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Raster Data in the Client with NumpyTiles

By: Dan “Ducky” Little on October 06 2022

Planet imagery is data-rich, using 12 bits per pixel. Web browsers only display 8 bits per pixel. So how about using NumpyTiles and those extra 4 bits to do remote sensing in the browser?

Atmosphere: it’s the one thing that anyone who works with visual data has to negotiate. To enhance visual imagery at Planet, we use processing techniques, such as color corrections, reducing the effects of atmospheric haze, sharpening, or adjusting pixels near scene boundaries to minimize the effect of scene lines. For a Planet Basemap, our automated processing uses a “best scene on top” methodology to select the highest quality scenes for use in a mosaic. This means, when you look at a Basemap, say in Planet Explorer, you see sharp images that contain the lowest cloud coverage.

Performing spectral analysis RGB true color visualization
Performing spectral analysis using RGB true color visualization

You may, however, want to manipulate the image a bit further for your particular use. You may want to play with the brightness, contrast, or saturation to pull out some detail. Planet Explorer provides a tool to do so called the Enhance tool.

Image Enhancement Tool off Image Enhancement Tool hosted data folder or analytic basemaps
Using the Image Enhancement Tool, you can enhance any scene in hosted data folders or analytic Basemaps

Even more, when you use the Image Enhancement Tool, you’re not just making a prettier picture, you’re actually doing remote sensing. This is because the image you’ve loaded is the actual data: all 12 bits per pixel. The red, green, and blue pixel data are used to display the browser-friendly colors. The other data are free to be used to perform the enhancement.

How’s it done?

Web browsers are an amazing way to get data into the hands of users. In the last 10 years, mapping applications through the browser have exploded. That explosion has pushed a number of innovations in vector formats. It has become easier than ever to take large data files of parcels, lakes, collections of millions of points, and stream them into the browser.

The same evolution has not been available to the wide range of raster data. When we display raster imagery in the browser, we’re limited to eight bits of data that define a color. This is called a true, or natural, color because it conforms to visual expectations–the colors you see in the world, for example, green grass or gray pavement. That’s what you’d expect the browser to display: the colors needed for a visual representation of the world. All web-browser image formats are limited to displaying Red, Green, Blue, and some transparency, to display that image in true color.

Remote sensing in the browser

Given that the browser is limited to eight bits for each one of these channels, we reduce the imagery’s extra bands of color and bit-depth down, by applying a “color curve” and selecting the true colors to use in the browser. Our “global” color curve is designed to work across all types of Planet data. Of course, there is no one-to-one mapping from 12-bits to 8-bits. So while the satellite is capturing lots of rich data, the global color curve addresses the most common imagery situations. This means some of that data, if it’s rarely used for representing most of the world, will not be visible in the color curve we use. Some imagery, such as the desert image above, may look washed out. But Planet's satellites are far more capable!

The imagery still has additional data that would be useful to manipulate in order to do remote sensing right in the browser. Working with only the RGB bits in the browser limits the ability to do raster-data based calculations, such as NDVI, or to see the images past that 8-bit limitation. To pass the large imagery data required for analysis to the browser interface requires getting that additional data through the network. Cloud Optimized GeoTIFFs (COGs) have helped show the potential of in-browser analysis with tools like geotiff.js. But COG's are not optimized for the web and have some limitations:

  • COGs do not always have overviews. This then requires streaming the entire image into the browser from the server. Zoomed out, this means processing a lot of high resolution data for one view.
  • Varying compression algorithms can create decoding issues, including overwhelming the client's CPU.
  • COGs are not guaranteed to be in the same projection as the map, forcing the need for raster projection and opening the door for creating rectification issues.
  • Here at Planet, we needed a technique that enables efficient streaming of multi-band, multi-byte data without the overhead of parsing a TIFF in the browser. Our solution? NumpyTiles.

What is NumpyTiles?

NumpyTiles is an open specification that Planet published on GitHub, designed to be both easy to serve and easy to parse on the client. “NumpyTiles” is a portmanteau of both “NumPy,” the popular Python numerical library, and “Tiles,” which refers to slippy-map tiles. Each NumpyTile is a NumpyArray which is 256 columns wide, 256 rows long, with any number of bands represented as additional dimensions to the array. NumpyTiles is compatible with any slippy map specification (WMTS, XYZ, TileJSON, OGC API - Tiles, etc), as it is just an alternate output format, like PNG or JPEG.

Planet open sourced OpenLayers NumpyTiles (ol-numpytiles) library to serve as a reference implementation that anyone can use. A demo of how this works can be found in the official OpenLayers examples as well as Planet Explorer.

Examples in Planet Explorer

The Enhance feature in Explorer is powered by NumpyTiles. The browser loads the images as NumpyTiles and applies the enhancements dynamically, based on the user’s viewport. This dynamic segmenting and loading provides the full range of relevant details for the pixels being displayed. The result is a more descriptive visualization of the data.

Mount Fuji Dark Mount Fuji Light
When the global color curve is insufficient, say for dense coniferous forests, you can use the Image Enhancement Tool to adjust local views dynamically

This is accomplished by leveraging the OpenLayer native WebGL rendering chain and lowering the amount of abstraction between “NumpyTiles” on a tile server and the rendered formats. This improved output allowed us to experiment with enhancement methods. Beyond the dynamic color curve, we could now add Brightness, Contrast, and Saturation sliders to update the image in real time, giving instant feedback to the user as to how their changes affect what they are seeing.

No enhancement Old enhancement New enhancement
true color visualization with no enhancement true color visualization with old enhancement techniques true color visualization with new enhancement techniques

The Growing NumpyTile Ecosystem

TiTiler

Remember the old days when you prepared the raster data and then had to push a PNG of the file for display in the browser? Now, Titiler, pronounced tee-tiler (ti is the diminutive version of the french petit which means small), provides a set of simple python modules for building your own raster dynamic map tile services. TiTiler works with NumpyTiles, serving up any input data as NumpyTiles to be used in applications.

You can go even further, by using the Titiler.PgSTAC plugin to connect to a PgSTAC database and create dynamic mosaics based on a search query.

Unfolded Studio

Ready to conduct powerful geospatial data analysis from your browser? Unfolded Studio is a geospatial visualization tool that lets you create maps from your geospatial data, perform powerful analytics, share and publish maps, and much more. Check out their sample maps for inspiration. Their raster data support leverages NumpyTiles for rich interactions. This can be seen in their COG support, which uses TiTiler under the hood to convert COG’s to NumpyTiles, and their Planet NICFI integration, which uses NumpyTiles from Planet’s tile service.

Next steps

Check out the NumpyTiles spec and the OpenLayers Rendering 16-bit NumpyTiles JavaScript example. Let us know what you’re building on Twitter.


State of STAC

By: Tim Schaub on August 31 2022

STAC-ing up! We gathered statistics on over 550 million assets. Check out the summary of our project and register to be included in our next crawl.

The number of imagery providers hosting data online has increased over the years. Search interfaces and metadata formats have also grown to describe and provide access to that data. The SpatioTemporal Asset Catalog (STAC) specification aims to provide a unified framework for describing and linking to earth observation data, with the goal of increasing the interoperability of search tools and making it easier to access the data.

Since its release in May of 2021, the specification has been gaining popularity, with massive archives of publicly accessible geospatial data being hosted with STAC compliant metadata. The USGS hosts STAC metadata for the entire Landsat Collection 2 archive. Microsoft’s Planetary Computer provides a STAC API with access to imagery archives of Landsat, MODIS, Sentinel, and more.

Planet sees STAC as a key component in making earth observation data more accessible to developers, and helping advance it is a core part of our “Open Initiatives” as previously described. STAC’s adoption has felt very rapid, but we wanted more concrete metrics to establish a baseline for its actual adoption. Building up knowledge of how data is exposed as STAC can help us understand how the standard is being used and how mature various extensions are. This, in turn, can help us prioritize what we work on to increase its uptake. So to better understand how STAC is being used, we recently deployed a crawler to visit publicly accessible STAC endpoints, recording millions of statistics about the catalogs, collections, items, and assets linked from those endpoints.

STAC in a Nutshell

The STAC specification describes a few different resource types: catalogs, collections, and items. Items represent the individual spatio-temporal data entries and have references to the data assets. Collections are used to group similar items. Catalogs are the top-level entry and can also be used as sub-groupings of collections or items.

STAC implementations come with two different flavors of interface: static files and API. The static flavor can be thought of as an online folder or directory of JSON documents linking to one another. The API flavor is designed to provide more efficient pagination through large collections of items and may provide more advanced search functionality.

Crawl Summary

Starting with just 27 endpoints, sourced from the amazing stacindex.org, our crawl visited over 120 million items, spread across almost four thousand collections. We gathered statistics on over 550 million assets referenced by those items. About 97% of the collections were from static catalogs, while over 99% of the items and assets came from STAC API implementations.

planetarycomputer.microsoft.com/api/stac/v1 landsatlook.usgs.gov/stac-server eod-catalog-svc-prod.astraea.earth stac.amskepler.com/v100 meeo-s5p.s3.amazonaws.com/catalog.json globalnightlight.s3.amazonaws.com/VIIRS_npp_catalog.json nasa-iserv.s3-us-west-2.amazonaws.com/catalog/catalog.json earth-search.aws.element84.com/v0 pta.data.lit.fmi.fi/stac/root.json franklin.nasa-hsi.azavea.com 10k 100k 1M 10M 100M
Top ten catalogs ordered by number of assets (log scale).
Static API Total
Catalogs 10,084 26,041 36,125
Collections 3,736 131 3,867
Items 1,077,616 122,258,062 123,335,678
Assets 1,497,447 550,133,772 551,631,219
Counts of catalogs, collections, items, and assets crawled, organized by implementation type.

The numbers suggest that people use collections far more frequently in static catalogs, presumably providing a way for users to explore reasonably small batches of items. While the STAC API implementations are dominated by catalogs with relatively small numbers of collections. Those API collections include many more items compared with their static counterparts. Because the STAC API provides search capabilities, catalogs and collections don’t need to be used as navigational aids in finding relevant items.

STAC Versions

The core STAC specification reached a stable 1.0 version in May of 2021, and the STAC API specification had its first release candidate toward 1.0 in March of 2022. Of the catalog, collection, and item resources we crawled, 88% conform with version 1.0.0. About 12% are still using version 1.0.0-beta.2. And a few stragglers are still on versions 1.0.0-rc.2, 1.0.0-rc.3, and 0.8.1.

Version Catalogs Collections Items
1.0.0 35,984 3,258 108,967,770
1.0.0-rc.3 0 0 10,000
1.0.0-rc.2 2 0 0
1.0.0-beta.2 123 597 14,352,545
0.8.1 16 12 5,345
Counts of catalogs, collections, and items organized by STAC version. These counts don’t distinguish between STAC API versions and core STAC versions.

It is encouraging to see the number of implementations that comply with the stable 1.0.0 version. Perhaps those still using an earlier version have a path to upgrade.

STAC Extensions

The core STAC specification limits itself to describing the spatial and temporal aspects of the data—specifying metadata fields for the geographic location and time range associated with the data. STAC extensions provide a way to add information specific to a given domain. Extensions exist for adding metadata specific to electro-optical data, for adding additional coordinate reference system information, for adding detail about raster bands, and more.

Of the 120 million STAC items crawled, 86% referenced at least one extension to the STAC core. In total, 46 different extensions were used by the catalogs, collections, and items visited in the crawl.

This information collected on extension usage should be useful to help give real metrics to establish the proper maturity classification of proposed extensions—suggesting which might be candidates to graduate to a stable classification or which might be candidates for deprecation due to lack of use.

STAC Asset Types

Assets in STAC provide access to the underlying spatio-temporal data. For STAC items representing satellite imagery, the assets could be GeoTIFF rasters. Items may have assets that refer to additional JSON or HTML documents. The STAC asset metadata includes a “type” property advertising the asset media type. Values like “image/tiff” represent a generic TIFF image; “image/tiff; application=geotiff; profile=cloud-optimized” represents the Cloud Optimized GeoTIFF variety.

Asset Type Count
application/json 101,831,216
application/xml 87,647,164
image/tiff; application=geotiff; profile=cloud-optimized 75,945,405
image/png 72,572,728
image/jpeg 50,259,307
text/plain 41,762,282
text/html 41,139,833
image/vnd.stac.geotiff; cloud-optimized=true 39,807,777
application/x-hdf 16,489,141
application/netcdf 10,252,878
image/jp2 3,639,899
application/gml+xml 3,619,721
application/vnd.laszip+copc 3,313,116
image/tiff; application=geotiff 946,859
application/x.mrf 902,162
text/xml 620,780
image/tiff 402,485
application/wmo-GRIB2 143,509
application/x-ndjson 143,509
application/x-netcdf 127,042
(missing) 25,051
application/html 10,000
application/vnd.google-earth.kml+xml 9,249
application/gzip 9,249
application/geopackage+sqlite3 5,854
application/geo+json 2,846
application/vnd+zarr 1,119
application/octet-stream 569
application/x-parquet 411
application/zip 58
Asset type counts.

At first glance, it is surprising to see the high counts of asset types that refer to additional metadata – the “application/json” and “application/xml” asset types, for example. We had anticipated that STAC assets would refer primarily to the spatiotemporal data instead of additional metadata describing that data. As it turns out, many implementations use assets to point to additional metadata that either doesn’t fit into STAC or provides an alternate representation of the same metadata found in the STAC resources. In total, just under 50% of the 550 million assets could be classified as metadata assets as opposed to actual data assets.

Considering all of its varieties together, TIFF is the most common asset type, representing over 20% of all assets crawled. About 99% of the TIFF assets are advertised as GeoTIFFs. It is possible the remaining TIFFs are GeoTIFFs as well, but simply use “image/tiff” as their asset type. Of the GeoTIFFs, over 99% are of the Cloud Optimized variety. It appears that people are still not sure about what media type is appropriate for Cloud Optimized GeoTIFF (COG). Although there is not yet an officially specified MIME type for COGs, there is growing consensus around “image/tiff; application=geotiff; profile=cloud-optimized” as a candidate for specification.

Under the Hood

The service used to perform the crawl made heavy use of go-stac, which has been expanded with a full set of “crawler” utilities.

The go-stac project on GitHub.com

The crawling done by go-stac is now quite robust against errors and failures, and multiple end-points can be used, with a task queue to go through large amounts of data concurrently. The validate and stats commands in the go-stac command-line interface use the same crawling backend, so it’s now a great tool to use with large STAC catalogs.

The crawl results were stored in a BigQuery table, and we’ll work to make the resulting data available to the community. It will be great to see what other insights might come from this data.

What’s Next

We hope that reporting on real world implementations helps the community understand how the STAC specification is being used. We are looking forward to running another crawl and updating the results as more implementations are rolled out and the STAC spec continues to evolve.

While the linked nature of STAC makes it possible to crawl and gather statistics on publicly accessible resources, it is not the most efficient way to summarize this information – particularly for very deep collections and relatively small page sizes. We have proposed a lightweight stats extension for reporting counts of resource types, versions, extensions, and asset types accessible in catalogs and collections. In future crawls, when the crawler encounters stats like those described in the extension, it will stop crawling deeper and increment counts based on what is advertised in the stats metadata. The stats extension is not yet finalized, so try it out with your catalogs and API implementations, and share any feedback or contributions in our issue tracker.

And please upgrade to STAC 1.0.0 and STAC API 1.0.0.rc.1 and register on stacindex.org to be included in our next crawl!


Eroding Coastlines: A GeoSpatial and Computer Vision Analysis

By: Kevin Lacaille, Mansi Shah on August 04 2022

We are thrilled to announce that two of our very own DevRel software engineers, Mansi Shah and Kevin Lacaille, were selected to present a tutorial titled Eroding Coastlines: A GeoSpatial and Computer Vision Analysis at Scientific Python 2022 conference in Austin, TX.

Mansi Shah and Kevin Lacaill after presenting a tutorial titled Eroding Coastlines: A GeoSpatial and Computer Vision Analysis at Scientific Python 2022 conference in Austin, TX

According to their website, the annual SciPy Conference “brings together attendees from industry, academia, and government to showcase their latest projects, learn from skilled users and developers, and collaborate on code development.”

Participants of Mansi and Kevin’s workshop gained hands-on experience exploring some of Planet’s publicly-available satellite imagery using Python tools such as rasterio, numpy, matplotlib, scipy, and openCV, to analyze medium- and high-resolution imagery data. During the second half of the workshop, participants applied what they learned to identify and analyze instances of coastal erosion, one of the most pressing environmental and humanitarian challenges facing our planet today. The tutorial involved a combination of slides and hands-on, live coding with real-world publicly-available data in Jupyter notebooks – no previous experience with geospatial or computer vision Python libraries necessary.

Coastal Erosion – Why It Matters

Coastal erosion is defined as the loss or displacement of land on coastlines due to waves, currents, tide, wind, waterborne ice, storm impact, and other natural and unnatural forces. While the natural weathering of coastlines is normal, human-led activities such as coastal mining, infrastructure development, and construction can accentuate the issue. Let’s also not forget rising sea levels are a result of climate change. The IPCC states with high confidence that the Global Mean Sea Level (GMSL) has risen 3.6mm each year, on average, from 2006-2015. Risk related to sea level rise, including erosion along all low-lying coasts, is expected to significantly increase by the end of this century without major additional adaptation efforts. Long-term impacts of coastal erosion include loss of habitat quality, degradation of coral reefs, increased turbidity of water, reduced tolerance for communities in the face of natural disasters, and reduced sand volume. These environmental impacts are in addition to the millions of dollars lost and spent annually on coastal property loss, tourism collapse, and erosion control measures in the U.S. alone.

Inspired by Crawford et. al (2020), the case study for this tutorial analyzed a severe example of coastal erosion, centered on a small, 7 km (4 mi), coastal region in Kamalnagar, Bangladesh. This region is located in Southern Bangladesh, where the ocean (Bay of Bengal) meets a major inlet, the Meghna River. Coastal erosion in Bangladesh is a recurring problem, causing thousands of people to be displaced annually. In fact, coastal Bangladesh experiences erosion rates that are among the highest in the world.

Bangladesh coastline study area with map

The workshop began with some geospatial and computer vision techniques, then moved on to apply those techniques to detect and analyze coastal erosion. The workshop focused on:

  • extracting data from multi-band imagery
  • computing the normalized difference water index (NDWI)
  • using the NDWI to identify regions of water and land within the area of interest (AOI)
  • applying classical image processing and computer vision techniques to analyze coastal erosion

The folks attending the workshop created a data and image processing pipeline. Then they detected and measured the effects of coastal erosion in Kamalnagar, Bangladesh. They found that over the past 5 years the land had receded about 2 km (1.2 mi) and that the region had lost about 11 km2 (2742 acres) of landmass. On average, this translates to the region losing about 400m (1300 ft) of coastline and about 2.2 km2 (550 acres) of landmass, each year. In addition to identifying coastal recession, our analysis showed that the recession was speeding up year-over-year, consistent with what the authors of Crawford et. al (2020) had found.

Bangladesh land loss animation

The workshop demonstrated that not only can geospatial data be beautiful, but it can also be used for great scientific purposes. In this case, it can be used to identify areas critically affected by natural disasters, which are prime candidates for humanitarian aid.

Planet & Environment

Our planet is important to us. One of Planet’s ethical principles is to protect the environment: “we actively develop and support uses of our data, products and services that address the critical planetary crises of our time, from climate change to the loss of nature.” This carries into our work in Developer Relations. We reflect this deep care for the environment in our work. Whether our tutorial attendees are environmental scientists, geospatial experts, or completely new to the field, a key part of our role on team DevRel is to engage and empower developers. At Planet, we enable technical users to do amazing and intentional things with our data. We’re here to support the search for answers.

Next Steps

Kevin Lacaille presenting at SciPy 2022 conference in Austin, TX

Kevin and Mansi were excited to engage with users of Planet’s data and the broader Python developer community around technical topics and environmental issues that matter. This was Planet Developer Relations’ first in-person presence at such a conference since 2020. We’re looking forward to reconnecting with old connections and building new ones. And we hope to see you there! Mansi Shah and Kevin Lacaille presented their tutorial at the SciPy 2022 conference in Austin, TX on July 11, 2022 from 8:00am-12:00pm CDT. Watch their presentation on YouTube. Try your hand at the Coastal Erosion Jupyter Notebook.

Planet and Cloud-Native Geospatial

By: Chris Holmes on May 26 2022

Planet and cloud-native geospatial open source

After Sara’s announcement of our new blog, I have the honor of writing the second substantive post on this blog. I’ve been at Planet for a long time and have always felt developers are our most important users. So I’m pleased to share that just recently I shifted my role to become the Product Manager of the Developer Relations team that Sara leads. Most exciting for me is that we’ve expanded the scope of the team to include what we call “Open Initiatives,” one of which is “Cloud-Native Geospatial,” encompassing all the work I’ve been doing on things like SpatioTemporal Asset Catalogs (STAC) and Cloud-Optimized GeoTIFFs (COG), plus new topics like GeoParquet.

A lot of my time recently went into organizing the Cloud-Native Geospatial Outreach Event that happened last month. Planet was a top sponsor, and a number of Planeteers gave talks. It’s super cool to watch the videos of the talks and to see how the community just continues to explode. With over 1600 registrations, I think we’ll see another jump in momentum after the event. I wanted to share a bit about Planet’s pioneering role in Cloud-Native Geospatial, as well as what we’re working on next and why we’re excited about this great ecosystem.

Planet and the genesis of Cloud-Native Geospatial

Planet was lucky to be among the first “cloud-native” satellite imagery providers (perhaps even the first). It was really a matter of timing, as Planet was founded right when any sensible Silicon Valley startup trying to achieve scale moved to the cloud. At that time, a standard image processing pipeline would involve image processing experts using desktop software to produce the imagery for customers. But Planet had huge aspirations of scale, with the mission to “image the whole earth every day” at the center of what everyone did. The amount of data coming in from Planet’s planned constellation meant that everything needed to be automated. So Planet just built its data pipeline and data hosting platform out right, and became a big supporter of the “cloud-native geospatial” movement before it even had a name.

The movement clearly started with the advent of the Cloud-Optimized GeoTIFF, which Planet played a key role in creating. The idea behind COG was discussed and built out in the AWS Landsat Public Dataset project, with Planet as a key contributor. Then it came together as a standard in a meeting I remember at Planet headquarters. We had a whiteboard session with Frank Warmerdam of GDAL fame, Matt Hancher who co-founded Google Earth Engine, and Rob Emanuele who led RasterFoundry at Azavea and now leads engineering on Microsoft Planetary Computer. We wanted a format that Planet could produce and that would be streamable into these two new cloud-native geospatial compute engines. And one that is ideally backwards compatible with a standard GeoTIFF, so it would still work for local workflows. Planet then funded Even Rouault to create the original specification and document the GDAL drivers.

Planet also worked on the evolution of SpatioTemporal Asset Catalogs (STAC), which started when Radiant Earth convened a diverse group of geospatial experts and organizations in Boulder, CO to collaborate on the interoperability of data catalogs. I recently posted on the history of Planet’s support of STAC. Planet’s role in STAC is one of the things I’m most proud of, and it’s fun to see it integrating into Planet’s API’s.

Why we support Cloud-Native Geospatial

Planet supports cloud-native geospatial because our imagery must be much more accessible to have the impact we aspire for. I’d like to explain a bit more as to why we support this ecosystem.

There are two critical economic shifts transforming the world:

  • The Digital Transformation, where organizations are using Big Data and Artificial Intelligence to understand what they do and to do it more efficiently
  • The Sustainability Transformation, where data about our planet is key to valuing natural systems in the economy

Geospatial Data is at the Center of Two Global Economic Shifts: DIGITAL TRANSFORMATION and SUSTAINABILITY TRANSFORMATION

Geospatial Information is useful for many organizations found in either or both of these movements. But the benefit will not be realized if everyone must become experts in remote sensing and GIS. It is incumbent upon us to make information about the earth accessible and integrated into the workflows people use everyday. And the biggest challenges always need more data sources, combined in insightful ways. Planet’s APIs and data formats need to be in the formats, tools, and channels used to create solutions that make a difference.

Cloud-native geospatial has the potential to make geospatial data far more accessible within existing workflows and architectures. By doing so, users don’t need to be experts in remote sensing and GIS. They just need to understand how to work with data.

Making Planet’s data more accessible to developers

Planet is working hard to ensure the developer experience is as solid as possible. The headline news of 8-band data availability is certainly cool, but what I’ve personally found especially impressive is how the team has greatly improved the quality of the imagery and reduced the complexity to access it. Improvements in our data pipeline include better alignment between pixels, a reduction in the number of artifacts, and a sharpening of the visual quality. And the new PSScene product simplifies and future-proofs how users and developers access imagery. Not quite as new, but seeing substantial adoption, is the Subscriptions API, which greatly simplifies the development time to integrate any monitoring workflow with Planet. Another great feature is the new harmonization tool, one of the key operations for Planet’s delivery tools in providing full Analysis Ready Data in an On-Demand workflow. Together these improvements are a huge step towards data that “just works,” enabling developers to order a atmospherically-corrected, pixel- and sensor-aligned stack of imagery for time series analysis without having to even think about all the complexities of remote sensing.

The next frontier in making Planet even more accessible to developers is the higher level data products that directly extract insights from satellite imagery. For example, Planet offers our Road and Building Change Analytics and what we call “Planetary Variables”, including Soil Water Content, Land Surface Temperature, and a proxy for Vegetation Biomass. These Planetary Variables go beyond just Planet’s imagery, fusing several different data sources, and will open up new use cases. Planet moving further up the stack, and into the “vector” area of geospatial, means much more access for new developers. And there are some interesting interoperability opportunities that we hope to contribute to.

Access the Planetary Variables Viewer by going to https://maps.vandersat.com in a supported browser (Google Chrome or Mozilla Firefox). Log in with your username and password.

What’s next for Planet and Cloud-Native Geospatial?

Planet data generates far more insight when it can be combined with other data. So we believe in helping create an ecosystem of tools and data that have interoperability at their core. One route is supporting tools like GDAL and Rasterio, which translate between any format. Another route is work toward the interoperability of the next generation of workflows, as COG and STAC do.

Building our team

Planet has recently been increasing its resources working on developer relations and cloud-native geospatial, including bringing on folks to work full-time on “open initiatives.”

  • Sean Gillies joined the developer relations team a few months ago. Planet is supporting his time on Rasterio, Shapely, and Fiona—some of the most important geospatial tools in the Python ecosystem. The other project he’s helping out on is a new version of Planet’s Python client and command-line library, which you’ll hear about soon on this blog.
  • Tim Schaub is one of the best developers I’ve worked with. You may know him as a leader of the open source OpenLayers JavaScript toolkit that Planet uses extensively. Tim has been going deep on Go, helping build Planet’s multi-source ARD product called “Fusion Monitoring.”

The developers relations team has also had a number of other great new hires, who you’ll hear from on this blog.

COG and STAC

In order for cloud-native geospatial to reach its full potential, COG and STAC will have to “cross the chasm” to mainstream adoption. To do so, we want to help everyone get a sense of just how much data there is in STAC and COG. If we can’t measure how much data is available in these new formats then we won’t be able to actually track progress and determine which of the various initiatives are working. To start, we’re focused on a crawler pointed at STAC Catalogs that reports back stats on the number of STAC Items, STAC Extensions used, and what format (COG, JP2K, Zarr, etc.) the assets are stored in. This, in turn, will help inform a new STAC extension making reporting easier, so we’re not having to hand crawl tens of millions of STAC records. We hope to report on the overall STAC and COG data holdings that anyone can access. We’ll work to integrate with STACIndex.org, which is where this idea originally came from.

To support this, Tim has revived the Planet go-stac open source library, getting it up to speed with STAC 1.0.0, and improving its crawling and validation capabilities. It’s now capable of very fast recursive crawling, with more improvements coming soon.

Planet Labs GitHub repository for the go-STAC utilities for working with Spatio-Temporal Asset Catalog (STAC) resources.

We are also starting to use the library internally to build and deploy Planet’s STAC Catalog of open data.

Cloud-Native Vector

Another area where we’ll be focused is the standards that can make our higher-level “Planetary Variables” data more interoperable. The goal is to have these available in “vector” data formats—the points, lines, and polygons that can be represented as rows in a database. Indeed, one end goal would be delivering daily information as simple tabular values against known geometries. This would mean a user already has the geometry of a state, county or even a field and they’d just get a daily update—say, of the plant biomass or soil moisture reading for the day.

Cloud data warehouses like BigQuery, Snowflake, and Redshift are driving a revolution in how organizations handle all of their data, and all have native geospatial support. So there is an opportunity to fit Planet’s daily variables about our earth directly into the workflows being used today. This has led us to helping seed efforts like GeoParquet. Javier de la Torre, from Carto, wrote a great overview introducing GeoParquet. Planet is working to build the community and the specification, and we funded the development of the GDAL/OGR reader that is included in GDAL 3.5.0. An interoperable format would enable us to publish data once and stream to a variety of cloud tools.

Next step: Join us

We’ve gotten this far by collaborating with others, and I think the opportunity to make geospatial more accessible is limitless. We hope others will join us in open collaboration. If you’d like to continue to get updates on what we’re up to in cloud-native geospatial, as well as all kinds of content about our API’s, tools, and the geo technical developer community in general, please follow our blog. And do check out our contributions to the Cloud-Native Geospatial Outreach Event, see the playlist on youtube for all the content.

Forward-looking Statements

Except for the historical information contained herein, the matters set forth in this blog are forward-looking statements within the meaning of the "safe harbor" provisions of the Private Securities Litigation Reform Act of 1995, including, but not limited to, the Company’s ability to capture market opportunity and realize any of the potential benefits from current or future product enhancements, new products, or strategic partnerships and customer collaborations. Forward-looking statements are based on the Company’s management’s beliefs, as well as assumptions made by, and information currently available to them. Because such statements are based on expectations as to future events and results and are not statements of fact, actual results may differ materially from those projected. Factors which may cause actual results to differ materially from current expectations include, but are not limited to the risk factors and other disclosures about the Company and its business included in the Company's periodic reports, proxy statements, and other disclosure materials filed from time to time with the Securities and Exchange Commission (SEC) which are available online at www.sec.gov, and on the Company's website at www.planet.com. All forward-looking statements reflect the Company’s beliefs and assumptions only as of the date such statements are made. The Company undertakes no obligation to update forward-looking statements to reflect future events or circumstances.

Subscriptions API for Daily Agriculture Monitoring

By: Matt Ballard on May 12 2022

Use the Subscriptions API for scouting, performance, precision applications, and more.

The Subscriptions API

At Planet, our satellites capture near-daily imagery of Earth’s entire landmass. You can use this data to build monitoring solutions for everything from directed field scouting to field performance monitoring to precision applications and more. The historical archive data that Planet has collected can be used to gather historical context, train models, and perform time-series analysis. For these persistent, always-on monitoring solutions, we provide the Subscriptions API to make it easier for you to integrate Planet data into your solutions.

With a single API call, the Subscriptions API allows you to subscribe to a continuous delivery of imagery to the cloud of your choice. You can set it up so you only receive data you’re interested in by making use of filters for your area of interest (AOI), time of interest (TOI), and more. As new imagery is added to our catalog, the Subscriptions API automatically checks to see if it meets your criteria. If it does, imagery is sent directly to your cloud storage destination. This significantly reduces the complexity of building a monitoring solution. You don’t need to build your own infrastructure or application for polling an API to search for newly available data.

Let’s take, for example, a solution for monitoring the health and performance of an agricultural field. Below is a sample API request over our field AOI for the 2018-2022 growing seasons:

        POST https://api.planet.com/subscriptions/v1/
        {
          "name": "Agriculture Field 12345",
          "source": {
          "type": "catalog",
          "parameters": {
          "geometry": {
              "coordinates": [[[-115.43197,32.924028],
              [-115.42354,32.923947],
              [-115.423616,32.93051],
              [-115.431959,32.930542],
              [-115.43197,32.924028]]],
              "type": "Polygon"
          },
          "start_time": "2018-03-01T00:00:00Z",
          "end_time": "2022-11-01T00:00:00Z",
          "rrule": "FREQ=MONTHLY;BYMONTH=3,4,5,6,7,8,9,10",
          "item_types": ["PSScene"],
          "asset_types": ["ortho_analytic_8b"]
          }
          },
            "delivery": { ... }
        }
Create subscription API example request (left); map of agriculture field AOI (right)

For the above order, the TOI spans from our start date, March 1, 2018, until our end date, November 1, 2022. If you are not interested in monitoring during off-season months, you can use Recurrence Rules (rrule) to filter for data from certain months. In the above example, we set a rule to send data only during the months between March (3) and October (10). This reduces the volume of data by not sending off-season data to your cloud.

The TOI is set to include data from previous growing seasons to use as a baseline for analysis of this growing season. For example, you could use the historical data to identify areas of persistent under-performance within a field. Or, you can use this data for time series analysis, identifying dates when events like tilling, planting, or harvesting occurred. As part of Planet’s Area Under Management (AUM) offering, you have access to Planet’s archive for the areas that you choose to monitor at no additional cost.

Time series analysis of average CIRE value in the field for the 2021 growing season; high values indicate significant vegetation and low values indicate recent harvesting

When you place an order for a timeframe which includes dates that have already passed, the order is “backfilled.” In other words, historical imagery from Planet’s archive for your TOI is sent to your cloud storage at the time of order. If your TOI extends into the future, imagery is delivered to your cloud storage as it is added to Planet’s catalog in what we call “forward fill.”

Raster processing with Subscriptions API tools

Remote sensing data requires a significant amount of processing to be turned into a usable form. Planet handles much of the preprocessing, including radiometric calibration, orthorectification, and more. To further help with preprocessing, the Subscriptions API supports a collection of tools that can prepare your data prior to cloud delivery. Below is a list of currently supported tools:

Tool Description
Harmonize Harmonize PlanetScope imagery with Sentinel-2.
Top of Atmosphere Reflectance (TOAR) Convert Analytic assets from radiance to reflectance.
Clip Clips imagery assets to your area of interest.
Reproject Reproject, resample, and rescale imagery products to a new projected coordinate system and resolution.
Band Math Apply mathematical expressions using the spectral bands of Planet imagery to produce outputs and indices.

These tools help to leverage PlanetScope data for visualization and analysis. For example, in agricultural field monitoring applications, the Clip tool is critical for reducing the size of the data because the area of a field is likely much smaller than the area of a PlanetScope scene. The Clip tool clips the rasters that are delivered to the extent of your AOI, as defined in your parameters when you create a Subscription. By clipping the data, you can reduce your cloud storage costs, analyze data faster, and visualize data in mapping applications more efficiently and effectively.

The Harmonize tool adjusts the Surface Reflectance measurements from PlanetScope instruments to align them with Sentinel-2. The tool is helpful when performing analysis across multiple PlanetScope sensor types from archive data because it minimizes scene-to-scene and sensor-to-sensor variability. This tool is especially useful when working with Dove Classic data as newer Doves, including SuperDoves, are already closely aligned with Sentinel-2. However, this tool has caveats and should be tested in your area of interest as it may not work as well in areas of rapid change (agricultural fields) or when scenes include bodies of water. For more information, please read: Scene Level Normalization and Harmonization of Planet Dove Imagery.

Another very useful tool for agriculture is Band Math. PlanetScope imagery captured by the SuperDove fleet includes 8 spectral bands which can be used for true color and false color visualizations. The Band Math tool in the Subscriptions API enables you to perform calculations using the different spectral bands and store the resulting values in a new raster. These 8 spectral bands can also be used to create indices such as:

Acronym Index Name Formula
NDVI Normalized Difference Vegetation Index ( NIR - R ) / ( NIR + R )
NDRE Normalized Difference Red Edge ( NIR - RedEdge ) / ( NIR + RedEdge )
CIRE Chlorophyll Index Red Edge ( ( NIR / RedEdge ) - 1 )
MSAVI2 Modified Soil-adjusted Vegetation Index 2 ( 2 * NIR + 1 - sqrt ( ( 2 * NIR + 1 ) ^ 2 - 8 * ( NIR - RED ) ) ) / 2
EVI Enhanced Vegetation Index 2.5 * ( NIR - RED ) / ( NIR + 6 * R - 7.5 * B + 1 )

Band Math creates an additional imagery output file which supports up to 15 bands with different calculations. Computation for calculating indices is completed before the imagery arrives in your cloud storage, reducing the time and steps you need to take to build your final solution.

Several images of this field with different indices

Cloud Delivery & Format

Now that we have created a Subscription for our AOI & TOI, and we have defined our processing tools, we are ready to deliver the data. When you create a Subscription you need to define your cloud storage destination from one of the supported delivery options. Using the File Format tool, you can also specify the file format for the rasters that are delivered as Cloud Optimized GeoTiffs (COGs). COGs are a Cloud Native Geospatial data format which is an efficient file format for on-the-fly processing and geospatial visualization. They enable any tool or client to request portions of the file based on the area of interest.

By utilizing the Subscriptions API, you are able to set up a regular delivery of satellite imagery to your cloud storage on a near-daily basis. The imagery can be filtered to fit your criteria and processed to your specifications prior to delivery. The Subscriptions API can reduce the cost and effort needed to prepare your data to be ready for visualization and analysis, ultimately reducing the time it takes for data to reach its end-users for decision making.

Workflow diagram for steps from creating a subscription to visualizing data

Next steps…

The Subscriptions API can be a powerful tool for use-cases where you need historical data and/or ongoing monitoring, making it highly valuable for agriculture monitoring. You can find documentation for the Subscriptions API in the Developer Center and sample notebooks for using the Subscriptions API in our GitHub repo. Also subscribe to our Developer Newsletter and get more information like this!