#Optical #SAR #Satellite tasking

Satellite tasking, and the increasing availability of on-demand Earth Observation data

For those who work in Earth Observation, satellite data is most familiar in archival form. This is how we have worked in the past; accessing data a few years or, with enough luck, maybe just a few months old. The typical applications for civilian satellite data use have always assumed the use of archive data. Only a handful of research projects could afford to buy newer data or, in rare cases, on-demand imagery.

On the other hand, popular culture is full of spy movies featuring scenes where MI6 are studying near-real-time satellite images of villains on the other side of the world carrying out nefarious acts—images obtained just a few hours previously. All these films show very high-resolution satellite data captured using optical sensors that were pointed on specific Areas of Interest, at a specific angle, and at the perfect time.

Today, we know this technology by the name of satellite tasking—and it’s now available to every one of us.

To learn more about satellite tasking, and to help me address some of the important questions in the sector, I recently spoke to Seulgi Son, Satellite Tasking Support Engineer at UP42.

What is satellite data tasking?

Satellite tasking gives users the ability to commission satellites and capture imagery for a specific area, according to particular parameters and project needs.

“We usually suggest tasking to customers who can’t find the image they need for their project in our existing archive collection,” Seulgi tells me. Satellite tasking allows users to define specific tasking parameters, such as area of interest, tasking time window, incidence angle value, acquisition mode (mono, stereo, tristereo), and maximum cloud coverage of the scene. “You have total freedom for that and total flexibility when defining these parameters, to ensure you get the perfect image that you need,” Seulgi adds.

What are the key use cases for satellite tasking today?

The most common use cases for satellite tasking besides government and military projects related to emergency response, where large organizations need to assess damage related to snowstorms or wildfires, for example. Another is vegetation management for railways, power, and utilities, where satellite data can be used to detect trees growing too close to critical infrastructure (like overhead electricity transmission cables), causing risk.

It is likely that new, emerging use cases will soon start to be developed by the community, as the data’s potential is huge and the cost is beginning to become more affordable for many organizations.

How quickly can you get the data?

When it comes to SAR data, from Capella Space, for example, it is possible to task satellites to get data within a few hours, because cloud coverage is not an issue. For optical data, the lead time is typically several weeks.

“The process starts with a client requesting tasking for a specific Area of Interest and basic parameters—such as cloud coverage, how they want the image to be processed, what kind of image capture technique they need (like mono, stereo, tristereo), and what kind of spectral bands they are interested in,” Seugli explains.

“All of this information needs to be factored in, then the data provider uses all these inputs to verify what can be done within the necessary time period, given the weather conditions, and other tasking requests,” she continues. “Based on those inputs, we provide a feasibility study, which analyzes whether the tasking can be achieved within the original parameters and time period specified. If not, then we recommend potential changes to the request in order for the mission to be feasible.” Cloud coverage is a huge factor, and although satellite companies massively invest in accurate weather models, it cannot be fully predicted. When the mission is approved, a connection is made to the satellite via Application Programming Interface (API), and a request is made for the data to be captured.

What can we expect from satellite tasking in the near future?

Satellite tasking is gaining some serious interest from the industry. One of the most critical aspects is being able to address emergency use cases.

“A company like UP42 has the team and infrastructure to ensure we are always ready to process urgent requests,” Seulgi tells me. The company is now focused on improving the overall experience for customers who need to obtain the data as soon as possible—as it might be critical for emergency situations. “To achieve that, we are working on APIs for automatic processes to enable the customer to receive notifications and status updates on where their images are in the pipeline, and when they will be available to access.”

Why should we care about tasking?

Earth Observation is going to be used in more and more advanced use cases, powered by the development of Geo AI and the increasingly wide availability of satellite data sources. Any geospatial analysis can only be as good and as up-to-date as the input data, which means that sooner or later everyone working in Earth Observation will be forced to consider satellite tasking. At the same time, as the competition between satellite companies grows, we can expect increasingly competitive pricing models, which will make tasking more available to the geospatial community as a whole. To stay ahead in the industry, it’s worth exploring right now.

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What is the difference between othophotos, orthophotomaps, orthomosaics and true orthophotos?

The science of photogrammetry has been developing for more than a century. Initially being fully analogue, it is gradually being digitalized for the past 30-40 years. Back then, it was a field understood and practised by a fairly small and closed group of engineers. The data was used mainly by governments and the military, and it was extremely expensive.

Today, the science of photogrammetry is in a totally different place due to the rise of drones over the past 7-8 years. Photogrammetry is now practised every day by hundreds and thousands of people around the world. They fly drones, capture the data, and process it seamlessly to get orthomosaics and Digital Surface Models (DSM). This helps them greatly in farming, construction, urban planning, energy, mining, and many other sectors. The drones and so-called “low-altitude photogrammetry” is ubiquitous.

The important terms

What I’ve noticed though, is that when you commoditize a field of engineering, the previous scientific terms start to live their own lives. Also, I have noticed that some of these terms have a slightly different meaning in different languages. Below I will try to define some key terms that you may see out there. Some of the terms apply mainly to the traditional photogrammetry and some apply more to the low altitude photogrammetry. Don’t worry, I will explain it all to you!

Orthophoto (left) vs. True orthophoto (right). source: nFrames SURE Software

Orthophoto:

Firstly, Orthophoto is an effect of photogrammetry processing that uses the Digital Terrain Model (DTM), typically seen in the traditional airborne photogrammetry. In orthophotos, you will often see an effect where the terrain representation is very accurate, but you will see a tilt in the buildings and other tall structures which is an effect of using DTM that only maps the natural shape of the earth (excluding vegetation and all man-made objects and structures).

True Orthophoto:

True Orthophoto, on the other hand, is processed using Digital Surface Model that maps every shape and object visible on the ground (including vegetation and man-made objects). True Orthophoto gives a vertical view of the earth’s surface, eliminating building tilting and allowing a view of nearly any point on the ground.

Traditionally measuring Digital Surface Model has been extremely difficult and expensive. It is typically done using LiDAR or ground measurements. On the other hand, Digital Terrain Models were widely available based on generalized countrywide elevation models. Therefore, True Orthophotos used to be very expensive to make and hardly available. These two products typically refer to the traditional airborne photogrammetry because according to the standards in many countries, they are required to be done using a metric camera and perfectly nadir images. It is, however, typically not the case in low-altitude drone photogrammetry.

Example of Leica ADS40

Orthomosaic:

The product of drone photogrammetry is typically called orthomosaic. In reality, an orthomosaic is similar to True Orthophoto (as it is generated using Digital Surface Model), but typically not based on a metric camera (in which focal length and internal dimensions are precisely known and calibrated), as these are expensive and not widely available for UAVs. Additionally, orthomosaics can be generated based on both nadir and oblique imagery.

Drone-based Orthomosaics are generated based on the Digital Surface Model which is not done as a separate survey as in the case for traditional airborne photogrammetry. In drone photogrammetry, the DSM is generated based on the 3D point cloud which is the initial product of the data processing. This technology is developed and used by Pix4D which monopolized low-altitude photogrammetry around the world.

In some geographies, orthophoto and true orthophotos that are entirely done according to local official standards (typically traditional airborne photogrammetry) should be submitted to national geodesy and cartography resource repositories. In these countries on such data is accepted as an official geodesy and cartography documentation, which might have consequences e.g. when using the data in court.

Orhophotomap by U.S. Geological Survey

Orthophotomap

Last but not least is the term known as an orthophotomap, which is very often used interchangeably with orthophoto and orthomosaic. However, the literature review says that it should be defined as orthophoto transformed to digital or printed map format which typically has map elements such as map grid, scale, north arrow, title, etc.

The EndNote

I hope that this post clears a bit the terminology to those who are confused. Please let me know in the comments if this is how you define these terms in your country or there are any differences. I look forward to opening this discussion and seeing your comments.

 

What is satellite data tasking?

Satellite tasking gives users the ability to commission satellites and capture imagery for a specific area, according to particular parameters and project needs.

“We usually suggest tasking to customers who can’t find the image they need for their project in our existing archive collection,” Seulgi tells me. Satellite tasking allows users to define specific tasking parameters, such as area of interest, tasking time window, incidence angle value, acquisition mode (mono, stereo, tristereo), and maximum cloud coverage of the scene. “You have total freedom for that and total flexibility when defining these parameters, to ensure you get the perfect image that you need,” Seulgi adds.

What are the key use cases for satellite tasking today?

The most common use cases for satellite tasking besides government and military projects related to emergency response, where large organizations need to assess damage related to snowstorms or wildfires, for example. Another is vegetation management for railways, power, and utilities, where satellite data can be used to detect trees growing too close to critical infrastructure (like overhead electricity transmission cables), causing risk.

It is likely that new, emerging use cases will soon start to be developed by the community, as the data’s potential is huge and the cost is beginning to become more affordable for many organizations.

How quickly can you get the data?

When it comes to SAR data, from Capella Space, for example, it is possible to task satellites to get data within a few hours, because cloud coverage is not an issue. For optical data, the lead time is typically several weeks.

“The process starts with a client requesting tasking for a specific Area of Interest and basic parameters—such as cloud coverage, how they want the image to be processed, what kind of image capture technique they need (like mono, stereo, tristereo), and what kind of spectral bands they are interested in,” Seugli explains.

“All of this information needs to be factored in, then the data provider uses all these inputs to verify what can be done within the necessary time period, given the weather conditions, and other tasking requests,” she continues. “Based on those inputs, we provide a feasibility study, which analyzes whether the tasking can be achieved within the original parameters and time period specified. If not, then we recommend potential changes to the request in order for the mission to be feasible.” Cloud coverage is a huge factor, and although satellite companies massively invest in accurate weather models, it cannot be fully predicted. When the mission is approved, a connection is made to the satellite via Application Programming Interface (API), and a request is made for the data to be captured.

What can we expect from satellite tasking in the near future?

Satellite tasking is gaining some serious interest from the industry. One of the most critical aspects is being able to address emergency use cases.

“A company like UP42 has the team and infrastructure to ensure we are always ready to process urgent requests,” Seulgi tells me. The company is now focused on improving the overall experience for customers who need to obtain the data as soon as possible—as it might be critical for emergency situations. “To achieve that, we are working on APIs for automatic processes to enable the customer to receive notifications and status updates on where their images are in the pipeline, and when they will be available to access.”

Why should we care about tasking?

Earth Observation is going to be used in more and more advanced use cases, powered by the development of Geo AI and the increasingly wide availability of satellite data sources. Any geospatial analysis can only be as good and as up-to-date as the input data, which means that sooner or later everyone working in Earth Observation will be forced to consider satellite tasking. At the same time, as the competition between satellite companies grows, we can expect increasingly competitive pricing models, which will make tasking more available to the geospatial community as a whole. To stay ahead in the industry, it’s worth exploring right now.

Do you like the article? Subscribe to our monthly Geoawesome Newsletter

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