Disaster Risk Reduction, Imagery, Mapping

Satellite Imagery is A Powerful Visual Aid in GIS and Disaster Response

The earthquake events of August 21, 2018 which shook Venezuela, Trinidad and other neighbouring countries (https://www.usgs.gov/news/magnitude-73-earthquake-venezuela) reminded me that not all disasters can be predicted or come with a warning. Videos which showed the impact of the earthquake quickly filled my social media timeline, causing me to reflect on the training I had undergone as project manager for the International Charter Space and Natural Disasters (https://disasterscharter.org). This organization, once registered with, provides a series of support through the use of satellite imagery to assist in the aftermath of a disaster.

Satellite imagery is a form of remotely sensed data with proves useful in the occurrence of an unforeseen event and provides a powerful visual aid when utilized with a geographic information system (GIS). Disaster risk managers are better able to assess their region’s risk when they are able to compare pre and post disaster images.  This type of analysis enables relief workers to identify changes in the landscape, such as buildings which are no longer standing and roads which are obstructed. It is an efficient way to identify damage and conduct rapid impact and needs assesments. GIS supports the use of satellite imagery to locate damaged facilities, identify the type and amount of damage and begin to establish priorities for action.

As satellite sensors improve, satellite imagery is becoming more useful. One of my favourite places to explore satellite data is the USGS Earth Explorer Portal (https://earthexplorer.usgs.gov/). It provides an interface where one can search the available sensors to see the data that is available for a particular area of interest. The advantage of the USGS Earth Explorer is that it houses data from the Landsat Programme which has a 40+ year track record of image acquisition. It allows for free downloading of data over chronological timelines while providing a long list of satellites to choose from.

Additionally, capturing my interest for hours on end is the USGS Earth Now Viewer (https://earthnow.usgs.gov/observer). This viewer is truly remarkable as it shows the position of the Landsat sensor in real-time. It also gives a visual of the satellite images being collected when the sensor scans the earth.

The Landsat Program began with Landsat-1 in 1972 and Landsat- 9 is planned for 2023. Over the years, Landsat has enhanced the number of spectral bands, spatial resolution and spectral resolution. Landsat 1-3 sensors collected data in only 4 bands and at 60 meter resolution. Over time, this has improved, as Landsat 8 now collects in 11 spectral bands varying from 15 meter to 100 meter.

The Sentinel Satellites of the Copernicus Programme also provide free satellite imagery which can be downloaded at the Copernicus Open Access Hub (https://scihub.copernicus.eu/dhus/#/home). The Sentinel-2 provides some improvement to the Landsat data with sharper imagery of up to 10 meters. Sentinel-2 monitors more frequently with a revisit time of 5 days and captures land changes in 12 spectral bands, each ranging from 10 – 60 meters pixel size. The USGS Sentinel2Look Viewer (https://landsatlook.usgs.gov/sentinel2/viewer.html) allowed me to browse through some sentinel-2 imagery. I found relatively cloud free imagery of Montserrat (shown below) which was acquired on 12th April 2018. This is a plus as cloud-free imagery is not always available due to our location and climate.

With the assistance of a skilled technician, satellite imagery can be utilized effectively in disaster management especially during the response stages. By combining spectral bands and performing image classification techniques the capabilities of remotely sensed data can be fully utilized in disaster management.


Lavern Rogers-Ryan is a geospatial consultant specialising in disaster risk management and recovery. She is currently head of the GIS Centre within the Government of Montserrat. Learn more about geospatial services in disasters at www.lavernrogersryan.com.

Mapping, Uncategorized

Drones: Four reasons to use them in GIS and Mapping


I remember May 2010. Not only because it was the last time since the Montserrat Soufriere Hills Volcano’s dome collapsed, triggering a pyroclastic flow which completely covered the remnants of W.H. Bramble Airport. I remember May 2010 because I rode shotgun in a unique airplane.

This was an airplane which had a hole in the underside of it. Mounted and fitted in the hole was a camera. Not just any camera, it was a camera with unique specifications, designed for taking aerial photographs. After monitoring the weather for days and looking for a “space in the clouds” as it was termed, the mission began by travelling over to the neighbouring island of Antigua. I recollect that on the day of the flight we had to have all hands on deck, pushing the plane out of the hanger.



The flight plan was scribbled on a piece of paper, which the pilot displayed in front of him for the duration of the exercise. Riding shotgun, I took in the amazing vista of being up and above my beautiful island of Montserrat. We flew in an easterly to westerly pattern, for a number of days covering the island with images from the sky. The technician constantly gave instructions to the pilot to ensure that we were having a certain percentage of overlap in the images as they were being taken. Furthermore, the post-processing of the images was a lengthy one, as they had to be cleaned, corrected and geo-referenced in order to be used appropriately. After about six (6) months we finally had the complete set of imagery in our hands.

So much has evolved in eight (8) years. Aerial photographs are now been captured by Unmanned Aerial Vehicles (UAVs) or Unmanned Aerial Systems (UASs) commonly known as drones.

Here are four (4) reasons why I think drones should be used in Geographic Information Systems (GIS) and mapping:

Reduction in Cost – Drones provide a less costly way of acquiring remotely sensed data than the traditional method of a plane and pilot. There would be no need to need to hire a skilled pilot and pay exorbitant fees for the use of an aircraft and rental of a hanger, if drones are used. Drones provide an acquire once, use many times option, thereby significantly reducing cost.

Reduction in Risk – Although I thoroughly enjoyed the vista and scenery provided from the plane, there was an evident risk to human life. As the term “unmanned” suggests, drones reduce the risk to human life, as there is no man on-board. Moreover, drones do not possess human characteristics of becoming tired or getting distracted. These qualities do prove advantageous when collecting large amounts of data.

Reduction in Time – Drones provide a significant reduction in the time taken to acquire the imagery and the time taken to process the acquired image. Instead of taking months to see the output of one’s work, this is made available instantaneously as the data is being captured. Adjustments can also be made while flying, because the data can be visualized as it is being collected. Drones nowadays come equipped with global positioning systems (GPS) which allows for autonomous flying of pre-planned flight paths, thereby saving time in the field.

Increase in Quality – The output of drone images are becoming increasingly better. Drones can get closer to a scene than a plane can, thereby allowing for greater quality and detail in the imagery which is being captured. Appropriate specifications for the camera which is mounted on the drone, is key.

As reported, about a week after the May 3rd 2018 eruption of Hawaii’s Kilauea volcano, drones were deployed and started flying over the widening lava flows. This is thought to be the first time drones were being used to capture critical images and data above a volcano during emergency response efforts. (https://statescoop.com/amid-hawaiis-volcanic-eruption-drones-and-maps-revealed-hidden-fissure).

Utilizing newly acquired information and comparing it with pre-disaster information, gives a clear understanding of what transpired. Imagery collected from drones becomes a powerful resource once it is fed into a GIS. In emergency response situations, drones provide a quick overview with reliable visuals without putting first responders at risk.


Lavern Rogers-Ryan is a geospatial consultant specialising in disaster risk management and recovery. She is currently head of the GIS Centre within the Government of Montserrat. Learn more about geospatial services in disasters at www.lavernrogersryan.com.

Disaster Risk Reduction, GIS, Imagery, Mapping

Five (5) things GIS has taught me about Disaster Management

I am no stranger to the impact of disasters having survived Hurricane Hugo in 1989, and witnessed the Soufriere Hills Volcano disrupt everything I knew about life in Montserrat since 1995.

As I listened to the reports on the experience of our neighbouring islanders who were affected by the super hurricanes of 2017, Irma and Maria (which I now simply refer to as IRMARIA), I empathized.  Now as I watch reports of the experience of the residents of El Rodeo, Guatemala in dealing with the eruption of Volcan de Fuego which erupted on June 6, 2018, I am driven to share a bit of how my work can help countries manage disasters better.

Geospatial technologies have improved in recent years and are more efficient and reliable to enhance our planning, mitigation, preparedness, response and recovery from disasters.  The majority of data needed for these phases of emergency management is spatial, and once it is spatial it can be mapped and utilized effectively.

Over the years, Geographic Information Systems (GIS) has taught me a few things in relation to disaster management. Here are five (5) of them:

1.       Most emergencies don’t allow time to gather information.

2.       During an actual emergency there is no time for guessing or estimating, it is critical to have the right data, at the right time.

3.       Lack of appropriate information leads to poor planning and poor decision making.

4.       GIS provides a mechanism to centralize and visually display critical information during an emergency.

5.       GIS saves time, money and lives!

The road to recovery is often very difficult for anyone faced with loss after the impact of a disaster. Many of us on Montserrat however, built up our resilience as we reflect on the loss of homes – not just houses. We have embraced the challenge of recreating the places we lost. Unbelievably,  the Government Headquarters building in Plymouth was newly constructed and the Glendon Hospital was newly refurbished at the time of the eruption. Personally, I often reflect on the town centre which was thriving and bustling as it created jobs, enhanced livelihoods and held memorable spaces, such as “Evergreen Tree” and the “market” for social interaction.

A specialism in GIS allowed me the opportunity to support recovery efforts by utilizing data and producing maps that helped to manage evacuation paths, relocate families safely to shelters, assist in ash clean-up efforts by tracking progress and by utilizing the output of modelling scenarios to identify future impact areas.  GIS provides a mechanism to forge ahead and recover despite the impact of a disaster. Montserrat is now in a phase of re-development and GIS has contributed significantly to this. I do look forward to telling you more about how GIS can be used in disaster management.


Lavern Rogers-Ryan is a geospatial consultant specialising in disaster risk management and recovery. She is currently head of the GIS Centre within the Government of Montserrat. Learn more about geospatial services in disasters at www.lavernrogersryan.com.