be compared carefully and the results will be peer-reviewed, published and presented at various international conferences. The outcome will provide valuable guidance to the scientific community on choosing the right method for particular applications and directing future research effort.

Photograph of recording light measurements on Lake Ohau in Canterbury, New Zealand.

Figure 1: Light measurements on Lake Ohau (Canterbury) under perfect atmospheric conditions. Photo: Xerra Earth Observation Institute.

One map of New Zealand showing locations where data was collected, and a graph showing reflectance spectra from lakes at locations shown in the map.

Figure 2: Top: Map of New Zealand showing the locations of data collected simultaneously with overpasses of Landsat 8 and/or Sentinel 2 satellites. Bottom: Ground-truthing data (reflectance spectra) from lakes at locations shown in the map on the left. Credit: Xerra Earth Observation Institute.

Collaborators: Xerra, University of Waikato, NASA, European Space Agency

For additional information contact: Moritz Lehmann, 027 348 4590,

Funding by:
Lakes Resilience Programme (MBIE Grant UOWX1503)
Eye on Lakes Smart Ideas Project (MBIE Grant UOWX1802)
Xerra Earth Observation Institute Limited

Dr Uyen Nguyen (post-doctoral researcher coordinating data collection)
Warrick Powrie (Technician, fieldwork)
Dean Sandwell (Technician, fieldwork)
Daniel Bellamy (summer student, field and lab work)
Caitlyn Gillard (summer student, lab work)
Moshu Xie (summer student, fieldwork)

Water clarity improvements detected

By Xerra News Cat

A team led by senior scientist Dr Moritz Lehmann at Xerra and the University of Waikato has published an analysis of 18-year trends in lake water clarity in the Rotorua lakes. Water clarity is an important indicator of water quality where better clarity typically indicates fewer contaminants.

What makes this study special is that it combines human observations, taken from a boat, with observations from 700 km above the Earth’s surface by satellites. This combination of data sources allowed the researchers to assemble a data record from 1999 to 2017 for 23 lakes, a data volume far greater than available using traditional ground-based methods.

“We found that water clarity significantly improved in nine lakes over the 18-year study period,” said Dr Lehmann, “Most trends in the other lakes were also found to be positive, but not statistically significant.“

Among the lakes with significant water clarity improvements were Rotorua, Rotoiti, Tikitapu, Rotoma and Rotoehu. The researchers indicated that some improvements may be related to lake management actions such as alum dosing, water diversion and weed harvesting, but direct cause-and-effect relationships were not tested in this study. Lake Okareka was the only lake that showed a significant decline in water clarity.

Dr. Lehmann says that using satellite data to measure water quality attributes has become a reliable source of data for those conducting environmental monitoring programmes, such as local, regional and national governments and their stakeholder groups.

Snapshot of water clarity in the Rotorua lakes determined using a satellite image from 28 January 2018. Water clarity is expressed as Secchi depth.

Photo of a Secchi disk which is used for water clarity measurements

Water clarity is expressed as Secchi depth, which is the depth at which a Secchi disk (see picture) disappears from view when lowered into the water.

Moritz K. Lehmann, Uyen Nguyen, Kohji Muraoka & Mathew G. Allan (2019) Regional trends in remotely sensed water clarity over 18 years in the Rotorua Lakes, New Zealand, New Zealand Journal of Marine and Freshwater Research,

Moritz Lehmann on 027 348 4590 or

Evidence of changing river colours from space

By Xerra News Cat

The Clutha River is Aotearoa’s largest river (by discharge). It is a lifeline for communities in the dry Central Otago region, providing potable water and crop irrigation, with tourists marveling at its dark blue to turquoise water.

Snowmelt and recent rains have caused changes to the colour of rivers in Central Otago, as shown in the satellite images presented here.

3 November 2018
On Saturday, 3 November the Clutha appeared dark blue (above), whereas by the 13th is was more like turquoise (below).

13 November 2018
The Manuherikia River flows into the Clutha and is brown from silt run-off within its catchment. The confluence of the Manuherikia and Clutha rivers at Alexandra is marked by a sharp contrast in colours, but not much effect on the downstream colour of the Clutha.

23 November 2018
On Friday, 23 November (the next occasion the Sentinel-2B satellite passed overhead) much of Central Otago was covered in clouds, but luckily there was a gap in the clouds through which the confluence appears (left). Here, the much-increased flow of the Manuherikia is obvious from its penetration into the Clutha, and downstream the entire Clutha runs brown due to the mud carried by its tributary.
The discoloration of the Clutha downstream of Alexandra demonstrates the connective power of water – from the high country down to the lowlands, estuaries and coastal waters.
We reviewed images from when Sentinel-2B passed overhead on 28 November and could see clearly that the discolouration from the Manuherikia discharge had dissipated.

10 November 2018 – Clutha River sediment discharge emptying into the Pacific Ocean 75 kilometres south west of Dunedin.