This article was originally posted on Filling Space.
Geospatial imagery provides valuable information about Earth’s surface which can provide useful insight. Two common platforms for sensors are satellites and aircraft, each of which has benefits and drawbacks. In some cases, imagery from the two platforms may be combined to benefit end-users. To learn more about the two platforms’ differences, we spoke to Katie Fitzsimmons, who is the Reseller and Channel Manager for the HxGN Content Program. The program is a part of Hexagon, which is a global sensor, software, and autonomous solutions firm.
What are the differences between aerial and satellite imagery?
Resolution, fidelity, and consistency are the leading qualities of the best geospatial imagery products. While data capture using aircraft may be a time- and resource-intense undertaking, aerial imagery offers more flexibility in data collection and higher resolution data products. With advancements in imagery technology, collecting large volumes of data such as an entire US state is possible within just a few days, making the data temporally consistent. Aircraft can be deployed when conditions are ideal, providing consistent data sets of high image quality that are not affected by atmospheric or terrain conditions. Pilots can adapt flight paths to find the best flight conditions, if necessary, and aerial data can be captured at very high resolutions as fine as 2.5 centimeters.
Airborne imagers have been flying for more than 100 years. Advances in sensor technology and data processing techniques have enabled the acquisition of ultra-high-resolution data products, processed to very accurate specifications. The fidelity of the data can be relied upon to make decisions that require a high level of accuracy in the imagery.
While aerial imagery has the advantage of collecting data on demand (i.e. post-disaster deployment), deploying aircraft and crews may be cost prohibitive. Similarly, the frequency of imagery collection for some areas may be low.
Aerial imagery is commonly the first choice for applications requiring highly accurate and consistent data sets. On the other hand, satellite imagery is practical for users who need high data frequency or have data needs for areas that may be difficult to access, highly remote, or dangerous.
Satellite imagery offers great frequency of data acquisition as the imagers are continually collecting data around the entire globe. Advances in satellite technology over the last decade have improved the resolutions available and increased the number of providers offering satellite imagery services. Typical satellite images offer resolution of one to five meters, with some satellites collecting down to 30 centimeters. Satellites also collect specific spectral bands in the electromagnetic spectrum to support different types of analysis (though at a lower resolution) to provide the user with more insights.
Due to continuous data acquisition, satellite imagery is collected under all atmospheric conditions. This may include clear skies, clouds, smoke, dust, and terrain conditions including snow, fog, or shadows. Satellites may offer a patchwork of different images collected at different times, creating varying temporal conditions through a wide geographic area. However, if a user requires data often and can accept data that is less consistent and resolved, satellite imagery products are well suited.
There is always a trade-off between resolution and cost, so knowing the intended use of the imagery before purchasing is crucial to ensuring you get the right aerial imagery data for your project. Spatial resolution impacts the level of detail, or size of a feature, distinguishable in the image. The higher the resolution, the more detail you will receive, but it will come at a higher price. Keeping your budget in mind, it makes sense to purchase the resolution and accuracy required for your project. Although there might be higher resolutions available, you might want to add additional criteria to your decision-making process, such as data quality, positional accuracy, and continuity of data supply.
How are organizations using imagery data to make better decisions?
With higher image resolution and better geospatial accuracy, organizations use aerial imagery for applications that require a high level of detail and data consistency. This is especially the case in industries like urban planning, engineering, utilities, transportation, telecommunication, and risk management. Aerial data is commonly used as a base map to plan, map, and manage assets or to extract further information from the data, either manually or with machine learning algorithms.
Aerial imagery is especially beneficial in areas where landscapes change quickly and users need to analyze assets such as roads, buildings, parking spaces, water bodies, and vegetation in tight spaces like urban canyons. Artificial intelligence companies have leveraged aerial data to automatically extract and label various features that help businesses strategically manage their assets or to conflate their maps. Leveraging aerial imagery with AI has also been used for calculating solar roof potential and property risk analysis.
Users who need geospatial intelligence for applications that don’t require high level of detail and accuracy but need more frequent temporal updates, such as agriculture and environmental analysis, can get sufficient and cost-effective information from satellite data. Many agriculture firms benefit from the frequency of satellite images to measure changes in crops. The US government relies heavily on satellite data to gain intelligence into areas around the world that they would otherwise not be able to access.
What factors should be considered when selecting an imagery provider?
Geospatial imagery is an indispensable tool for planning, designing, engineering, and decision making. When selecting a geospatial data product, it is vital to understand how differences among imagery can affect your project. These differences include variations in resolution, positional accuracy, quality and atmospheric artifacts, large-area seamlessness, and others. Selecting a trusted partner for geospatial data can trim costs, streamline processes, and boost project results.
With over 25 million square kilometres of data, the HxGN Content Program is the world’s largest library of orthophotos, digital surface models (DSMs), and stereo images. Since the program’s inception in 2014, the data has been used across many different industries. State governments have found value in moving to a licensed aerial data streaming product to reduce costs. More recently, the data has been used for 5G network implementation where providers used 3D city models derived from DSMs to plan their network infrastructure.
The HxGN Content Program covers the entire United States and most of Europe, collecting consistent, high-resolution images at 15 or 30 cm resolution according to pre-defined specifications. Entire states are captured during the same flying season which guarantees homogeneous data sets. Users can access the data on the online store for pixel download or through an aerial imagery subscription that enables streaming into any GIS application via WMS or WMTS protocols. The HxGN Content Program offers a 10-day free trial subscription for customers who want to experience the data’s high consistency and accuracy standards.