Color aerial "leaf off" ortho imagery for Massachusetts from 2019.
In spring 2019, MassGIS partnered with the U.S. Geological Survey for statewide, 15 cm resolution, 16-bit, 4-band (RGB-IR) digital orthophotos. Funding was provided by MassDOT, the Executive Office of Energy and Environmental Affairs, the State 911 Department, the Executive Office of Technology Services and Security (EOTSS) and the Massachusetts office of the Natural Resources Conservation Service (NRCS).
The data were delivered in early 2020 as 10,218 individual 1,500 m x 1,500 m tiles in a GeoTIFF format. To allow for easier distribution of this free imagery, MassGIS compressed the GeoTIFFS into the JPEG 2000 format, which retains the IR band. The tile naming convention is based on the U.S. National Grid (USNG), taking the coordinates of the southwest corner of the tile. See the Index layer.
Project specifications are based on the American Society of Photogrammetry and Remote Sensing (ASPRS) standards. The data were developed based on a horizontal projection/datum of NAD 1983 2011 UTM zones 18N and 19N meters and a vertical projection/datum of NAVD 88 (GEOID 12B) meters.
This digital orthoimagery was created to provide easily accessible geospatial data which are readily available to enhance the capability of federal, state, and local emergency responders, as well as to plan for homeland security efforts. These data also support The National Map.
These images can serve a variety of purposes, from general planning to field reference for spatial analysis, to a tool for data development and revision of vector maps. The imagery can also serve as a reference layer or basemap for myriad applications inside geographic information system (GIS) software and web-based maps.
Aerial imagery was acquired by Quantum Spatial, Inc. using Vexcel UltraCam Eagle M1 and M3 digital mapping cameras. Imagery was collected between March 24 and April 25, 2019, before most deciduous trees were in bloom, and while no snow was on the ground and rivers were at or below normal levels. The imagery was supplemented with the simultaneous acquisition of airborne GPS/IMU data, which captured the ground coordinate for the nadir point of each photograph. The imagery was exposed at altitudes between 7,200 and 8,500 ft above mean terrain across 183 flight lines.
Ground Control and Positional Accuracy
In order to post process the imagery data to meet task order specifications and meet ASPRS horizontal accuracy guidelines, Quantum Spatial used 132 ground control/check points that were distributed throughout the project area and were surveyed using GPS techniques. The x and y positions of where the check points fell on the orthoimagery were collected. These values were then compared to the surveyed control point x and y values. Horizontal accuracy tested 0.1 meters RMSEx, RMSEy and RMSEr.
Utilizing all four bands [red (R), green (G), blue (B), and near infrared (IR)], Quantum Spatial performed digital orthorectification using bilinear interpolation algorithms. This step resulted in spatial and radiometric transformation of the digital images from line/sample space into NAD 1983 2011 UTM zones 18N (for the western part of the state) and 19N (for the eastern part of the state).
Radiometric correction software and techniques created orthophoto files that minimize the appearance of image seams without loss of feature signature. Orthophotos were checked for geometric accuracy and image quality, and were tonally balanced to produce a uniform contrast and tone across the entire project. The individual overlapping orthophoto frames were mosaicked together.
JPEG 2000 Compression
MassGIS converted each GeoTIFF to an 8-bit JPEG 2000 (GMLJP2) format image using GeoExpress 10 software. These files maintain all four bands and were produced at a lossy compression ratio of 30:1, resulting in very minimal loss of image quality. Each image is approximately 13 MB, reduced from the 763 MB GeoTIFF, more suitable for distribution and download. MassGIS calculated statistics on the JPEG 2000 images in ArcGIS Desktop 10.7.1. All of the imagery is available for public use and distribution.
In addition to the information below, we have created a step-by-step, illustrated guide to help you connect to the webservice.
MassGIS created a tile service (cache), hosted at ArcGIS Online. This service type contains pre-rendered images to support fast visualization of large datasets. The cache uses the RGB bands and appears at scale levels 7 (1:4,622,324) to 20 (1:564). It is compatible not only with ArcGIS and web apps built with the ArcGIS APIs, but also third-party apps that use OGC protocols such as WMTS.[Source] The cache appears as a basemap choice in Oliver and all ArcGIS Online maps and apps, including the Massachusetts Interactive Property Map. ArcMap and ArcGIS Pro users can add data from ArcGIS Online and search for 'MassGIS 2019'. To add the service to QGIS, follow these instructions and for the URL enter:
https://tiles.arcgis.com/tiles/hGdibHYSPO59RG1h/arcgis/rest/services/USGS_Orthos_2019/MapServer/WMTS/1.0.0/WMTSCapabilities.xmlVisit the service's item details page for more information.
Use and Restrictions
No restrictions apply to these data. However, users should be aware that temporal changes may have occurred since this dataset was collected and that some parts of these data may no longer represent actual surface conditions. Users should not use these data for critical applications without a full awareness of their limitations. Acknowledgement of MassGIS would be appreciated for products derived from these data.
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