The recent release of the joint Time, Inc., Google, the U.S. Geological Survey (USGS), and Carnegie Mellon University’s Create Lab Timelapse website in May of this year highlights once again the increased availability of a wide range of imagery – in variety of formats – to geospatial users across the Empire State. With aerial imagery becoming another market-driven commodity to support the expanding geospatial industry, consumers now have several options including either a la carte commercial off-the-shelf (COTS) products or more simply consuming imagery online – for free – as part of a growing number of publically accessible Cloud applications and map services.
Commercial Imagery Products
While imagery requirements to support large scale (1”=100’) planimetric feature mapping is often much more detailed and usually acquired through formal procurement, COTS imagery can routinely be obtained in the 1m – 2m resolution range, which is normally sufficient to support many general viewing and “what-is-where” geospatial applications across New York State. COTS imagery has never been easier and more cost-effective to acquire.
GIS mapping and viewing applications that use aerial imagery primarily as a means to provide context to larger-scale, more spatially accurate vector datasets such as tax parcel boundaries, building footprints, and street features can use COTS products. In the emergency response disciplines, rapidly deployed and developed COTS-quality imagery (+/- 1m – 2m resolution) has also become a standard in damage assessment for incidents such hurricanes, flooding, wildland fires, and other natural disasters.
Firms such as such as MapMart, WeoGeo, and TerraServer serve as brokers for several types of commercial aerial and satellite imagery – including Digital Globe GeoEye, and QuickBird products – which are sufficient to support “what is where” viewing applications in most government mapping programs. These commercial data warehouses also make available selected government image datasets such as the leaf-on National Agriculture Imagery Program (NAIP) photography. Commercial sites provide easy-to-use online forms to select areas of interest, imagery type/format, and cost estimates on the requested imagery. Commercial aerial imagery can also be bought directly from the aerial or satellite imagery firm (i.e., Digital Globe) but marketplaces such as MapMart and WeoGeo provide a broader range of options for the consumer. (Note: Georeferenced NAIP aerial imagery can be downloaded directly from Natural Resources and Conservation Service (NRCS) website. As part of preparing this blog post, I received a cost estimate from MapMart for two scenes of Digital Globe Precision Aerials (0.3 m resolution) imagery covering the entire Westchester County footprint – which proved to be very cost competitive and affordable.
Of course the ease and speed of purchasing COTS aerial imagery with or without detailed specifications does not come without potential issues or concerns. One, some commercial firms may only have imagery that is several years old for a selected “area of interest” or sometimes even more problematic is that a specific area may contain a combination of years of photography. Also, file formats, datums, or the ability to test (QA/QC) the imagery may not be possible and it is worth mentioning that commercial off-the-shelf aerial imagery products are typically not be used in the production or updating of large-scale planimetric vector datasets. Users measuring distances with COTS may take heed as depending on the scale and resolution of the imagery as calculated distant may contain an unacceptable amount of error depending on user requirements. Use and redistribution licensing restrictions should also be thoroughly reviewed.
Imagery as part of Cloud and Map Services
If users do not require a physical (local) copy of the imagery, there are also options to access web sites publishing aerial imagery as a service – for free – which can be “mashed-up” with local datasets in a variety of desktop and web viewing clients. One of the more notable aerial imagery map services in the Empire State is available through the New York State Digital Orthophoto Program (NYSDOP). In production since 2001, the program makes imagery available for both download and through OGC-compliant Web Map Services (WMS). Funded through a combination of federal, state, and local sources, many of most commonly developed NYSDOP image products across the state (particularly outside of urban areas) are 1ft and 2ft resolution imagery which are generally comparable to COTS available products.
A much larger and expanded source of online aerial imagery is The National Map Viewer (TNM) portal which provides several map services “containing orthorectified digital aerial photographs and satellite imagery” which are more than sufficient resolution to support “what is where” viewing applications. In additional to making high resolution imagery available, the TNM also provides viewing software that enables users to add local content – either as layers or map services. A somewhat similar “mash-up” system is the popular Google Earth viewer which provides imagery as base map and of course, the ability for users to add additional KML layers and WMS services. Other closely related products such as Microsoft Bing Maps offer developer tools to embed and make available imagery (Pictometry obliques) in business and government applications.
The new approach of providing both Data-as-a-Service (DaaS) and Software-as-a-Service (SaaS) in one interface – and for free – is increasingly empowering for organizations with limited resources or GIS capacity. Albeit at its core, ArcGIS.com is a fee-based product that offers similar functionality and does include free options if contributors make project maps accessible to the public. An exhaustive gallery of public facing maps – many of which include high resolution aerial photography as the base map AND can be modified and enhanced by anonymous users with local datasets – is available for viewing at the ArcGIS.com portal. Many of the maps can be used as a front-end to add local content for site specific projects here in New York State.
All said, the landscape has changed dramatically in recent months with regard to purchasing COTS aerial and satellite imagery which can used to support desktop and web-based geospatial applications. And the user community should expect options to only expand over the next several years as: 1) aerial imagery change detection technology continues to evolve (enabling consumers to purchase aerial imagery where it is really needed and/or physical changes have actually occurred) and 2) the next generation of smaller earth observation satellites promising a surge of commercial space-based imagery platforms combined with better web-based visualization and mapping systems that are ready to ingest and analyze near real-time imagery. To say the least of anticipated options associated with the budding drone and unmanned aerial planes/vehicles which will be used to support imagery and data collection.
If organizations have limited budgets, do not require a complete update of the imagery database or do not have other “hard” requirements (i.e., photography to support large-scale feature/planimetric mapping) COTS imagery can be priced very competitively and can be considered as a viable alternative in support of enterprise aerial imagery programs.