The Right Geospatial Imagery for your Project

What is geospatial imagery?

They say that a picture says a thousand words. Well, if that picture is a geospatial imagery, then it speaks more than just a thousand words. It speaks a world of valuable data and information that we can extract through imagery services to help progress society and businesses alike. It is a tool that influences almost every industry vertical.

So what is this imagery that has such far-reaching effects on us?  Well, geospatial imagery refers to images of the Earth’s surface which we collect via satellites, drones and fixed-winged aircraft and other airborne vehicles. It is a form of visual representation of various geographical features. In short, it is a snapshot in time of a particular area of our planet. And when imagery services and GIS tools meticulously digitize the snapshot and convert it into layers of information, the imagery becomes a map which we can use to understand, relate, visualize, illustrate and analyze various geographical and sociological parameters.

From Clay Tablets to Geospatial Imagery

Despite its largely technical manifestation, geospatial imagery is not a modern invention. In fact, our relationship with it is very old. Since the earliest recorded human history, humans have resorted to the use of images and maps to store and communicate geographical information visually. The oldest known ones are preserved on Babylonian clay tablets and can be dated back to 2300 B.C. Then during the Renaissance age came and post that came the invention of the printing press by Gutenberg and later the development of the first photographic camera by Niépce. With this a new age in imagery-creation dawned, leading to more real and precise images of places on the earth. 

Today, as we stand in this digital age, satellites and airborne vehicles capture very high-resolution imagery. The imagery then undergoes the digitization of information using GIS software and modern imagery services. This has helped us to go beyond just the spatial reality of maps and create more refined information layers. As a result, the benefits that we derive from the present-day, high-quality imagery are immense.

history of geospatial imagery
Comparing geospatial data from 2300 BC to that after 4000 years, we notice how the science of imagery has taken a giant leap. Left image credit: @Ancientartifacts on Pinterest

Benefits of Geospatial Imagery

While it may be difficult to list out all applications of geospatial imagery, as we use today, the most obvious benefits to the human race have been summarized below:

Infrastructure Planning: 

Gone are the days of ground surveying of every little detail of any area. Today geospatial imagery, when converted into digital maps, allows remote ground referencing of assets and leads to the creation of highly accurate as-is plans. Such plans are used by planners and engineers to verify and validate project designs. This saves a considerable amount of time and money and conveniently produces highly accurate designs and plans.

Example: Urban city councils and municipalities use map features and data to understand the landscape in detail, this allows them to design road, residential areas, commercial zones and other infrastructures by optimizing space and traffic in the city.

Resource Exploration: 

By analyzing geospatial imagery of the earth’s surface, atmosphere and subsurface through imagery services, we have been able to venture into exploring those terrains that would have been otherwise impossible to access. With multispectral imagery, it is also possible to explore mineral deposits, subsurface water-tables, land washouts, vegetation covers and agricultural features without any heavy on-ground operations. 

Example: During the early stages of mineral exploration, it is important to know about the potential reserves in the area to gauge a profitable ROI for governments and E&P companies. In such scenarios, satellite remote sensing-based mapping in sync with a feature extraction and analysis solution provides the required data and saves valuable time.  

Emergency Response

Traditionally, humans have always grappled in the dark when it comes to dealing with nature’s wrath i.e. natural disasters. But today. with the help of geospatial imagery, we can mitigate it to a high extent. Geospatial imagery provides real-time maps, locational constraints and on-ground features which help chalk out disaster mitigation plans. These datasets can also be used to perform contingent operations in disaster-affected zones. 

Example: Detecting changes in imagery before and after an event is one of the quickest way available to understand and assess damage and enable rescue and rehabilitation measures. Moreover, imagery services help to extract data for disaster mitigation.

Navigation: 

One of the most important sectors influenced dramatically by the evolution of imagery is transportation. The availability of quality imagery helps in extracting all kinds of road features to create highly detailed navigation maps. Such navigation data makes routing and planning easy for organizations which operate map-driven vehicles on the road. Autonomous driving – the most remarkable invention in transportation is yet to come however feasibility has already been established by many companies and this has only been possible due to maps and geospatial imagery.

Example: With the recent evolution of assisted navigation and autonomous driving technologies, map companies and imagery services are now building highly precise or HD maps that contain detailed road geometry and attributes. This will lead to seamless and safe navigation experience

Types of Geospatial Imagery

As we can see, the benefits of geospatial imagery are far-reaching. As a result, there has been tremendous innovation in the sensors and the collection process through which geospatial imagery is captured. Based on the medium of collection, imageries can be classified into the following three broad categories – 

Satellite Imagery:

Satellite imagery, also known as earth observation imagery or spaceborne photograph, are images of Earth’s surface collected by imaging satellites operated by governments and businesses around the world. 

satellite imagery services
A satellite orbiting the earth to capture imagery. Image Credit: ESA

Aerial Imagery:

Aerial photography or airborne imagery are the images that are captured from an aircraft or other flying objects. Usually, fixed-wing aircraft and helicopters are used to capture aerial photographs of the area of interest. 

drone imagery services
Helicopter is the most common craft to capture aerial imagery

Drone Imagery:

Drone imagery is captured through an unmanned aerial vehicle (UAV) or uncrewed aerial vehicle which is commonly known as a drone. Drones are typically used to get very high-resolution imagery of areas of interest.

drone imagery services
Drone imagery is captured through flying drones over the area of interest

Geospatial Imagery characteristics that matter

Apart from the imagery capture medium, there are numerous other characteristics of an imagery that define its quality, applicability, precision and cost. The major ones which directly affect the outcome and quality of insights from imagery have been listed below – 

Spatial Resolution: 

It is defined as the pixel size of an image representing the size of the surface area being measured on the ground. This translates into the level of detailing you can see in the images. Depending on the image resolution, a city may fill an entire satellite image with grids of streets or it may be a mere dot on a landscape. Resolution is measured in cm per pixel or meters per pixel. Commercial satellites have a spatial resolution ranging from 30 cm to 30 m per pixel. To understand resolution in greater detail, you can read our post- ‘The Truth in Pixels‘.

Spatial Resolution
Landsat 8 satellite provide a city level macro-perspective captured during the September 2013 floods in Boulder, Colorado. Image credit: Jesse Allen and Robert Simmon, using data from the USGS Earth Explorer.
spatial resolution of geospatial imagery services
Imagery from WorldView-2 satellite show street by street details captured during the same flood. Image Credit: Worldview-2 ©2013 DigitalGlobe.

Positional Accuracy: 

Positional accuracy is the indicator or measure of how accurately a spatial object is positioned on the map with respect to its true position on the ground.  This has always been a major roadblock in capturing accurate imagery since it involves establishing a precise geolocation position using surveying equipment and then securing a visible ground marker exactly on the pre­-marked GPS point. However, over the years commercial providers have accumulated a large quantity of accurate ground control points that has helped calibrate create highly accurate imagery.

positional accuracy of geospatial imagery
A ground control equipment while capturing imagery with drone.. Image Credit: https://www.gpsworld.com/

Multispectral Bands

Most common imagery are in the visible range and they contain 3 bands of R, G, B (Red, Green and Blue). However, since the 1980s, satellites are able to record waves of frequencies outside of the visible spectrum. Since they record colors beyond the RGB spectrum, they are called multispectral imagery. 

The non-visible wavelengths can be used to detect features on earth’s surface that do not emit light in the visible spectrum. A whole new world of potential information can be leveraged to detect subtle differences and growth of features across a landscape like soil, vegetation, asphalt, minerals, water and even subsurface archaeological features like walls, subways, ditches, and natural subsurface features like mineral reserves, water reservoirs, geological strata, etc.

multispectral imagery
Imagery of Diros Bay, Mani peninsula, Greece. Left: 2.5-meter resolution, panchromatic CORONA. Center: 30-meter resolution, 7-band multispectral Landsat 5. Right: 0.5-meter resolution, 4-band multispectral QuickBird (showing the near-infrared band). Imagery courtesy the USGS and the DigitalGlobe Foundation.

Atmospheric Compensation: 

The quality and clarity of images are affected by atmospheric factors like cloud cover, precipitation, humidity, etc. which lead to scattering of light-waves and absorption from haze, dust, water vapor and particulates in the atmosphere. Therefore, imagery capturing has to consider atmospheric conditions and apply the required compensation for the same. 

Atmospheric compensation
Left: Before atmospheric compensation; Right: After Atmospheric compensation. Image Credit: DigitalGlobe

Vintage: 

Vintage of imagery refers to the age of the imagery i.e. the time when it was captured. This is important because imagery represents the ground truth of an area on a specific date. If one is using outdated imagery, it may lead to errors in the representation of objects and features as the on-ground situation might have changed since then. Hence there is a constant requirement to use the most fresh imagery to represent reality as close as possible. Most of the imagery sellers provide archival images which are less costly than real-time tasked images.

Vintage of geospatial imagery
Left: Albuquerque in 1935. Right: Albuquerque in 2009. Image credit: https://edac.unm.edu/image-archive/

Revisit Rate: 

The revisit rate period is the time elapsed between observations of the same point on earth made by the image capturing platform. Consequently, satellites tend to have a minimum and pre-defined revisit rate. In contrast, aircraft and drones have a flexible revisit rate. It’s beneficial to have the option of shorter intervals between revisit of images to really understand and characterize the rapid changes driven by human activity or unusual events in the area of interest. 

How your project parameters influence geospatial imagery and services selection

Well, if you are looking to work on a project that requires geospatial imagery, then it is advisable to first clearly identify the following project parameters. This will help you to shortlist the most suitable imagery and imagery services for your project

Area of interest:

The scale of your project is an important factor to consider while choosing the imagery source, type and imagery services. Note that if your project spans over a large area and doesn’t require large scale detailing then you can use low-resolution images. 

Application and associated features needed:

Depending upon the industry you are in and the associate application you want to address, you will have to ensure that you choose imagery with the most relevant characteristics like resolution, vintage and visible/spectral bands.

Project Budget:

Depending upon the budget allocated to the project you can choose imagery with optimum revisit rate, resolution, and other characteristics since the cost increases with resolution and revision. You will have to work out the features that one can compromise to remain within budget without failing the project objective.

The below table presents a succinct comparison of the characteristics of different types of imagery which you can use to understand the kind of imagery you might need for your project:

Imagery TypeSatelliteAerialDrone
Resolution 30 cm – 30 m 7.5 cm – 30 cm 1 cm – 10 cm
Positional
Accuracy
Proportional to
Resolution
Proportional
to Resolution
Proportional to
Resolution
Spectral
Bands
Depends on the
sensors present on
the satellite
Sensors can be
used on the aircraft as required
Sensors can be
fitted on UAVs as
required
Atmospheric
Compensation
Cloud cover,
precipitation etc.
affect the
imagery
Precipitation may
hinder imaging process
Not affected by
cloud cover,
moisture, etc.
Vintage Archive imageries are cheaper than
tasking imagery
Archive imageries are cheaper than
tasking imagery
Archive imagery is usually not
available
Revisit Rate Depends upon the
orbital rate,
not flexible
Needs a sortie/trip for
every revisit
Flexible and requisite revisit
available
Minimum
Request Area
In order of 
10 to 100 sq km
In order of 
1-10 sq km
No minimum
request area,
depends on trips

Where can you buy geospatial imagery?

There are numerous governmental and commercial organizations that produce, sell and resell imageries of different kinds. We list a few of these organizations below:

Satellite Imagery Sellers: DigitalGlobe, Airbus, Planet, NASA, ESA

Aerial Imagery Sellers: Nearmap, Eagleview, Blom, Geocam, Getmapping

You can contact us at Attentive AI and we will help you to source the most optimum geospatial imagery and imagery services for your project.

You have geospatial imagery. What next?

Now that you have got the imagery for your project, it’s time for you to derive maximum benefit and reap actionable insights from it. To do this you will have to extract map features and other attributes from the imagery. Now, even though this is one of the most important steps, it is time-consuming and expensive. However, our team at Attentive AI can make this process cost-effective and hassle-free for you.

Attentive AI has developed an AI-powered feature extraction engine, which simplifies this tedious task. You can request the extraction of any standard or custom features and attribute from your imagery from any source and get it delivered to you in the required file format through our platform or an API.

Feel free to reach out to us at Attentive AI with your feature extraction query and we will be glad to help you derive the maximum benefit out of your imagery.

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9 Responses

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